Circuit Bending and Modifying the Alesis HR-16
- Sample and OS ROM upgrades
- Custom Sound Chips
- Adjustable Pitch Modification
- Circuit Bending the sound ROMs
- HR-16 Service Manual
- HR-16 Owner’s Manual
- SR-16 Owner’s Manual
UPDATE 2013 Sept
Added pitch mod info, bunch of new photos, etc.
UPDATE 2010 Nov. 26
- Upgrade your HR-16: sample and OS chips are for sale.
- HR-16 custom sample ROM software is available for free (non-commercial) download!
CEG v 1.4.2 (windows) Setup_CEG_V1.4.2.zip
Like most digital drum machines from the 90s, the HR-16 is great for circuit bending. However, it can be a bit unstable, even when unbent. Take a look at the service manual- it is a long list of repairs and upgrades. I wouldn’t recommend it as a first bending project. If you get into bending HR-16s, you will most likely end up having 3 or 4 HR-16s in various stages of disrepair, scavenged for parts for your one working HR-16.
Common repairs are: replacing the internal battery, SRAM chip, volume and data faders, LCD screen, and repairing the button conductivity. Eventually, I’ll post more detailed info about these repairs…
Sample and OS ROM Upgrades
The original grey HR-16 came with acoustic drum samples. Alesis later released the black HR-16:B which featured more “modern” electronic samples. The HR-16:B also came with an upgraded operating system, 2.0, that was more stable and had new features like SYSEX MIDI dump. Some musicians still preferred the original acoustic samples, so Alesis released a version of the 2.0 operating system for the original HR-16. The label confusingly reads: “Alesis HR-16:B & HR-16.” The startup screen does not display an OS version number, but as far as I can tell, it is more or less identical to the HR-16:B OS 2.0, except it is compatible with the original acoustic HR-16 sample ROMs.
An HR-16 or HR-16:B can be upgraded or “downgraded” by replacing the OS and sample ROMs. Alesis was kind enough to put the OS and sample chips in sockets for easy removal. If you have an EPROM burner, you can burn the rom files below onto EPROMS to upgrade or downgrade your HR. For OS chips, use a 27C256 EPROM. For sound chips, use two 27C040 EPROMs.
The SR-16 is based on the HR-16. You can almost think of it as HR-16 v3.00, but it is not compatible with the HR line at all. I’m including the SR-16 ROMs here in case anyone wants to compare them with the HR-16. Since both the SR and HRs use the same size sample EPROMs, you can try swapping chips between machines to get some weird sounds, if that’s your kinda thing. ;]
HR-16, HR-16:B, SR-16 OS and sound ROMs:
HR16_V2_0.BIN : HR-16 OS V2.00 “HR16:B & HR-16″ (most current)
HR16_V1_09.BIN : HR-16 OS V1.09 (outdated)
HR16_V1_07.BIN : HR-16 OS V1.07 (outdated)
HR16_U15.BIN : HR-16 sample ROM: IC U15
HR16_U16.BIN : HR-16 sample ROM: IC U16
Custom sound chips:
I was able to reverse-engineer the sample data, and I burned new sound chips with custom samples!
They are available for sale here:
HR-16 Custom Sample ROMs
And I’ve posted detailed DIY instructions here:
HR-16 DIY Sound ROM Tutorial
Adjustable Pitch Mod
It is possible to add global pitch control to the HR-16 by installing a high-speed clock circuit. One common circuit uses an LTC1799. They are sometimes available at circuitbenders.co.uk and at getlofi.com. Below is a photo of the basic circuit you need to build- you have to add a limiting resistor and a capacitor, as well as wires to connect to power, control potentiometer and clock output.
You may think that you need to replace the crystal, X1, as with other pitch modifications, but that will adjust the clock speed for the whole machine, including tempo. A better method is to replace the clock signal that controls how fast the samples are read from the EPROMs. That signal can be found going into pin 37 of the ASIC chip, as seen in the photo below, courtesy of Squidfanny. You will need to cut the trace that goes to this pin and solder a new wire that will send our new clock signal to pin 37. You can choose to ignore the original clock and replace it with your adjustable clock, or if you want to be able to snap back to the stock pitch you can use a switch to toggle between the new signal and the original signal from the cut trace.
You may prefer to solder all your wires to the bottom of the board, as seen below. On the left, you can see the connections to the address and data lines of the sample chips for circuit bends, which are explained later… Towards the bottom, you can see a wire connecting directly to ASIC pin 37, and another going to the cut trace that originally connected to ASIC pin 37. Towards the right are two wires for power to the LTC1799. One connects to the ground found near the sample ROMs, the positive wire connects to the 5V regulator. The small orange wire was there originally, probably from when the machine was serviced last.
Circuit Bending the sound ROMs
UPDATE: Stay away from the “PCM54HP” chip! A couple people have said they did damage to their HR-16 when trying to circuit bend that chip. Gordonjcp says: “The PCM54HP is the DAC that turns all those numbers into sounds. It may well have fairly high voltages on it – not dangerous to you but well above the 5V that the logic chips expect!”
The HR-16 and HR-16B are great drum machines on their own, but there are tons of wonderful PCM-scrambling bends hiding inside. The sound ROMs are the two 32-pin chips. They are read-only versions of the 27C040 4-meg EPROM:
Connecting different combinations of pins on the sample ROMs yields flanges, distortions, gating, ring mods, etc. Some pins even output synth-like tones when you connect them to an audio amplifier. You’ll want to stick with only the address, output and GND pins. Avoid the VPP, VCC, /CE, and /OE pins.
The hard part is coming up with an interface that lets you use the bends effectively. This HR-16:B was a commisioned piece i did for Sam Spiegel (N.A.S.A., etc). He wanted something crazy that utilized as many combinations of bends as possible. I used 4 pairs of 6-position rotary switches.
Each pair is wired together, for a total of 6X6=36 bends per pair.
Each pair can be turned on or off with the 4 toggle switches. It starts to look like some WWII-era German Enigma machine when you calculate the total possible configurations this thing can be in. According to my math, the total possible configurations is 1.78 MILLION! The LEDs indicate what bends are active, and plus they just look rad.
There are countless options for interfaces! I’ve re-wired old TV remotes and video game joysticks so that each button, including up, down, left and right will turn on a different bend. The joystick is connected to the HR-16 via an RCA patch bay. I like this method also, because you can “play” the bends, instead of just putting the HR-16 into different modes.