synsonics drums

stereo-pro synsonicsthom's modestly modded synsonicsle modèle rose


The Synsonics Drums are a lot of fun. I picked this up at a flea market for like 15 bucks, not knowing what it was. I thought: “cool, analog sounds! Probably can’t bend it much, but how can you go wrong for less than $20?” Well, i was right, there aren’t many “bends” inside, but hot damn! there’s a lot of mods! Individual volume, pitch, decay, distortion, etc.

UPDATE: June 2008 Be sure to check out Richard’s mods in the comments below.

Individual Outputs

1 Bass Drum (CH1)
2 Bass Drum (CH2)
3 Tom2 (click)
4 Snare (noise)
5 Snare (click)
6 Cymbal
7 Tom2 (tone)
8 Tom1 (tone)
9 Tom1 (click)

The toms and bass drum are made up of 2 sounds. A click and a tone. The snare is made up of a click and a noise wave. And i think the cymbal is just noise. You can wire up jacks to these points, with the jack’s ground going to the circuit’s ground for individual outputs, or you can wire up pots to these resistors for individual volume controls.

Accessory Jack

Mattel made an “accessory pedal” for the synsonics- a bass drum and hi hat pedal. The accessory jack is a 5-pin DIN jack, but don’t try plugging a MIDI cable into this thing. A better idea would be to make a custom cable with a male DIN connector on one end, and female 1/4 jacks on the other, so you can plug in standard drum trigger pedals. [EDIT: someone actually did this and says it works] Or you could bypass the DIN jack altogether, and wire up trigger jacks on the case (if you can find room).

synsonics- ACC jack pinout

5 – Ground
4 – Bass Drum trigger (connect to ground – pin 5)
3 – Hi Hat accent (connect to ground – pin 5)
2 – Sync Pulse Output: 16 pulses per quarter note (ppqn), 8V+, 15msec.
1 – Sync Pulse Output (Bass Drum): 1ppqn, 8V+, 15msec.

Important Note: The original diagram that was here had a pinout numbering system that conflicted with the pinout from the service manual. I have now changed the pin numbers to match the service manual. Also: the OUTSIDE VIEW diagram is looking at the front of the jack, and the INSIDE VIEW (from the service manual) is looking at the back of the jack. Thanks to RichardC64 for pointing this out!

Audio Sample

(mp3)Synsonics DemoMP3 – 1.53 Mb – 0:50
I’m trying to play synsonics and bent sk-5 at the same time. Thom is playing bent touch n tell. This is a good example of the decay mod on the synsonics.
(mp3)toy analog acidMP3 – 4:00
Toy drum groove. featuring thom’s modded synsonics, q-bent tom drums & analog ‘beww’ machine’s feedback drones.



Ok, i don’t even know where to begin. As you can see, I’m on the bottom of the board here. This might not be the easiest way to go about moding this thing. When you open it this way, you have to move the drum pads aside, and it’s a real pain in the arse to put it all back together. It might be better to go from the other side, but you do what ya gotta do.

I’ve marked 3 areas of the board. A,B and C. These areas seem to be where the most mods are. B contains the individual outputs. The above table has all the mods i’ve found (so far).

AH (pot) B8 Tom1 synth vol” means connect a potentiometer between point AH and point B8 for control of the synth volume for tom 1.

AG (output) nosie” means connect an output jack (hot) to AG (with jack ground to circuit’s ground) for an output of just one of the noise synths.

Experiment with different value pots. I used a 100K pot when i found these mods.

AH (pot) B8 Tom1 synth vol
AF (pot) AC Tom2 synth vol
AF (pot) AB Tom2 synth vol w/distorted click
AH (pot) B8 noise vol
AG (pot) A7 sustained snare rattle
AF (pot) C5 Tom2 pitch
Touch Triggers: Normal decay.

Resistance affects pitch and vol.

AG (pot or touch) C2 tom2 trigger (sustain)
AG (pot or touch) C1 cymb trigger (sustain)
AG (pot or touch) C1 tom1 trigger (sustain)
AG (pot or touch) C1 snare trigger (sustain)
AF (pot) AB, DG, DF, DS tom2 vol, with different clicks
AE (pot) CA, CD mix noise into tom2
AD (pot) AA, A5, AN, AO, etc. trigger synth tones. R=pitch
AI (random points cause chaos!) 1/32 note triggers of everything
AJ (pot) AA, C1, C2, C3, C4 snare also triggers tom1
AH (pot) A9 snare also triggers cymb
AJ (pot) AW snare decay plus click track
AJ (pot) A8 snare morphs into cymb
AG (output) nosie1
AX (output) nosie2


    Question about the Synsonic and other drum pads
    I am interested in purchasing an inexpensive drum pad with multiple pads and sounds. When I was researching, I came across what you wrote about the Mattel Synsonics thing (I found it on eBay for $19.95).  First I was wondering if I can straight up just plug it into an amp without messing with stuff and be good to go.  Also I see that this thing looks pretty basic but what drew me in was the decay feature that you said was very good.  I was just wondering if I could get more feedback about it.  I am just looking for a few drum sounds I can put through my amp with some effects or decay, or
    reverb.  I dont really need a bunch of built in rythms or something really hightech.  I was comparing it to some of the Rolands which I have decided are too expensive and then I found the Yamaha DD-50 which is less than the Rolands.  Some more info about the Synsonic and perhaps comparisons to the Yamahas or Rolands would be greatly appreciated.  
    Thank you very much.

  • yeah, the synsonics is a great little drum pad for the price.
    Will you be circuit bending or modifying it? Because the decay function i wrote about is not built-in, i had to modify the synsonics to get that. I’ll be updating the site soon, so check back for new samples. The only control that comes stock, is tuning for one tom.

    Yes, you can plug it into an amp. However, it doesnt have the usual 1/4″ mono jack. It has 2 RCA outputs, and one 1/4″ headphone stereo output. Some of the drum sounds are panned slightly left, and some panned right. Since the headphone jack is stereo, if you plug in a normal guitar cable to it, some of the drums will sound louder than the others. The best way might be to get a couple cables and adaptors, so you can go from double RCA to single 1/4″ (a Y-cable maybe).

    I think the synsonics will be similar to the yamaha drums, but the synsonics are ANALOG, whereas the yamahas are DIGITAL. Very different sounds.

    check out these virtual drum machines-

    good luck!

  • Excelent work on the mods. I’m gonna do some work on my synsonics and your mods page is a godsend. Just wondering if you’ve found any other mods. Also I am interested if there is a way to bypass the sequencer’s internal clock and feed it an external clock (from say an 808 or something with a +5volt trig).

    The question I had about the mods page was about the trigger section on section C of the circuit board diagram. You say that a touch trigger will trigger the sound, is that in refrence to the touch buttons of the sequencer or an alternative outside source. If so have you tried using these points as trigger inputs from an external source and using a potentiometer to basically control the sensitivity. I ask because I would love to make trigger inputs for the synsoncis but I don’t want to blow the unit by sending it voltage to a place it does not want to go.

    Anyways, thanks very much and keep up the good work.


  • Matia-
    It’s been a while since i’ve messed with the synsonics….. The stuff on my mods page is really just the tip of the iceberg. I haven’t gone any further, because in order to use all the stuff i found, i really need to recase the whole thing. So for now, it sits on my shelf until i have time to start a new project. Start with the mods i listed, and see if you can find any more in those areas. And please let me know how you do, this machine is one of the “best kept secrets” in the circuit bending world so far.

    External clock:
    There is most likely a way to do this, but it would take some work. You need to find the internal clock, figure out how it works (how many pulses per beat, what kind of pulses), and then build your own clock. I’m not sure where to start without the service manual…. The synsonics does have a tap tempo function, but i doubt it is accurate enough to be of any use.
    An easier way to make the synsonics sync up with other gear is to just make triggers for all the drums, and sequence it externally. The down-side to this is that you dont get to use the built-in 1/8, 1/16 and 1/32 note triggers that are so fun to play with.

    Touch triggers:
    When i say “touch trigger,” i’m using circuit bending lingo. A touch trigger could also be called a “body contact.” It’s when you have 2 points on the circuit, and instead of connecting them physically, like with a switch or button, you only need to touch each of them with your body. I haven’t tried yet, but i would think it’s entirely possible to just wire them up to buttons, using pots to control the sensitivity. (in this case, i think resistance affects the pitch and volume) The triggers i found are not voltage triggers, like standard CV stuff from the 70s and 80s. You only need to make a connection between 2 points.

    What i’m eventually going to do is wire up trigger jacks to each of the drums, and use one of these midi kits from highly liquid.
    This thing would kick so much ass with all the mods i found PLUS midi! =]

  • on the synsonic drum bending is it possible to make that midi like
    plug into midi. can i plug it into my computer to record it?

  • no.
    that’s the first thing i thought when i saw it too. But unfortunately, the synsonics has no midi.
    For some reason, they decided to use a 5pin DIN connector… It’s for the synsonics “accessory” pedals- bass drum, hi-hat pedals, etc. I know the temptation to plug a midi cable in there is overwhelming, but i wouldnt’ try it, 2 of those pins output voltage which might damage your computer.

  • i set up my synsonics so that it can be triggered by my roland tr-505, which is nice because the 505 can save rhythm patterns. to do this, first you’ll need to locate trigger outs on the 505. take an 1/8 jack and connect to ground. connect the hot tab to the corresponding resistor:
    R80- BASS
    R75- SNARE
    R2- CLAP/RIM
    R63- HIHATS
    R60- TOMS

    the trigger ins on the synsonics are located at the resistors where the drum pads are fed into the IC, four resistors right near the middle of the board.

    i was inspired to experiment with this after seeing david wright’s (carrionsound) 505 trigger a hammond analog drum machine

  • NICE!
    thanks for contributing that! I’ll definitely have to try this. A while back, i was toying with the idea of recasing the synsonics with a midi drum machine to make a frankenstein analog/digital hybrid circuit bent nightmare. Now i know it can be done easily! That’s great, cuz the 505 really needs some low-end punch.

    I also have a roland tr-77 (not 707), which is basically a preset-only 808. I gotta find the trigger outs on that baby….

  • did you ever figure out how to mod the tr 77? i bought one about two years ago for 7 dollars at the swapmeet. i’ve always wondered if it was possible to mod it so i could control ALL the sounds, anyways. i’m glad to see i’m not the only one with one of these white elephants sitting around my home…j…

  • wow, nice find. i think i paid $30 for my tr77. No, i haven’t opened it up yet, but Scott from 3 comments ago says he found the trigger inputs on a rhythm master drum box, which is pretty much the same technology as the tr77. I’ll quote him:

    i set up the trigger outs on my 505 to send pulses to vactrols i had implanted in various toys. the piezo drum pads are just creating a small pulse that triggers the drum sounds in the synsonics, so i figured that pulse could come from another source and do the same thing. i located the points on the synsonics board where the piezos were fed into an ic. i connected those points with the trigger outs from the 505 and it worked beautifully. for the Rhythm Master i just tested the 505 trigger outs at various resistors near the oscillator trim pots until i found the right trigger points.
    happy probing
  • right on .. thanks.
    would you be willing to tell where those trigger outs are on the 505? i WAS gonna bend it, but now that you’ve told me this i’m gonna make a frankenmutant drum machine thing. is it o.k to just poke around in the tr 77, and do i just turn it on wothout starting the clock?

  • read scott’s comment above. He lists the trigger out points on the 505. I haven’t messed around with them yet. I would be very careful with the tr77, since it gets plugged into the wall. That means there are some dangerous currents hiding in there. I wouldn’t poke around unless you have a very good idea of what you’re poking. I’m going to stick with the resistors near the trim pots. I might even wire them up to a patch bay when the tr77 is turned off, and then mess with that.
    Scott said he used the trigger outs on his 505 to find the trigger ins on the rhythm master. But you need to be careful with this too, since trigger outs are voltage, and you might fry something if you send voltage where it shouldn’t go.
    So, to sum up: Voltage and current can kill you or your gear, so be careful! =]

  • i just bought some Pulse Red Hot triggers for my acoustic drums. these triggers can be plugged into the trigger ins i added to my synsonics. now i can trigger all of the synsonics sounds while playing my regular drum kit. pretty rad

  • very cool. i was just looking at some of those triggers on ebay. You should try building the synsonics hihat pedal, if you can decipher the ACC jack pinout diagram above….
    I also found this simple audio-to-trigger schematic:

  • let me start off by saying thanks. thanks for taking the time not only to figure out all this shit but to post it on the web and share your information.
    now i have a quick Question, you say you didnt get to far into experimenting with the acc. jack, ( which i allready plugged my midi controller into, but nothing bad happened )
    i either want to hunt down the accessories that mattel made for this or make one, now when you said “A better idea would be to make a custom cable with a male DIN connector on one end, and female 1/4 jacks on the other, so you can plug in standard drum trigger pedals” could you perhaps go a little further into that, i think i understood what you meant, but if you dont mind gimme the “custom cable for dummies version” haha
    thanks again man you rock, when i finish my midi enabled 1 space rackmount sk-1 project ill send you pictures ..
    - Goulet

  • Hmm… Now that i look at that diagram of the DIN jack above, i realize it’s not clear whether the trigger inputs are voltage triggers or not. If they ARE voltage triggers, then my idea about the custom cable is not as simple as i thought. But i saw a picture of the synsonics ACC pedal, and it looked just like a normal guitarist’s A/B pedal with 2 stompbox switches. Unless it’s battery powered, it’s probably not a voltage trigger. I haven’t tried making a cable yet, but i’ll explain what i was thinking:

    I’m assuming that the open/close hi hat trigger is just 2 points that, when connected, let the closed hi hat sound play, and when open, let the open hi hat sound play. It does the same thing as the accent button. So you would just need to wire up a footswitch that connects to pin2 and pin3 of the ACC jack. Roland and other companies make footswitches for midi drum modules that work like this. They usually have a stereo or mono 1/4″ jack on the end. So if you wired up a female 1/4″ cable to pin2 and 3 of the synsonics ACC jack, you could plug in one of these standard hi-hat pedals. Same for the bass drum, but you’d use pin1 and pin3. You could ignore the other pins if all you want is bass and hi-hat pedals.

    I’ll have to look at the service manual and find out more. It would be nice to find the sync trigger INPUT, and make a circuit that could convert a midi clock into the required “16 pulses per quarter-note” that the synsonics needs. But i have a few other projects on the workbench right now. If anyone is interested in looking into this, let me know and i can scan the service manual….

  • Justin you may be interested to know that ive succesfully made a working accessory jack pedal. They are NOT Voltage triggers, simply completing the circuit by connecting leads 1 and 3 ( for bass drum hit ) and leads 2 and 3 ( for Hi-Hat closed position ) will do the trick! You can easily use any guitar foot switch A/B pedal, i happened to have an old Digitech FS300 A/B/C foot switch i saved when the A pot broke ( i new id eventually use the casing for something like this) as i only need 2 switches for this the missing A poses no problem. Still having switches B and C is perfect- one for bass drum and one for hi-hat close. This was actually extremely easy to do it only took 15 minutes. It would have taken longer to find which leads were which but thanks to your daigram, it was a cinch. And the coolest part about this pedal is that the Bass drum button on the Sysonics plays a steady beat and its hard to dictate a specific rythmic pattern. But with the pedal every time you step on the Bass drum trigger it Hits!
    So Weve establised that the acc Jack (5 pin din) layout is 1 – 2 – 3 – 4 – 5 in that same fashion Midi cables or female ports (for midi) are 1 – 4 – 2 – 5 – 3 to the acc jacks’ 1 – 2 – 3 – 4 – 5 , also to this same layout a midi wires color coding is yellow – black – bare wire (unsheathed) – red- white. If you were to plug a midi wire into the acc jack and cut it in half and expose the wires connecting yellow with the bare wire will give you a Bass drum hit, and connecting Black with the bare wire will close the hi-hat. once you have opened up a pedal (lets say a A/B pedal with 2 stompbox switches) rip out all the wires from the leads and start fresh. After you’ve cut your half disected midi cable to desired length, connect or solder the bare wire to switch 1-Right. (Instead of calling them A and B lets now call the switches 1 and 2. Switch 1 will be the Bass drum and Switch 2 Hi-Hat close) Now from that same connection 1-Right connect a wire to switch 2-Right. This is the common lead (pin 3 on acc jack = 2 for midi specs) Connect 2-Left to The Black Midi Wire. Connect 1-Left to the yellow midi wire and wallah! ! you’ve now got a foot pedal that fits the acc jack of your synsonic drums, you can now trigger the Bass drum or Hi-hat close by stomping on one of two switches! ! I left Red and White in the pedal just in case you guys figure out some way of utilizing the sync trigger pulse output and the bass trigger pulse output. I gave the extended instructions for everyone. Im sure you guys would figure it out in 30 seconds anyway.

  • ah, very cool! I’ve had the idea for a while, but you’re the first person i’ve seen actually do it. That’s great that now the bass drum can be played like a drum, instead of just acting as a metronome. I’m not sure what you mean by this:

      the acc Jack (5 pin din) layout is 1 – 2 – 3 – 4 – 5 in that same fashion Midi cables or female ports (for midi) are 1 – 4 – 2 – 5 – 3 to the acc jacks- 1 – 2 – 3 – 4 – 5

    But it looks like you followed that diagram, so it’s good to know it’s accurate!

    As far as the trigger outputs: The bass trigger could be used to trigger another drum machine that has trigger inputs. So every time you hit the bass drum on the synsonics, one drum on the other machine would sound at the same time. The sync trigger out MIGHT be able to sync another synsonics. The thing about CV (control voltages), is that every manufacturer has their own standards. Roland/Boss, for example, uses 12 pulses per quarter note (i think), but other companies use 24ppqn. If the above diagram is correct, the synsonics uses 16ppqn, so you’d have to figure out how to make some kind of conversion circuit in order to sync it properly. That’s another project on my list (but it’s a long list).

    [EDIT] Ok, i see what you mean about the different pin numbering. MIDI pins are usually labeled like this:

    so, just ignore that numbering system for the synsonics.

  • Hi there,
    And thanks for all the usefull infos on the synsonics drums
    cause I found one at a yard sale for 3 euros with an ac adptator last month
    and liked it immediately.
    I added a switch for the accent so i don’t have to keep the button pushed.
    And then i found your page about the synsonics.
    As you say, all the mods/bends won’t hold on the case
    so idecided to keep the original case and add a external box
    with controls over each sound:
    trigger in, sustain pot, click volume pot, tone/noise volume pot, and output
    and if i figure out the decay thing you are talking about i’ll add some other pots/switches on it.
    I think i’ll do the connection with a D-sub 37pins
    Maybe without any cable, just panel mounted connectors on the two units (the synsonics and the box) arranged so they can be hold together by pluging the one connector in the other (I don’t know if i’m understandable, in fact i’m french).
    My idea is that when the two units aren’t plugged together the synsonics
    functions normally cause i’d like to use it raw, for my drummer to keep it close to his acoustic drums.

    So i’m starting to make a list of all the connections i need to figure how many pins i need on the d-sub cable
    37pins should be enough to allow late additions like bends or other stuff i might find.
    But i have several problems/questions that maybe you can help me solve.
    First thing is about the outputs:
    I need one output for each sound (tom 1&2, snare, hithat)
    but there are two resistors for each sound (except the hithat)
    So how do i wire the output for those two sounds together ?? (click + tone, click + noise).
    The second thing is about the trigger in:
    I want to use the cable connector of the pads, This is 4 pins for the 4 sounds and 4 ground pins.
    If i wire jacks inputs directly to this can it be triggered by a tr-707 for example ? With the individual outputs of each sound ?
    In fact i don’t really know how triggers works so sorry for the lame questions.
    Another questions about the volume pots:
    If i want to add a volume pot, do i need to clip the resistors ?
    I think that if i don’t clip the resistors out i won’t get a real zero volume, just a louder volume (with less resistance in the pot than in the resistor)
    So my guess is that i need to clip out the resistors.
    but the problem is that when my box is unplugged the circuit at those places will be cut.
    So i need a switch that restores the link (with the resistors on this link)
    a switch for 7 connections at a time, i don’t know if that exists, i though of a dip switch of 7 maybe…
    And the bass drum (the metronome) maybe i’ll get it on my box with a trigger in and an output, but is it interesting ?
    what i hear is mostly click, but mabe my hi-fi isn’t hi-fi enough to give me the perhaps really low tone.
    So i wonder… but that would be great to tune it so i could really get 2 toms and one kick.
    But where to wire the trigger ? Use the acc din connexions on the board ?
    But if it isn’t CV trigger can i trigger it with a 707 like the others ???
    I can answer to that yet but i’ll search it through.
    well that’s all for now, i’ll keep you informed of my progression and will send photos as soon as this project starts physicaly.
    sorry for the long post

  • Vincent-
    wow, great questions! I’m not sure i can answer them all, but maybe we can figure them out together….

      “I need one output for each sound (tom 1&2, snare, hithat) but there are two resistors for each sound (except the hithat) So how do i wire the output for those two sounds together ??”

    I haven’t tried yet, but i think you can just wire the two resistors to the same output jack to mix both sounds together.

      “The second thing is about the trigger in: If i wire jacks inputs directly to this can it be triggered by a tr-707 for example ? With the individual outputs of each sound ?”

    There are 2 kinds of triggers (that i know of). The standard type is CV (control voltage), and is used in pre-midi drum machines. A short pulse, usually +5V, is used. The other kind of trigger is a “button” trigger- it simpy connects two points, like a button does. Maybe it shouldn’t be called a “trigger,” but i call it that. =] If you want to use a 707′s individual outputs to trigger the synsonics, i think you will have to build a circuit like the one i posted above, that will convert an audio sound into a trigger. However, the 707 has it’s own internal triggers, and it’s possible to tap those triggers to control external stuff. I don’t have the info for this, but you might find it in the TR-707 yahoo group

      “If i want to add a volume pot, do i need to clip the resistors ?”

    I’m not sure. I remember a lot of the mods i found involved clippning resistors, so i haven’t done them yet because, like you, i wanted my synsonics to be able to go back to “normal.” What i will eventually do is recase the whole thing, and use switches to switch back to normal. Experiment with pots on the resistors. It MIGHT be possible to wire them in parallel with the existing resistors, but maybe not. Another solution would be to use jacks for the volumes, instead of a D-sub. The kind of jacks that have a connection that is normally closed, but opens when you plug in a jack (like a headphone jack on a radio).

    Good luck, and let us know what you find out!

  • Thanks for the answers,
    I’ll try out when i receive my bending stuff ( jacks, box, pots, etc…)
    For the triggering stuff i’ll try what Scott Campbell said about the 505 trig outs
    For the outputs maybe i’ll add a diode between the resistors and the jack pin.
    And the volume i’ll try clipping the resistors and tell you

    I found a sustain for the hithat and the snare by connecting their corresponding out pins on the chip to the ground with a pot between
    this trick isn’t really interesting for the toms, the volume pot wiil do the same
    by wiring the third lug of the pot to the “C” points corresponding you can add more noise into the snare for example.
    The schematic is really helpfull to figure out those things
    i’ll post a link to it in my next post for everyone to get their brain on it ! !

  • thanks for posting all of this info. i finally found a syn at a flea market a few hours ago for $15 and i’m about to mod it. just found you, then this link for the service manual so i thought i would share.


  • ok freak accident here and I need help
    I was bending my synsonic and was attempting to change the kik drum sound from the origional to somthing with more tone so i was hardwiring my kik pedal to ah and c2, I had ah done and i was holding the bare end in my hand when one of the batteries exploded ! ! I dropped everything I thoght somthing was shorting out on the other side so i picked up the board to see what was going on and I guess the bare end that was in my hand fell onto that round thing the thing that says tdk on on it, it’s on the top left when the circit board’s upside down. now nothing works no lights no sounds nothing only a pop in the headphones when I turn it on. I have a show tomorrow and If I do’t get this fixed tonight I’m screwwed, does anyone know what happend? and how I can fix it or is the whole thing destroyed??

  • ok thanks para for the manual, what I hit was the transformer, what would ah to the transformer do? sounds like it fried the whole thing, I hope not , what should I do?

  • Wow, that’s the first time i’ve heard of exploding batteries while bending. Were they old? I hope you were wearing your goggles or glasses!

    The transformer handles the power. Point AH on my diagram is part of chip U3 in the service manual, the sound generator IC. So one of those 2 things is most likely damaged. What probably happened was power was sent to the IC when your wire hit the transformer. Or it could be possible that the transformer overloaded and burnt itself out, or a neighboring diode or something. If it’s the transformer or a diode, you can most likely replace it, if you can find the same one from an electronics place like Mouser.com. You might have a harder time finding the sound generator IC, i don’t know.

    This is the classic example of how things get fried- a stray wire accidentally brushes up against part of the power regulator area, and voltage get’s sent somewhere it shouldn’t. We’ve all done it before. Sometimes we’re lucky and can repalce a diode, and the thing comes back to life. Other times, the problem is harder to find, and we just give up, buy a new one, and move on. Sorry to hear about your loss. Good luck!

  • Hey guys
    i lost my synsonic tonite
    and i now understand trvor’s feelings
    i shorted the the lugs of the ic where the snare and tom2 pads are fed with the positive lug of C38, the upper right capacitor
    symptom is an everlasting noise of snare and an everlasting tone of tom2
    i’m so sad
    this is real pain
    wht do you think ??
    i must have burned up the sound generator chip
    by the way trevor if you can’t resurect you synsonics
    it would be a incredibly generous act to lend ,give or sell me you sound generator chip
    maybe i can fix mine with it!!

    let’s burn a encense for the rest of his soul
    dear synsonics

  • Okay, I’ll soon get another synsonics and be careful with it
    Here is the idea
    Recase the board in a tr-707style shaped box
    Controls over volumes and decay and more
    the little buttons to trigger the sounds at a certain rythm
    i love them and i want to pt them on the box with bir square red buttons, something nicer than those rubber thingy.
    and a 505 trigger interface (in a midi port)
    a better ac adaptator input
    maybe seprate outputs
    i feel like i don’t need those pads anymore
    the final thing will look like a classic drum machine with 4 sounds
    and controls over each sound
    i need to find more mods,
    it would be grreat to find a good distortion and a pitch for the other tom
    well i’ll keep you in touch with this project
    it’ll be nice and clean, with a fat sound :D

  • Sad that another synsonics was fried. I guess i’ve been lucky so far. Thanks Vincent and Trevor for mentioning the areas you think were dangerous, others can learn from that. It might be worth it to probe around the board with a Voltmeter to find the areas with harmful voltage.

    Vincent- that’s the spirit, don’t give up! Sounds like you’ve made some progress already. Now go and buy TWO synsonics and recase them together! =]

    I like your ideas. You’re right that you don’t need the pads. I like the pads. But if the sounds can be triggered by midi, you can use any drum pads you want. Heck, you could even hook the synsonics pads to a midi drum brain and make midi triggers out of them.

    I’m pretty sure i found the pitch for the other tom on my synsonics mods page

    Other things that need to be acomplished:
    -Find a way to sync the synsonic’s clock to midi
    -Reduce the hum in the output

  • In fact the thing that i have in mind for some weeks now is a
    midi input
    i think it’s clearly possible
    there is highly liquid who is doing a good job with his midi kits
    and i wonder if it can be adapted to a synsonics
    an then it would become really complete
    this is my ultimate goal
    but it’s september and the school started again so the time for probing will dicrease to near zero
    but this project need researches on midi and electronic
    as you said in the tr-505 post if i remember well, bending starts with no knowledge at all and gives you the need to get more
    this is so interesting
    So keep on the good work everyone !!!
    If we all focus on a machine we will build a real encyclopedia of bending !!

  • Exactly! An “encyclopedia of bending” is what we’re moving towards at this website. Since we adopted the blog format, visitors have been able to contribute their own info thru the comments. I think we may start a forum area where the discussions can be organized in an easier way. And visitors can actually start topics. Stay tuned for that. =]

    Yes, the highly liquid kits are perfect for this type of project. Thom and i have each started building MSA kits as stand-alone midi-sync boxes, and wiring trigger jacks to all our gear. But you can just as easily build them into any project.

  • hey guys-im a donut at doing mods ie i know how to turn on a soldering iron..but i just bought a sysonics drum machine on ebay and its terribly noisy…is there some way i can fix this..also it came with out a manual..is the power input near the midi input???i live in australia so the power is bit different-works fine with batteries…awesome memory option!

  • daz- i just uploaded the synsonics service manual to our manuals and schematics page. Yes, the power input is near the DIN jack (that’s not a midi jack!). As far as i know, all synsonics are a bit noisy. There is a loud hum when you crank the volume up. I haven’t figured out how to fix this yet. I would search for “ground hum” on EFX pedal DIY sites to find a generic solution. (let us know if you find anything) If this is your first project, be very careful. If you read these comments, you’ll see that it is easy to accidentally fry the synsonics (and anything, really). Yeah, the memory bank is neat. Pretty powerful for a “toy” from the people who brought you the intellivision video game system, and the Barbie doll! =]

  • Mattel always took risks with new markets.
    Let’s not forget Mattel gave us the amazing Optigan too!

  • Hi there,
    My project to rehouse the synsonics is close
    but before i have some questions without answers maybe you can help me:
    first is the tune of the tom 2 On your mod page Justin you say that it is between AF and C5 but where is the C5 ?? i’ve searched it and also tried to find infos on the schematics, there is apparently a unused pin on the sound chip but i can’t use it like i’d want ^^ i will give up soon on the tom2 pitch i think…

    then there is the bass sync with the accessory i didn’t figure how it works… cause trigger the sounds with midi is great but to use the drum mini keys is so much fun but impossible if it isn’t synchronised with your other midi instruments !

    there is also the pan, the integratedpan is annoying and i’d like to have control over it, i’m investigating this at the moment but if you have ideas or suggestions it can be of great help !!

    I’m sure i forgot something but i’ll post again once i find what it is.

    Thnks for your answers or remarks


  • Ha i remember it was a question about mini pads
    do you know where i can find mini pads for finger play
    like the one on the mpc or more simply the sr-16 ??
    id like sensitive pads i can build them with piezo triggers also
    but i’m not sure i’m capable of something really nice
    so i you know where i can buy some or where there’s a tutorial to DIY finger pads that would be awesome

  • Hmm… i’ll have to check my notes for C5. It’s most likely in that same area.

    I haven’t experimented with the bass sync. Apparently, it is a tap-tempo. If that’s true, you should be able to trigger it with a relay-type trigger, like the highly liquid MSA kits. But I don’t know if it would be precise enough for midi sync.

    The hard-wired pan is most likely done with resistors. The audio from each drum gets routed to both L and R outputs. But before it gets there, it passes thru some resistors that make the drum louder in one channel. You should be able to replace these resistors with resistors of the same value, to make the balance even. Or you could replace them with pots; then you will have pan pots.

    Here’s a guide to making DIY drum pads. I know there are 3rd party replacement pads for the MPC too. They are rubber with conductive material on the back. They are about $25. But you should be able to use any rubber material over the piezos.

    Good luck, and you’d better send us pics!!

  • Hey justin, great site you have here….listen , the knob on the left side of the unit (pitch) for the bass i think?!?!? isnt working…what can i do to fix it?….

  • Well, it might have come loose from the board. A soldering iron can fix that. You could also replace the pot with a new one, but you might have to mount it somewhere else on the case.

  • Thanks for all the work you’ve done compiling info on the Synsonics drums! I’ve got a set that a friend is lending me and I’ve been able to fix some small problems thanks to the manual, and built the bass/accent pedals according to the info posted by goulet. I won’t get to do any bendng until I can get one of my own, but you’ve already given me more than enough to keep busy with.

  • hi i just got one of these from my freinds on 2/27/07 im 15 years old and i wanna know how to do mods to these things sum one please email the way to do at (senoraltaco-at-aol-dot-com)

  • al- all the info we have is on this site. We assume people using this info have a basic understanding of electronics or can at least use a soldering iron. There are other sites out there that have more detailed beginner info about circuit bending and modding. Check our links page for some places to get started. Good luck, señor!

  • Great site. I just picked up a synsonics drum tonight. I have a relative who use to work for Mattel back in the 80′s and he had a box with alot of old video games, in the bottom of the box was this drum machine. Way cool. Only draw back its missing the manual. Anyone know if there is a manual on the web, trying to get the record/playback to work – its not and not sure how to store patterns in memory. Thanks


  • Bill- wow, i wish i had a relative like that. =] We have the service manual here, but not the instruction manual. Does yours still have the sticker on the bottom with instructions? Here’s the text from that, which i found here:

      TO RECORD, hold down Record key while pressing 1 of 3 memory keys. Record starts 1/2 sec. after Record key is released. Duration of each memory loop is 16 beats of overall tempo. All LEDs flash at start of each loop. Memory loops can be layered indefinitely with drum pad or key play. TO STOP RECORD, press Stop key. All memories are erased when drums are turned off.

    The 3 memory slots are accessed with the 3 cymbol buttons. So you press Record and cymbol 1 at the same time, it will wait a second, then start the 16 beat loop. It helps to have the BASS drum on, it acts like a metronome.

  • I bought one of these new back in the day for about $100.00. I still have it and the manual so I will see if I can dig it up and scan it for you guys.

    The recording insturctions above should be all you need to record and playback patterns.

    One more thing, if you push two of the buttons for any given drum sound at the same time you will get triplets or other patterens. I can;t remember which pattern does what but just experiment with it.

  • So in an attempt to conquer my Synsonics’ hum problem, I finally did a thorough reading of the service manual, and down at the bottom in very small print they suggested replacing C39 & C40 with 10uf caps (1uf is what’s installed). THIS WORKED PERFECTLY. No hum at all now. Just thought I’d share. :)

  • nice! See? A buzzkill can be a good thing sometimes. Or i guess you’re more of a humkiller. I suspected that a capacitor on the output would do the trick, but it’s amazing that the service manual had the secret in it the whole time! Thanks for sharing that!

  • sorry for some simple questions:
    - how can i open this gear?
    - is it possible to repair the sensitivity of the drumpads?

    i bought one and it works, but 3 of the 4 drumpads are not sensitive anymore… must use a hammer to get a sound out of it.

  • Page 7 of the service manual describes how to dissasemble the synsonics. Page 8 has an exploded diagram (love that term).

    The drum pads are piezo discs, which can be ordered at any electronics parts supplier. I’m not sure exactly what type they are, but the service manual might have that info..

  • This sight is amazing… I’ve been going it alone for years, countless bends and many failures. I’ll be checking back, I’m firing up the soldering iron for the synsonics. Thanks!!!

  • rmosquito Says:
    May 7th, 2007 at 9:38 pm
    So in an attempt to conquer my Synsonics’ hum problem, I finally did a thorough reading of the service manual, and down at the bottom in very small print they suggested replacing C39 & C40 with 10uf caps (1uf is what’s installed). THIS WORKED PERFECTLY. No hum at all now. Just thought I’d share. :)

    I didn’t have a hum problem. What I DID have was a low-level but clearly audible “ticking” sound or clocking noise, which I erroneously attributed to insufficient (i.e., NONE) decoupling of the microcontroller and RAM supply voltage.

    The solution was to increase C23, the U5/U6 supply filter cap, to 470µF @16V. (This suggests to me it wasn’t “clocking” at all, but some battery-related phenomena.) Now I can barely hear the ticking with the Synsonic volume and my amp turned ‘way up and I put my ear to a speaker. The cap can be soldered on the component side of the board at pin 6 (+) and pin 4 (-) of either U5 or U6.

    Now, for my modifications:
    I’ve given the Cymbal variable Decay — not just open/closed — and a simple Tone switch.
    The Snare has 3 Decay settings, Tone control and increased Impact.
    Tom Tom 1 has a lowered frequency range and Tom-2 now has variable pitch. Both Toms have variable Decay and increased Impact.
    I’ve made no changes to the Bass. It still sucks.
    I’ll make details available when I have sound samples. Right now my Synsonic is in no condition to be moved close enough to my PC to record it :p

  • Could you post more details on these mods?


  • All in due time squid!
    My synsonics is next on the chop-block, so hang in there.
    Good things (& free info) come to those who wait.

    That said, RichardC64, how about you share some of those mods with the rest of the class?

  • OK, you talked me into it, even though I’m not ready to post sound samples and won’t be able to do any more work on it this week. Bear in mind, my mods are not meant to fit in the Synsonic case. I’ll be putting it in a bigger box, with larger drumpads. I suppose my mods could be made to fit with teeny-tiny switches and pots near the rear of the case, on either side of the battery holder. I wouldn’t like to try it, though.

    Oh, and the ticking sound was little more complicated to deal with than what I described above. I’ll post that only if anyone else is having the same problem.

    SNARE: At first I used a 3-position, center off switch to lengthen the decay by putting another 2.2µF cap in parallel with C9, or a 10K resistor to shorten it. The “off” position left the decay unchanged. I’ve since changed that mod to a variable decay, with a pot, resistor and capacitor.

    More Impact is added to the snare with a .01µF cap .1µF cap, resistor and switch. The The Snare Tone pot lets more of the snare noise high frequencies come through. (The shielded cable provides the ground connection for the pot.) Shielded cable is necessary, where indicated, because U4 pin 6 (and pin 2,) is an op amp summing node, which is sensitive to hum and noise pickup.

    TOM TOMs: Before describing the Tom Tom mods, I must explain that I do not intend to use them for Tom Tom sounds. I plan to use two d.i.y. circuits for those and other sounds. What I’ve done, however, leaves Tom-1 and 2 still usable as Toms.

    The Snare and Tom-1 piezos will be in the same drumpad, and can be struck independently or coupled electronically by the Link switch, with Tom-1 providing a “shell” or “rim” sound for the Snare, depending on how it’s adjusted. (This linking applies only to the drumpads, and has no effect when either Snare or Tom-1 are played via the Synsonics’s buttons or memory, neither of which I plan to use.) Tom-1′s frequency range was too high for my taste: I lowered it by putting a .1µF cap in parallel with C4. I am still seeking a way to reduce the effect of the built-in and unalterable frequency sweep of Tom-1, which is too extreme, and sounds trite. So far, no luck.

    To me, the Synsonic “Bass” is miserable, sounding more like a click than a thump or thud, and I was unable to improve it. I’ll use Tom Tom 2 for a Bass, with its pad being struck by an actual bass pedal. I made Tom-2 tunable over a limited and lowered range by adding a 1µF non-polarized cap in series with a 10K pot across C5. More resistance = less capacitance = higher pitch. (Maybe I’ll retain the Bass On/Off and Tempo buttons for a beat to practice with. That’s all it was ever good for, IMO.)

    The Decay and Impact modifications of Tom-1 and Tom-2 are nearly identical, and very similar to the Snare mods.

    In Tom-1, for example, C12 is the decay capacitor and R73 bleeds off the charge. The added 2.2µF cap and a fixed + variable resistance allow the decay time to be adjusted from shorter than originally to longer. Values shown produced results that sounded right to me. For both Toms, more Impact is added to the sound with a switch, .01µF cap and 47K resistor. Shielded cable was used here for the same reasons as in the Snare mods.

    I am not satisfied with my CYMBAL mods. I’ll post that when I *am* satisfied.

    All of this is what I’ve wanted to do since I purchased my Synsonic in the 1980s! I lacked the necessary information. None of this would’ve been possible without the Service Manual generously provided by Justin. However, I found the schematic difficult to read, so I’ve enlarged and enhanced it, (click image to enlarge)

    minus the unreadable waveform charts, which I enhanced separately, clarifying (to the best of my ability,) what I consider the important Test Points. http://www.sdiy.org/richardc64/synsonic/wave_bw.gif (click image to enlarge)

    The component layout was also tough on these old eyeballs. I enlarged that too, faded the obscuring pc traces and hi-lighted points important to my modifications. (click image to enlarge)

    Feel free to look over the rest of my website, starting here http://www.sdiy.org/richardc64/proj/

  • Wow. I’m glad i asked. Anything else you want to talk about :)?
    Seriously, thanks so much for taking the time to write that up.
    And double thanks for the documentation & fixing up those schematics.
    They are all such simple little mods, but it’s amazing what a difference they can make.
    If it’s alright by you, we’ll mirror all those gif’s here in case geocities flakes.

  • Correction: More Impact is added to the snare with a .1µF cap, resistor and switch.

    Thom Says:

    “Anything else you want to talk about :)?”

    Too long-winded? Sorry, I like to explain what I’ve done and why, because maybe someone might think up a better way or a refinement, or try something similar on a different device.

    “If it’s alright by you, we’ll mirror all those gif’s here in case geocities flakes.”

    Er…I’m not sure about the implications of that, but sure, go ahead. My schematics are subject to change, though.

    I gotta emphasize that I wouldn’t be able to do what I’ve wanted to do for so long if I hadn’t found Burnkit. Thanks so much.

  • Richard-
    Feel free to be as long-winded as you want! Please! That’s what these comments are for, after all. You say you wouldn’t be able to do what you want without us, but it’s reciprocal- We try to inspire people to get involved in these projects, and often enough we get inspired by people like you who take our ideas and run with them.

    As for your images- I hope you don’t mind, i put them on our site so that they display in your above comment (without using bandwidth from your site). If you update them or add more, you can comment here, and i’ll update them.

    Thanks for sharing!

  • Justin Said:
    “As for your images- I hope you don’t mind, i put them on our site so that they display in your above comment (without using bandwidth from your site). If you update them or add more, you can comment here, and i’ll update them.”

    Very cool! I’m honored. But won’t the larger images use too much of YOUR bandwidth every time the thread is viewed? Don’t be concerned about my bandwidth. No one goes to my site.

    The Correction needs correction. It’s in the wrong location. It belongs further down in regards to the Snare Impact, not in the paragraph about Decay.


  • Oops, Corrected the Correction…

    Yeah, we should have enough bandwidth for pics, keep ‘em coming!

  • I think your MP3 demo might be corrupted. It sounds crashed and glitchy and it only lasts for 1 second.

    Oh, or is that the circuit bends?


  • Here’s my Cymbal mods. Justin, Thom, don’t even ask. If you want to host the pic here, go right ahead.

    The Synsonic’s Cymbal isn’t much of a cymbal, but it’s good for a start and the “Accent” button/footswitch, simulating a closed Hi-Hat sound, is a nice touch. The short, “closed” decay didn’t seem short enough to me, so I put a 2.2K resistor in parallel with R32. This more rapidly discharges capacitor C6 when transistor Q2 is conducting.

    Instead of a foot switch, I thought I could use a foot pedal to apply a control voltage to the base of Q2 to get a decay between fully open and completely closed, but that hasn’t worked too well. For one thing, Q2 is configured for on-off operation and isn’t very good at “in between.” Also, because the pedal’s travel doesn’t allow full rotation of its pot, (they never do, just like Joysticks,) there isn’t much variation in either resistance or voltage, if used as a voltage source. A simple solution would be to ignore Q2, and put the pedal pot from the collector to ground, but the pedal I want to use has a 20K pot, which isn’t enough resistance to allow a fully open decay, even if I could get the full resistance range. Besides that, I don’t want to bring pin 7 of an irreplaceable chip (U3,) directly to an “outside world” potentiometer, not even through R32.

    For now, the pedal works well enough, and does feel more like a hi-hat pedal than a footswitch would, but it doesn’t have much effect until almost fully depressed. This mod still needs more work.

    The added .01µF capacitor lets more of the noise low frequencies come through. Control wasn’t subtle enough to justify using a pot, so I just used a hi/low switch. The 1Meg resistor keeps the low “pitched” cymbal from drowning out any other sounds the Synsonic is making.

    Sound samples “real soon.”

  • richard- cool, i can’t wait to try these mods out!
    squidfanny- heh, weird. I fixed that mp3…

  • It seemed to me there was too much blend and not enough separation so another thing I did was eliminate the blend between the Left and Right channels by clipping out resistors R50 and R51. Absolute separation.

    It should be possible to achieve a Blend control by inserting a dual pot, as shown. (I think someone already suggested this.) I don’t know what would be a good value (Maybe at least 20K?) or if the pot should be linear or log. Obviously, I have not tried this.

  • Yea, definitely too much blend. If you’re not going to do separate outputs for all the drums, then this is mod is the way to go. I’d probably go with linear 20k’s.


    Regarding the notation of PIN 4 on the original diagram at the top, after looking at the schematic blow-up provided by an earlier poster, it’s not clear to me that it is indeed an “output”.

    For instance, there is the bass trigger sync output on PIN 5, which makes sense that it would be an output for the internal sync generator (bass click track), whereas PIN 4 would most likely be the 16ppq SYNC INPUT. Seems like you could feed this would-be input a stream of pulses “on tape” and sync up the tempo easily for multitrack recording.

    Any thoughts?

  • well, if it turns out to be that simple, i will be kicking myself. in the butt. very hard. If that’s not physically possible, i will get someone else to help.

    I experimented a little bit last nite- I was able to trigger the bass drum by shorting pin 1 to pin 3(ground). And lo- when you turn the bass drum click track off, the bass drum trigger acts as a tap tempo! Until now, I had only tried the tap tempo function listed on the back cover instructions- tapping both tempo buttons. That never worked very well. But shorting those 2 pins works nicely! I was able to sync the synsonics to another drum machine by ear- as long as i kept hitting the 1/4 notes, it stayed in tempo!

    I didn’t have time to try pin 4. But even if pin 4 isn’t a sync input (and, it WOULD make more sense for pin 4 to be an input, rather than an output like that diagram says, right?), i think the pin 3 tap tempo could definitely be utilized with a midi trigger circuit. We’ll have to experiment some more with this!

  • If it is an input — which I doubt — it would have to be digital, since it goes directly to a cpu pin. There’s no circuitry to condition a signal from tape.

  • I just probed all the pins, and i can confirm that pins 4 and 5 do in fact, OUTPUT pulses. The diagram at the top of the page is accurate- Pin 5 outputs 1ppq, and pin 4 outputs 16ppq.

    Which still leaves us with the question- Why did Mattel include a sync output in the first place? The bass and hi-hat triggers are obviously for foot pedals (a rare accessory they did release), but why the TWO non-standard syncs? Normal DIN sync is usually 12 or 24ppq.

    Maybe they were planning on releasing an accessory that let you sync 2 synsonics together? The bass pulse output of one synsonics could concievably provide the tap tempo pulses to sync another. Those 2 pins would connect together if you hooked up a DIN cable between the 2 accessory jacks (i just tried it with a MIDI cable, no luck)

    That would explain the bass pulse output, but i wonder what they had planned for the 16ppq pulse output? The Mattel Synsonics Bassline? OOh, that would have been sweet!!! =]

  • Justin Said:

    “…why the TWO non-standard syncs? Normal DIN sync is usually 12 or 24ppq.”

    I think they just didn’t know any better.

    “Maybe they were planning on releasing an accessory that let you sync 2 synsonics together?”

    Actually, those lines can be bi-directional, defaulting to output on power-up. There could be some button combination that would establish one Synsonic as “slave.” Seems kinda pointless, though. The only sound that could be varied between two sync’ed (non-bent) units is the pitch of Tom-1. The other 3 sounds, being doubled, would have a degree of “phatness” but that hardly seems worth the trouble. Maybe it was planned to somehow interface with their ill-fated Aquarius computer.

    Or maybe they had no firm plans at all, and just made those signals available for when they might come up with something in the future.

    “The Mattel Synsonics Bassline? OOh, that would have been sweet!!! =]”

    It’s fun to speculate on “what might have been.” It’s also depressing.

  • Ok, i tried synching the synsonics with midi, using the tap tempo i mentioned in comment 66 above. It KINDA works. Not very well. I’m using a midi sequencer and a Highly Liquid MSA kit to short pins 3 and 1 on quarter notes. It seems to work ok at some tempos, but not very well at other tempos. So it’s back to the drawing board, i guess. There must be some way to tap into the internal clock….

    Off topic- i just noticed that while my normal synsonics’ memory is wiped clean after a power-off, my “synsonics stereo pro” (has 2 built-in speakers and a “cassette in” jack) remembers the programmed sequences even after a power-off. I guess that’s what makes it “PRO.”

  • Finally, samples! Nothing dramatic or really out there, just more control over the sounds.

    But first, two changes: The added Snare decay capacitor is now 4.7µF.

    Also, I found I needed more volume from Tom-2. I put a 470K resistor in parallel with R42, creating a total resistance of approx. 150K.

    All resistor and capacitor values in my modifications should be considered as starting values. You might find different values better suit your ears.

    While recording the following samples I noticed the mods did not sound quite the same through my PC speakers as they did through my stereo system, on which I worked them out. Most noticeably weak was the effect of the Impact switches. Adjust your bass and treble controls, if your PC spearkers have them. And be careful with the volume for the Toms!

    Each sample begins with 8 beats of more or less unmodified sound, followed by knob twiddling and switch flipping as noted.

    Snare: long to short decay, low to high tone, then more Impact added. (Barely audible.)

    Tom-1: medium pitch and decay, then (new) lowest pitch, longest decay, shortest decay, then more Impact. Note that when any drum has its shortest decay, the sound is pretty much ALL impact. One way to minimize the pitch sweep of Tom-1 is to select a low frequency and short decay.

    Tom-2: pretty much the same as Tom-1 but with a lower frequency range and less severe pitch sweep. This will be my Bass drum.

    Snare and Tom-1 combined at various settings.

    Cymbal: open decay, adding low tones, then depressing the pedal. I can get only three distinct decays — open, short and really short.

    I have found a few other ways to vary the Cymbal sound, but I’m going to leave this mod as is for now. Eventually I’ll separate the Cymbal output and run it through some kind of filter, probably a simple bandpass.

    Thom Said:
    They are all such simple little mods…

    Yeah, well, they’re simple electronically and schematically, but when actually performed…

  • Wow, the short decay tom2 and the tom1/snare are very 808 sounding!
    I remember there was a way to mix noise in with the toms, also. With a short decay, you can turn a tom into a snare.

  • Great samples! your instrument panels look pretty nice too. no one has to know that they’re hiding that rats’ nest. Have you thought much about a breakout box yet? what kind of design are you going with?

  • Thanks guys. Thom, those panels are meant to be a temporary convenience while I work things out. The material is some sort of super compressed cardboard or something. I could have written on them in pencil but I figured printed labeling would give me a better idea of what I’d need to do on the “final” paneling. Apparently, neat printing makes all the difference in appearance. Mediocre photography helps, too :-p

    I’m relieved that the samples sound ok. Since the sounds changed slightly in going from my stereo to my PC, I was concerned that putting them on the ‘net might mysteriously introduce yet another change.

    Thom said: what kind of design are you going with?

    Ugh. I have in mind a box with a sloped front for the control panel and a slightly sloped top for the playing surface. I say “ugh” because I haven’t figured out an exact design that’s compatible with my limited woodworking skills. All I have so far is the “playing surface.”

    The top left pad will be the Synsonics Cymbal/Hi-Hat. The bottom left pad has two piezos for Snare and Tom-1. Tom-2, which will be my Bass, will have a pad struck by a pedal. The remaining pads will get d.i.y. drum synth circuits. More info was posted here:

  • Richard on electro-music:

    Most of the materials in the photos were “found”: the piezos were the “tweeters” in discarded boom-box speakers; all the wood used and to-be-used was found; the star field wall covering, floor pad and Winnie the Pooh mat were found. The mousepad and foam rubber were purchased at Canal Rubber Supply, Canal Street, NYC.

    Awesome! That’s the way to do it, man!

    What kind of ideas do you have for the custom drum circuit?
    There are some good links in this post on electro-music.
    This one blows my fraking mind.

  • There are good links all over electro-music.

    I will be using two Thomas Henry UD-1 drum synths for 2 of the pads. Info is available here. http://mypeoplepc.com/members/scottnoanh/birthofasynth/id23.html I traded something of mine for 2 blank pc boards and the hard-to-find ICs.

    A similar design is
    http://m.bareille.free.fr/ds7clone/ds7.htm (also the ds8). It has some advantages over the UD-1. It is single-supply, includes an LFO, and of the ICs it uses only one is discontinued, but not impossible to find. Check out the samples at the bareille site. A sticky post at electro-music includes a strip-board redesign dual version with a somewhat easier to find IC.

    I haven’t decided what to use for my other 2 pads. I need another cymbal and a multi-purpose circuit. I might come up with something of my own using ideas “borrowed” from other designs.

    In an email, The Electronic Peasant has admitted that his drum synthesizer was a little too elaborate and ambitious, and he has put it on the back-burner. For now he is using acoustic drums — something I cannot do living in an apartment.

  • richardc64, I am totally awed; what you’ve done is incredible.

    Justin, you mention upthread that you were planning to try triggering the individual pads using a Highly Liquid kit. Did that ever work out?

  • Richard- cool, i can’t wait to see what you end up with. I’d like to try my hand at building some custom analog drum circuits soon. I also have a DR-110 that is in serious need of some mods!

    Ben- I haven’t tried the Highly Liquid kit yet, but i think Thom may be attempting that soon. The MSA-T in particular- I’m 99.99999% sure it will work. We’ll post details when we get there.

    In the meantime, if you decide to order a kit, send an email to John at Highly Liquid and tell him what you’re planning to do. He’s a nice guy and will probably offer some pointers.

  • I found this pad awile ago, couldnt find a ac for power and didnt wanna buy batteries anyhow you all have inspired bme. I search and found a power source but the damm thing wont make any noise. Have you all figure out midi ye? that would be ideal if we could use this as a midi controller in reason. Im going to open her up and clean er. hopefully she will power up.

  • You really should buy batteries. Spending a couple of bucks could save you a lot headaches.

    An AC adaptor should put out 9 volts DC with positve at the tip of the plug. The reverse won’t hart the Synsonic, it just won’t work — which why you should try batteries first.

  • Hi, firstly I want to thank Richard64 for all the synsonics mod’s.

    Combined with a 505, the synsonics now sounds really good. I do have a question though…
    I’m having a little difficulty with the TOM 2 tune mod. I am using a 10k pot, and a 1.0uf cap (big red ‘non-polarised’ one), and connecting to the non-grounded pin of C5. Pin 1 of the pot is connected to ground, pin 3 goes through the cap and then to C5, and pin 2 of the pot is connected to pin 3…… Am I doing this correctly? I’m thinking that I’ve either mis-read the diagram or brought the wrong kind of cap, right?
    Ok, well thanks again for all the ace work on this machine…….:-)

  • Squid, you haven’t said what the Tom-2 mod is or isn’t doing, but your description sounds correct. One “outer” terminal of the pot connects to ground, the center terminal and the other outer pin connect together to the cap, and the other end of the cap connects to the non-grounded pin of C5. Check that you have the right lead of C5. Should be the same as pin 22 of U3.

    The frequency control isn’t very subtle. You might find turning the pot causes the pitch to jump from normal to some lower pitch, with nothing in between, or the Tom-2 VCO might stall, and stop oscillating altogether. (I’ve had that happen with Tom-1.)

    If your wiring is correct, try different value caps, say a 0.47uf alone or in parallel with the 1uf. Then again, the cap I used was blue, so maybe you just used the wrong color :-p

  • Thanks Richard64, the problem was a dead cap! Worked fine with the 0.47uf, so I tried another 1uf and surprise – it works. I suppose it was obvious really… I’ll know for next time to check the component before hassling the pro’s!

    Thanks again for sharing all this info, it’s really appreciated.

  • Hello again.

    A few posts back I expressed dissatisfaction with the severity of the pitch sweep of Tom Tom 1. (I called it “trite.”) I’ve found a way to vary the depth of sweep.

    (Thom and Justin, if you want to host the gif here, go right ahead.)

    In addition to the .1µF cap I added to lower the overall range of Tom-1, I added another .1µF cap to a diode to ground. When a voltage is applied to the diode anode it varies the diode’s dynamic impedance, forming a crude voltage-controlled resistor. Another diode takes the Tom-1 “envelope” from TP33 (U3, pin 5) and through a pot and 47K resistor that voltage controls “how much” of the .1µF is present. (The action is similar to the cap and pot I added to vary the pitch of Tom-2.) The effect is, while U3′s internal workings are sending the pitch of Tom-1 up and then down, the Tom-1 envelope sends the pitch down then up. With the pot at “min” (which should be fully CW) the sweep is almost completely canceled. Ideally, there should be more down/up than up/down, so that centering the pot results in zero sweep and sweep can go in either direction, but I couldn’t make that happen.

    I recommend that TP-33 be obtained at the U3 end of resistor R72, rather than at the IC pin. See my enhanced Component Layout pic above.

    For anyone interested in the box I’m building to house all this stuff, some info is here:

  • Arrgh. Maximum voltage produces minimum sweep, and that should be at the pot set FULLY CCW.


  • hi richard. just started doing the first portion of the snare mod (attack/decay) with little success. it seems when i have the 4.7uf cap, the 2.2k resistor, and the pot all connected to the 2.2u cap(#9), the only output i get is the white noise generator for the snare on continuously. i can adjust the gain of the white noise using the added pot, but that is all. any ideas?

    thanks again for posting these mods, btw. i love this little pad.


  • nevermind! my ground was incorrect to the board and it was triggering a continuous white noise via the snare.

    regardless, i was wondering if you (richard) would be interested in elaborating on your elimination/near-elimination of the ticking noise. i’m also having a tough time getting rid of an incredible amount of hiss. any suggestions?


  • First thing Bill, thank you for NOT writing “irregardless.” Did you have this incredible hiss before starting the Snare mods? If not, it sounds like you’re still getting continuous snare noise. Do you have ground at the “Tone” pot?

    As for the “ticking” sound, if you’ve listened to my samples you’ve heard that it’s still present. I wish I had another, un-modified Synsonic to experiment on. Thinking the problem might be battery-related, I tried several seemingly suitable wall warts. Each caused such horrendous HUM that I built an AC supply with an LM7808 regulator. (Good enough. Six fresh batteries will drop to less than 8 volts as soon as ANY current is drawn.) This didn’t reduce the ticking, though.

    The enlarged schematic I posted ‘way up there ^ shows some of the things I tried, with the notation “Add”: increased filter caps at +9V to the LM386s, U5 & U6; more capacitance on -9V at C37 in the DC-to-DC converter; and a big cap on Vcc1, where 9V from the batteries or AC adapter enters the unit. All these things helped, but only a little. Start with 100uF and work up to 470uF.

    It was suggested to me that the ticking originates in the DC-to-DC converter where, according to the manual, Zener diode VR1 shuts down the converter when the -9V line exceeds 10 volts — that is, periodically!

    Since more filtering on -9V hadn’t seemed to help much, I decided to do something drastic, and I honestly CAN’T recommend this to everyone. I supplied +5V to the microprocessor and RAM from a 7805 connected to Vcc1, removing that load from the DC-to-DC converter. This resulted in the greatest reduction — but unfortunately not total elimination — of the ticking.


    On another forum, I was criticized and my judgment questioned for doing this because it quote eliminates the isolation unquote. To which I respond: WHAT isolation? Ground is ground is ground and common on both sides of the transformer. Furthermore, the non-converted, raw DC Vcc1 that powers the DC-to-DC converter also powers the output amplifiers, so WHERE’S the isolation?

    Anywho, how I did this is shown below. A lower current 78L05, which comes in a smaller, transistor-like package, will be easier to fit on the circuit board than the 1Amp 7805 I used. Tack-solder the center leg to the triangular shaped ground trace and run wires to the In and Out legs. Since the 1N914 diode D26 that originally supplied 5 volts can carry only 75mA, the 100mA capability of a 78L05 will be sufficient.


    Again I stress that this mod is not for everyone. If you have the slightest doubt in your ability to do this, then DON’T.

    If nothing else, I’ve made the current formerly powering the micro and RAM available for powering the d.i.y. stuff I plan to attach to +/- 9V. If the ticking becomes unbearable, I might have to abandon battery operation and build a bipolar power supply.

  • this is great!

    i have not added the “tone” mod to my pad yet as i am waiting for some components to come in the mail (i live on a very small island where i cannot go to the local electronics store). it seems as though the hiss did reach an increase in gain after i performed the decay mod on the snare, though it did have a slight hiss before. the pot i used for that is grounded and even when i disconnect my circuit entirely, the hiss is still present.

    as far as the ticking goes, i added the cap at U6 pins 4 and 6 and i also replaced the 1uf caps at c39 and c40 which i believe was a suggestion by someone else. this seemed to help a little, though i have not tried adjusting c37 and will try that next. i will check your modified schematic. the +5v from a 7805 seems interesting and i will also look at that schematic.

    i will keep you updated on my progress. hopefully my components come soon!

  • i have now added the 78L05 (which i had a couple of) to the board replacing d26. originally, i clipped d25 (whoops!), but fortunately i had a few extra 1n914′s and was able to replace d25 with a new one. i also added the 1000uf cap at c38. both of these seemed to reduce the “ticking” greatly and i am pretty confident that if i can figure out my “hiss” problem, it will greatly decrease the obviousness of the clocking noise.

    richard, thanks again for all of your help. if you have any more clues to solve/reduce the hiss problem, i would be very interested in your advice.


  • Bill, I don’t have a hiss problem, so any clues I might provide would be purely theoretical. One suggestion I can make is to not do any more mods until you cure or reduce the hiss to your satisfaction.

    A certain amount of hiss is inherent to the circuit. The dual op-amp U4 (RC4558, MC1458, etc.) is not a low-noise IC by today’s standards. The LM386s are bound to add some noise as well. But any background hiss should not normally be noticeable at normal listening levels. Capacitors C16 and C24 at U4 are suppose to limit the high frequencies and thus reduce any hiss. C18 and C26 at U5 and U6 do the same thing. Is your hiss on both channels or only one?

    Measure the voltages at TP26 and 28, the Cymbal and Snare pulse pins. With no pads being struck or buttons pushed they should be zero volts or close to it. Any significant voltage will enable the noise used for Cymbal or Snare. Maybe Q3 or Q4 are somehow leaking noise from the noise IC, U7?

    If you have or can borrow a ‘scope check backwards from the outputs to find where the hiss occurs. No ‘scope? Make an audio probe consisting of a .01uF cap in series with 100K (or more) to an amplifier and use that to signal trace. Use shielded cable and be careful with the volume level!

    U4 can be replaced with a TLO72, a low-noise JFET dual op-amp — BUT replacing any IC or transistors Q3-4 is a step I’d classify as “drastic.” Look for bad or leaky caps first.

    Good luck and ffs be careful!

  • wish i had a scope…

    i had not planned on venturing further until i find some clue as to the origin of the “hiss” issue.

    i will check the caps you suggested, but replacing u4 might be a bit drastic and i don’t think i want to have my guard raised even further on my pad. the audio probe is a fantastic idea, though. i had not thought of that and will probably give it a try. i can always use a limiter in the long run.


  • breakthrough:

    i found that if i grounded a side of the “tone” pot to the snare, the hiss is decreased dramatically. i guess i should have grounded it anyway seeing that there is no ground to start for it…duh.

    thanks for all of your wisdom and great suggestions, richard.


  • Richard64, using a diode as a voltage-controlled resistor???

    Wow, I didn’t know you could do THAT…

    Anyhoo, I’ve added seperate outputs and volume pots to my mutant synsonics/tr-505, and it seems to have solved the hiss/clicking problem. Now I need to build some amps and filters ‘cus it’s very quiet, but the main problem of hiss and clicks has been cured.

    I know it’s a bit of a drastic soloution, but I needed to learn a bit about op-amps and filters anyway.

  • It’s very crude, and only works in circumstances where one lead of a capacitor (or in some cases a resistor,) would normally connect to ground, such as simple filters (“tone control”) or very simple oscillators.

    I’ve found that keeping whatever cap a particular circuit originally had, and adding a second cap with a diode “VCR”, seems to work best. The control voltage can only increase the capacitance.

    Glad you’ve solved your click problem, Squid. I’ve thought of something else that might further reduce mine, but I won’t be able to try it for a while.

  • Where is the Japanese site you got those diagrams from?

  • I found them years ago. I don’t think the site is around anymore. At the time, it was just about the only synsonics info on the web.

  • Hi. I stumbled upon another way to modify the Synsonic:

    Jyoti at moogmusic.com forum

    “Ummm… I did it when I was a kid so it isn’t that difficult. I drilled a couple of holes in the end, popped in some 3.5mm jack sockets and then soldered them on to the piezo pickups. (I also had a couple of sockets floating around inside – I think I ran out of the surface mounting jobbies.)

    “So the pads send out triggers and the Synsonic can be triggered by 808 / whatever trigs. I triggered mine from my 808 and Rogue and I played poly chords from my JX-3P sequencer by whacking the pads. Great fun! I’ll try to dig it out and put up a pic.”


    Apparently the connections to the piezos are bi-directional. I’d experiment with a resistor in series with each jack, say 1k-10k, just to be safe.

    I don’t have the patience to search the rest of that thread.

  • Sorry to keep changing things, but I can’t stop tinkering. Nearly all my previous mods have been revised and, I think, improved. Rather than take up space here with slightly changed schematics and verbose text, I made an Update page on my website.

    Here is a summary:

    Impact for the Snare and Tom-2 has been improved by replacing the switches in the earlier mods with pots and changing resistor and cap values. The Hi-Hat/Cymbal has a better Tone control. Slight changes to Tom-1 Sweep Depth now enable pitch sweep down — a quite unnatural sound — as well as up and none. On my page you will find schematics, more details and a few wiring examples.

    I’ve high-lighted a few more signals (mostly Ground and supply voltages,) on the Component Layout drawing. http://www.sdiy.org/richardc64/synsonic/comp030609.gif

    I’ve updated the large schematic
    http://www.sdiy.org/richardc64/synsonic/schema030709.gif , removing the caps that had no effect on the ticking sound after my drastic action many posts back of adding a 5 volt regulator. (And yeah, the ticking is still present and it’s really got me ticked off.)

    Sound samples:

    Varying Impact with minimum Decay,
    then the same with longer Decay and higher Tone. http://www.sdiy.org/richardc64/synsonic/snh_56.mp3

    Tom-1 Sweep
    High pitched with normal sweep, then gradually reducing, then reversing.
    The same, but starting at a lower pitch.

    Medium pitch and Decay and varying Impact.

    Varying bass-treble tone pot

  • Hi. Cheers to Richardc64 for all the in depth info. Very helpful! I added a highly liquid msa-t and it works great. Even managed to get 2 different velocities for the 4 sounds (different pitches for tom1) so all 8 of the triggers got used.

  • Hi Guys!
    Today I planned to start the modification of my synsonics. When I looked closely at the board this time, I discovered that my board is slightly different (or even a lot). Is there anyone that has the same board as me, or could someone point me out to the places that are marked as A B and C on the mods page. Any help will be hugely appreciated. below are the pics of both sides of my board.

  • Wow! That’s *really* different!

    The first thing I notice, after the different layout, is there’s no MM5837 noise generator. But there’s an additional 4558. That might be used to amplify a reverse-biased transistor (or zener diode) noise source. On the other hand, it may be that the noise is incorporated in a revised Drum Sound IC. (24 pins.) Can you read off the full numbers (and count the # of pins) on that IC and the uC, so we can possibly determine whether they’re same as used in the original? It looks like the Drum Sound IC has an XR marking. Mine doesn’t say that.

    Seeing as how info on the original Synsonic was so hard to come by, finding info on that revision will be a real challenge. Your only recourse may be to poke around blindly or trace out the circuit and compare to the original. Look for “landmarks,” such as which pins the piezo pads connect to, which pins communicate with the uC. If they’re the same as in the original, it’s likely those ICs are unchanged.

    It looks to me that the uninstalled components around the 2114LC RAM are for the battery-backed version, retaining stored patterns when the unit is turned off! Without a schematic with parts values, it’d be just about impossible to provide that feature.

  • Hi,
    regarding the different board I actually have one as well. It looks different at first glance, but I assume it is the same as I followed your instructions on modding it and it worked fine. The resistors and caps etc are labelled the same, have the same values but are just in different places.

    Anyway, on to my question. Whilst doing the said mods I somehow managed to stop the Synsonics “sequencer”? working as well as the LEDS. The drums trigger fine, but I cant use the roll, record functions Etc.
    Any idea what I should be looking for?

  • Sounds like the microcontroller has quit. If the Accent button still shortens the decay of the cymbal then the micro is still doing some of it’s functions. Perhaps there’s something wrong in the button/led matrix? A short somewhere, maybe.

    If even Accent doesn’t work, check that the MPU Reset pin 7 isn’t held at ground. Also check that the clock (Pins 1 and 42) is ok.

    Other than that, I have no ideas. Download the Service Manual and follow the steps in the troubleshooting flowchart. I didn’t see anything helpful there, but maybe I missed something.

    The circuit you have can’t be entirely the same as the original because, as I said, instead of an MM5837 noise generator there is an additional 4558 dual op amp. My mods have nothing to do with the micro’s operations, but that was on the OLD board.

  • Ok, cheers for the advice. Sorry misinformation!

  • ok….i got two synsonics on the way and was inquiring about the accesory pedals….could someone explain a lil on what i need to do to to make one. im kinda confused and was wondering if someone could explain….thnx!

  • Take a look at this comment.

    Basically, you just need to rig 2 momentary switches – One switch will connect to pin 1 and ground for bass drum, and the other will connect to pin 2 and ground for open/closed hi hat. Ground can be taken from pin 3. You can cut one end off of a midi cable and connect those wires to your switches.

  • wow a second look at what i ordered reveles that it is a slightly different version that has two speakers encased, thus makin it longer and a tape input? but i was wondering if you can do the mods for some dough?! i have not the time and dont trus myself enough, plus i have freggin potato fingers too. but yeah get back at me and let me know whats good..thnx for your time!

  • wow..thanks that worked. i had a few more questions
    okay, is it possible to add volume pots
    and also how are the diffrent triggers set up, can you make the bass drum trigger on 16ths like the others
    and finally can you sync up two synsonics?
    kool i would like to do this mods myself so once again, could you point me in the right direction….thnks again cosmo

  • Hello again… thanks for all the tips an such. Well I had some crazy ish happen to my synsonics pro… it was messing up, but in a good way. Ok, well I guess my batteries were low and when I turned it on it was making a
    continuous tone that was obviously coming from the pitch control of tom 1
    and I could control the tone of it with the pitch control, and it ws going
    good for quit a few minutes! crazy huh?! But I know its not permanent,
    but ohh how I wish I could make it permanent!

    I know you have probably moved on from the synsonics, but I jus cant
    put the thing down and to think it may be possible to have a bassline
    modification, I am stoked. Please tell me its possible. I am new to this
    sport but am learning quickly and doing my research. I appreciate all the

  • Ya, a “bassline mod” is totally possible!
    My bandmate Thom did the same thing with a similar drum toy. He found that those piezo drum pads send out little voltage spikes, which trigger the sound. If you replace that spike with a constant voltage, the drum tone stays on as long as the voltage is there! Find where the piezo pad connects to the board, and try experimenting with a low voltage, like one AA battery (1.5V). You might want to put a trimmer pot after the battery, to dial in on a good value. Also, RichardC64 has done some great mods, including decay controls:

    Oh, and as for your other questions:
    Volume pots can most likely be added to the output resistors shown in the second diagram at the top of the page. Try connecting them to ground thru 100k pots. (I’m sure RichardC64 will correct me on this if i’m wrong)

    Bass drum triggers- That might be possible, but i don’t know enough about the logic to figure it out at the moment. I would think you could tap into the triggers generated for the other drums… However, it is possible to trigger the bass drum externally see this comment.

    Syncing 2 synsonics- you’d think it would be possible, but i dont’ think anyone’s figured that out yet!

  • Well, there’s nothing to correct, really. But as Justin noted at the very beginning of this thread, the snare and toms are each made up of two sounds: tone + click for the toms, and noise + click for the snare. You’d need six separate pots for all those, plus 1 for the cymbal and another for bass, if you so choose. Or you could combine the two signals for each voice into 1 pot. OR you could have a pot that varies the balance between tone and click (or noise and click,) and follow that with another pot for the overall level. I have not tried any of this. I’m satisfied the levels as is, and am in fact trying to minimize the number of pots I’m adding.

    What do you mean by bass triggers? To trigger the Synsonic bass from an external source all you need is logic 0 at pin 4 of the accessory jack. If your triggers are positive, logic 1, you’d need to add a cmos inverter powered from +5V. Simpler than that would be to connect the collector of an npn transistor to pin 4. The transistor’s emitter connect to ground and positive pulses connect to a resistor — say 22k to 100k — to the transistor base.

    To get bass triggers from the Synsonic is a little trickier. Those exist as low-going pulses at pin 10 of the microcontoller. This would definitely need to be buffered and inverted before going to the “outside world” to avoid blowing up the micro.

  • btw, this thread was mentioned at Highly Liquid
    which leads to a vid at youtube

    btw #2. Yahoo will be shutting down Geocities later this year, so my links will go dead — unless Yahoo has the courtesy temporarily provide re-directs. I won’t hold my breath. Anything not hosted here at burnkit will vanish. I’ll update y’all when I get a new host.

    btw #3. I found a ridiculously simple fix to the limitation of the range of the pedal I use to open/close the hi-hat: Instead of +5V I connect the “bottom” of the pedal pot to +9V. I don’t expect many of you have done that particular mod.

    btw #4. Nice new look here.

  • OMG! I just noticed a MAJOR discrepancy! The illustration of the Accessory Jack shows the Bass and “Accent” triggers on pins 1 & 2, respectively. but the Synsonic schematic shows them on 4 & 3! The schematic numbers the pins in a different order.

    Which graphic is correct?

    Here’s a quick C&P schema of what I suggested for positive Bass triggers In and Out, above.

  • Richard- As far as i can tell- both the ACCessory jack diagram AND the schematics use non-standard pin numbering schemes. Added to the confusion- the schematic seems to be looking at the BACK of the jack, from the INSIDE of the synsonics, whereas the ACC jack diagram is looking at the FRONT of the jack, from the OUTSIDE.

    At least one person has made bass/accent pedals using the diagram- he mentions the pin numbering differences in his comment.

    I’ll try to clarify the diagram. What do you think, should i use the standard DIN numbering system, or the pinout from the schematics and say “view from OUTside?”

  • Justin said: At least one person has made bass/accent pedals using the diagram- he mentions the pin numbering differences in his comment.

    Oops. I missed that, no doubt because I don’t plan to use that jack in any manner.

    I think the simplest thing to do would be to leave that graphic as-is, and expand the Note under it to stress that the pin numbering shown is non-standard; not DIN or MIDI.

    I’ll change the numbering on my enlarged & enhanced schematic to reflect whatever you decide to do about the numbering. Additionally, I can edit the original schematic, insert that into the Manual zip file, and make that available to replace what’s in the manual library. How’s that sound?

  • I haven’t lurked on this site in a couple of years. I just read through the posts (nice stuff all) and wanted to make a comment about the 12 pulse vs. 16 pulse difference between the Synsonics and Midi (if I’m covering old ground, many apologies). The Synsonics predates midi by a few years, hence the non-compliance. I believe, had midi been in place when the Synsonics was developed, it would have used the standard. This also explains why the Synsonics has a non-midi DIN connection.

  • P.S. This doesn’t have anything to do with circuit bending, but I did record a song that uses synsonics drums almost exclusively. Thought you might enjoy a spin of it:


  • Great stuff. been reading this and getting myself amped up to do an intense mod using some of the ideas presented by richard. I was thinking about cutting a few traces for snare and cymbal and inserting a bandpass filter. but really these mods are great. i love this unit. although the hissing is far too much for me to record with, i need to find if i can minimize it. also anyone notice that the cymbal sounds wonky when you turn the gain up? its got a bit of an oscillation in it making it sound like a fat mans fart.

    anyways, cheers.

  • Good luck with the bandpass idea. I didn’t have any success with that, but maybe I chose the wrong filters to experiment with, or maybe I was just having a run of bad luck. There are numerous Wah and other effects that might be suitable here:

    As for the hiss, I suspected the LM386s. It turned out I was right, but for the wrong reasons.

    I desoldered U5 and U6, installed sockets and plugged in new 386s. This had no affect at all on the hiss. Pondering the situation, I came to the following reasoning and conclusion: While not exactly high quality amplifers, the LM386s are not especially noisy devices, but because the Synsonic’s design used these Power Amplifiers as both headphone drivers and line-level drivers, the signal into them had to be kept to a low level. This was accomplished by making U4′s op amps attenuate, not amplify, the signals from Drum Generator U3. That, I believe, worsened the signal-to-noise ratio of U4, causing the excessive background hiss, which was inadequately dealt with by low-pass filtering capacitors in the signal path. (C24, C16, C26, C18.)

    With no LM386s in the sockets, I took the signals from the wipers of the LEVEL pots, then increased the gain of the op amps so they would amplify, instead of attenuate, by increasing the feed-back resistors R47 and R53. The result was greatly reduced hiss, but because R47 and R53 had been increased, C16 and C24 had to be decreased so that there would not be too much loss of high frequencies.

    I used “barrel” RCA jacks for the new outputs, but to retain the original Line Out jacks and, more importantly, NOT desolder the LM386s, which is a risky operation, follow these steps:
    Find the trace connecting the ’386(s) pin 3 to two capacitors and cut it. If the 386(s) are not removed, they MUST be disabled in this way, otherwise they will be overdriven by the new, larger input signal and draw too much current and possibly burn out and cause who-knows-what damage. Cut resistors R57 and R61 and solder a 2.2uFcapacitor from each Line Out jack (J2, J4,) center to the appropriate wiper of the Level Pot(s).

    The LM386s can be retained as Headphone drivers if the increased signal into them is reduced. Since inside the IC pin 3 has a 50k resistor to ground, all it would take would be to solder a resistor of 100k or more across the cut that was made in the trace to pin 3. Here’s a schematic.

  • I just opened my synsonics and was disappointed to find I had the different version as well. After poking around for an hour or to I came to almost no conclusions. Just curious to see if anyone has made progress on these versions? I would love to have my 606 clock this thing!

  • It’s been a while since i’ve studied the schematics, but i remember thinking that external sync would be tricky. I don’t think i saw a place where the tempo clock line was isolated, but i could be wrong about that.

    However, it shouldn’t be too hard to have the 606 accent outputs trigger the synsonics drums.

  • I just opened my synsonics and was disappointed to find I had the different version as well. After poking around for an hour or to I came to almost no conclusions. Just curious to see if anyone has made progress on these versions? I would love to have my 606 clock this thing!

    Locate the connector for the drumpads. If it’s like the older model, four of those pins will be ground, the other four will be the \hot\ of each pad. You can patch external pulses to those pins through capacitors. Try .01 to .1uF to start.

    In the older model, looking at the component side of the board with the power jack on the right, the sequence of pins is:
    Tom2, Gnd, Snare, Gnd, Tom1, Gnd, Cymbal, Gnd.

  • Follow up: A friend has told me that to interface 1mS 5V triggers to his Synsonic \…I ended up just using a diode with the anode attached to input and cathode to the pcb trigger point (pins 9, 10, 13, 16 on U3 I believe were the numbers) and it works like a champ. Not the ideal protection scheme, but it works for my application.\

  • Hi everyone.

    I just picked up a Synsonics kit last weekend for a buck! It works fine, but I was wondering if I could install 1/4\ female jacks to each of the piezo’s in order to use the pads to trigger the sounds from my Roland TD-3 brain. I am asuming the Synsonics’ pads will work like any of the Roland external pads. Lastly, would I need to power up the Synsonics pad in order for them to work?

    In Richardc64′s Mar 11, 2009 post, it would appear possible:

    \Hi. I stumbled upon another way to modify the Synsonic:

    Jyoti at moogmusic.com forum

    “Ummm… I did it when I was a kid so it isn’t that difficult. I drilled a couple of holes in the end, popped in some 3.5mm jack sockets and then soldered them on to the piezo pickups. (I also had a couple of sockets floating around inside – I think I ran out of the surface mounting jobbies.)

    “So the pads send out triggers and the Synsonic can be triggered by 808 / whatever trigs. I triggered mine from my 808 and Rogue and I played poly chords from my JX-3P sequencer by whacking the pads. Great fun! I’ll try to dig it out and put up a pic.”


    Apparently the connections to the piezos are bi-directional. I’d experiment with a resistor in series with each jack, say 1k-10k, just to be safe.\

    Thanks in advance for your help.

  • BB-3D wrote:
    ‘… I was wondering if I could install 1/4\ female jacks to each of the piezo’s in order to use the pads to trigger the sounds from my Roland TD-3 brain’

    The post at moogmusic.com forum seems to be saying that that is possible. I don’t think the Synsonic needs to be powered.

  • Thanks Richard.

    It seems like I did read that correctly.

  • @ruin

    I had that problem also when I used a (mono) guitar cable to plug my synsonics headphone jack into a channel of my interface, I found though, that if I used a 1/4″ stereo to two 1/4″ adapter to go from the headphone out into two channels (in stereo) it sounded just fine. Hope that’s helpful.

  • @ryan mcryhew

    I also have an alternate board layout, it’s a similar layout to the pics posted by Ronnie

    The area labelled A in the diagram at the top of the page is in a similar spot on my board. slightly more to the left ( when looking at the bottom of the board; look for the parallel rows of 12 pins). I just finished adding vol and decay controls for the snare and hihat, a decay mod for the tom that you cant tune, a sweep length mod for the tom you can tune, a touch contact point that seems to make the snare turn into a weird gritty crash for a second until it dies to nothing (returning to normal after you take your finger off) and a control for the global noise/impact ratio. All of my mods except the touch point of death and noise/impact control were done by putting 100k 50k or 1m pots between points in the “A” area with one point I found toward the right side of the board

    to find the mystery point: when looking at the bottom, trace a line with your finger from the lower RCA output across the board to your left. About an inch or so in, below your finger, you’ll see a group of 8 contacts arranged horizontally an two parallel rows of 4, if I remember correctly, the contact you want is the second from the left in the bottom row. If that doesn’t work, poke around, it’s in that area). not sure what that point is but I think its off of one of the ICs mounted there, I suspect it’s just bleeding control voltages off to ground, but I’m not sure, I just stumbled upon it with alligator clips. Anyway, play around with pot resistances.

    One unique thing about my board is that it had a built in mini pot on top of the board (unnaccessable from outside though) which controlled the noise level. I don’t see it on ronnie’s board, though the res of the circuit looks the same. I just bridged the contacts with another pot which is mounted where I can get to it after the unit is closed. The touch point of death can easily be found by just poking around with your fingers.

    my next endeavor will be adding midi, right now I’m still trying to figure out how to get full velocity sensitivity from the midi>volt pulse conversion. The Highlyliquid MSA solution is nice, but I think it’s be so cool to have more than just 2 velocity levels. Any new Ideas on this front?

  • Just realized I may be able to use the Silent Way Trigger plugin to send trigger signals to the inputs I added to my Synsonics drums. Sounds plausible, I’ll post results when I get a chance

  • hey burnkit gang ! love the site , totally radical info!!
    anyways got myself a synsonic today at work , i work at a rubbish tip , its amazing the stuff ive scored from there , analog delays, reel to reels , pretty much every switch/wires /etc etc everything i ever need ..
    k well turned the synsonics on all works fine except for an overzealous hum sound that seems to be relaTed to the tom2 .. as when i use the accent buttons on tom2 i can hera the click slightly pulsing the hum/tone.. all other sounds & controls are fine …. this seems to be a common problem for this budget box ?? totally cool little machine it would be great if i can fix it , has anyone found a fix for this ?? otherwise can i just eliminate this ? im assuming its a prob with the tom2 so can i just remove a part of the circuit ??
    thumbs up burnkit … just about finished my hr16 with thanks for alot of info iv got off this site … i have a patchbay and a totally nuts old school joystick controlling my bends on the hr .. Rock on
    much love from sydney australia !!

  • Yes, the hum is a common problem, but there is a fix listed in the service manual. Read mosquito’s and Richard64s comments above. Cool, m8, would love to see pics of your hr-16 when it’s done!

  • Hello Justin

    Great site. Although most of what you’re talking about goes way over my head! I’m no circuit bender and an entry level solderer but I have a synsonics mod question for you.

    A band I work for uses a synsonics live in the following way: the drummer tapes down the tom 2 button so that it plays a 4/4 beat and adds additional snares and occasional live drums over the top. To stop it he lifts the tape. My question is… is there a way to swap the bass drum for the tom 2 so that when the Bass On/Off button is pressed the tom2 sound plays instead of the bass drum?

    Alternatively do you have any suggestions for a different button that would hold the tom2 on without tape?

    Hope you don’t mind me posting such a boring question.



  • Stu- the easiest way to do what you want is to mount a new toggle switch that connects to the tom button. Open it up and find the connections that go to the button. You may have to follow them a bit to find a good place to solder to.

    But you know- the synsonics DOES have a RECORD mode. Is the drummer too lazy to program a 4/4 beat on the synsonics and then play it back? :p

  • Thanks for such a quick reply Justin

    I have suggested the record option but they haven’t gone for it. I’m going to suggest a spring clamp for the next gig and then try the toggle switch. Better start learning some basic electronics!


  • Anybody be able to give me a tip as to what amperage or ma to get wall wart? I see 9v and a phono1/8″ jack, i can see the traces inside that suggest +tip…
    Thank you for holdin this site up!
    I’m always lookin for more Burnkit2600 music videos btw. All genius! imo.

  • bah I found it in the service manual 200 ma minimum.

  • Glad we could be of service! ;)

  • I have two on bench right now. got the triggers workin (Thanks to tips found on this page! )1/8″ jacks triggerin from tr505.
    messin with separate outs and separate volume pots tonight.(any tips would be appreciated) I would like to do both. Plannin on mountin each one on a 1/4″ piece of plywood with metal faceplate for the new components.
    Thanks again !

  • btw i triggered the kick drum and cymbal accent by wiring a jack to the corresponding ping under the din jack. hope it dont fry!

  • Awesome! For individual outs I would use switching jacks, wired so they take that drum out of the main mix when you insert a jack. And if you’re going to do volumes, you could also do pan pots. Also do the noise reduction cap replacement mentioned in the service manual.

  • did anybody get pitch on tom2 to work ?
    i was messsin with a pot on c5 and ground but couldn’t get any change.

  • Does anyone know how to trigger the Synsonics bass drum with the TR-505? I don’t know where the trigger input for the synsonics is to enable it to be triggered by my 505.

    Any help on this would be greatly appreciated!

  • I haven’t tried myself yet, but i think people have been tapping into the piezo triggers on the synsonics. The piezos output a small voltage spike when hit, so a similar trigger spike from something external should work, too.

  • Thanks Justin for the reply. Do you know where the bass drum trigger is on the synsonics?

  • Oh, I was thinking about the toms, not the bass drum. The bass drum can be triggered thru the accessory jack. Read the section about that- Shorting the bass drum pin to ground acts as a trigger. I think people have used vactrols to trigger it with an external pulse, check the comments above…

  • I’m interested in substituting the synsonic’s internal clock with an external source. has anyone done this? any tips? I have successfully substituted the 505′s clock with the synsonic’s clock (which is 16 ppqn so the 505 has to be running in triplet scale to sync up)

  • I remember looking at the service manual and thinking it wouldn’t be easy. There is a system clock, but it’s in the MHz range, not the ppqn range.

  • Hi list,
    I’ve been reading the synsonics blog here.
    I’m quite impressed with the number of very technical and useful posts.
    I had a synsonics back when they first came out and I tried to do some
    mods to it and broke it and threw it away, and forgot about it.

    Recently, a client brought one in and I fell in love with it all over again.
    I found one on Craigslist for $75.00 in PERFECT condition.

    I’ve read about the microprocessor being VERY touchy.
    And I’ve even sent out some inquiries about doing mods for a synsoncis.
    They have all come back with “It’s too touch to work on.”

    I did study electronics in High School and could probably do the mods myself
    using the schematics that members have provided, but with that touchy
    CPU, it just seem to risky.

    One thing that no one on the list seems to have talked about is
    relocating the motherboard to a rack.
    This is in fact what I’d like to do.

    What I’m thinking about doing is buying a second unit and keeping the one
    I just purchased “Stock.”
    This second unit I would like to do all of the mods for pitch and decay for each drum. Also trigger inputs and separate outputs.
    I’ve also read about upgrading the output vca to get rid of that awful hiss.
    I’m not sure if that would apply to a separate output mod?

    So the idea is to get a single space rack box and put all of the knobs on the front,
    and all of the jacks on the rear. The buttons and pads would not be needed and
    could stay with the unused case. The main volume and tom 1 pitch knob would relocate
    to the front of the rack. The entire unit would in effect become a module.
    And then I would think of installing a midi to trigger board as well as the
    trigger jacks that could work in parallel.

    What do all of you think of this idea?
    Does anyone feel up to doing some of the mods for me?
    I can build the case and install the jacks and knobs,
    but I’m not sure about installing all of these components on this
    very sensitive circuit board.

    Please reply to the list or through my website.

    Bill Williams

  • Hey Bill,
    It sounds like you’ve got some lofty goals.
    Personally, I’d keep it in original case as its design and hands on playability are more then half its charm.
    That said, its still quite doable though, but with a lot of work. I’d be up for giving you a hand if you’re serious.

  • Bill,

    For all that trouble I think you might be happier just getting something from the Tama TechStar line, or one of the lesser expensive Simmons SDS models. Those have trimpots for EVERYTHING, individual outputs, trigger in’s (MIDI retrofit is easy) and they sound GOOD with no hiss. Here’s my SDS800 for example:


    The main difference between one of these and your proposal is that to get all those trimpots in, these units are not usually smaller than 2RU. I racked my SDS800 – which I believe is the knobbiest of the lot – and it takes up about 7RU.

    What is the replacement VCA for the Synsonics? That’s the one thing I hate about mine is the godawful hiss.

    all my best,
    - Scott

  • I modified one using Richard’s mods:


    The board in this one is a different revision, so the above output points don’t work the same. That whole section of the board is wired differently.

    There are some build pictures on my blog:


    Thanks for all the great contributions by everyone here, they are really helpful!

  • Hey everyone – great page!

    Does anyone know what transformer is in this? I just bought one of these but it appears that T1 is dead. Hope fully this part is still available. Thanks!

  • have you looked in the service manual?

  • Hey Justin! I have actually. TY77?
    I haven’t found info on this thing anywhere.

  • Hmm… yeah, that’s a weird one. 10 pins, round. Mine says it’s made by TDK., but I’m not finding anything online… I wish I knew more about transformers, sorry!

  • Interesting. Mine doesn’t say that. Even that’s helpful. I’ll look around and report back if I find anything. Thanks!

  • This thread is awesome! I just currently got into modding the synsonics. I am going to be using a +5v trigger system in order to trigger-in the individual sounds. Adding a switch on the hi-hat for open/close contacts from the din. All sounds will have 1/4″ mono individual outputs. I will also add 10k linear pots for the incomming 0-5v cv pulses to control the sensitivity or loudness of each hit (haven’t tested that one yet but think it will work). As far as triggering the bass drum with this system, all I can come up with is adding a 5v electronic relay that will connect the din bass jack to ground whenever it receives the cv pulse. I am also going to try and put a pot between the bass din and ground to see if this does anything. Thinking about it I will try this with a pot between the hi-hat close pin and ground as well. If anyone has ever tried these or has any suggestions please feel free to let me know.

  • Those all sound like good ideas! Instead of a relay for the BD trigger, maybe a vactrol will work? Not sure what a pot will do inline with the BD trigger, try with a very small value pot – you may be able to get random stuttering or something weird.

  • I looked at the schematic and found that I do not need a relay for what I want to do. I am going to cut the resistor R17 to break the +5v trace that goes to the bass drum line accesory jack and wire in a 1/4″ mono (tip to H2 bass drum line and sleeve to the footswitch ground) and feed my +5v triggers through there, I hope it works. When I get to assembly and testing I’ll let you know how it works out for wiring in the pots for the individual cv trigger control 0-5V, i’m hoping it will control how hard and how soft the audio for the sound hits like a sensitivity knob (instead of individual volume control).

  • Guys, this site is awesome. Thanks for all the info (including the comments)!

    I’ve had a Synsonics drum machine sitting on a shelf for years just waiting for info like this! I tried the footswitch stuff last night with some gator clips and it’s going to be perfect to open this guy up a bit more. Thanks again!

  • People is it normal that it is very noisy without anything being played? I have a stereo pro model, the one with speakers.

    Is there any trick to removing the noise?

    Thanks for your reply!

  • It is noisy normally. I think there is a capacitor that can be replaced.

  • Hi guys,

    I’ve had the Mattel for some time, and played around with when i was a lot younger. I recently revisited it to use it as part of a live setup, to increase the inexactness and dynamic, etc., of live electronic music. It was unfortunately unresponsive, but upon probing around with a voltmeter, I concluded that the noise generator chip was fried. (I then remembered also frying it with 220V accidentally while traveling). I found the chip online (from a pin ball machine restoration forum !) and swapped it in and everything is working just fine !

    Now I am interested in integrating midi control. I would like to have both accessibility to controlling the unit via midi, and preserving the pads and keypad functionality.

    From the limited research I have done, the Highly Liquid MSA-P (http://highlyliquid.com/support/docs/pdf/MSA-P-Hardware-Rev-K.pdf) would serve well to trigger the drums. My question(s) regard this triggering.

    1) Would the SPST type switch output of the MSA-P be able to trigger the Mattel drum sounds? If so, could you point me towards info regarding where exactly to solder these MSA-P output connections? (I’ve downloaded and inspected the service manual)

    2) Is there any information available pertaining to the voltage/amperage requirements/limits of these connections? The outputs of the MSA-P have variable voltage.

    (I read somewhere in the above that you were interested in investigating controlling the clock in the Mattel with midi? Have you made any progress in that goal? I think it would be a great way for me to eliminate my desire to control the Mattel with a computer (seems a bit sacrilegious…).
    My goal is to have the note devisions of the keypad sync with the tempo of a live set (because playing with the keypad is primo!). Currently, I am unable to do so, and simply use the pads. I loop them via ableton live (clocked) to ensure there is no drifting, but I am missing out on 7/8′s of the fun of using the unit :( … and I would still be even if I were to midi control it with my computer.)


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