Hack! Common Synthesizer and Drum Machine Modifications

Not every used synthesizer or drum machine you buy will be in the ideal condition. Some will have road wear or other cosmetic dings, while others could be in need of internal repair. However, some may be in perfect working order—only a different working order than the original manufacturer intended. We’re talking about after-market modifications: these changes can range from small hacks to fairly complex changes to the actual circuit boards.

In this story, we’ll introduce some of the more common mods for synths and drum machines that you may encounter while shopping. If you already own the instrument, you may want to consider installing these mods yourself or paying a professional to do it.

A Brief History of Instrument Modifications

Musicians and engineers have been modding electronic instruments almost from the very beginning. The Minimoog, Moog’s revolutionary 1971 instrument, may have been the blueprint for non-modular synthesizers at the time, but that doesn’t mean it was perfect: common mods included working in a ribbon controller, oscillator sync, pulse width modulation and CV/gate as well as, later, MIDI. When MIDI was standardized in 1983, many older synths were popped open to add DIN sockets (and still are).

On the drum machine side, new ROM sounds were slotted into digital units—Oberheim even released its own Prommer to make this easier. In more recent decades, circuit bending—or making changes to PCBs to affect functionality and sound—has become something of a cottage industry, with adventurous engineers and hobbyists creating bizarre new creations from old digital tech.

Tubbutec Mods

Tubbutec's Juno-66 Mod

Tubbutec is a German outfit offering aftermarket mods for classic synthesizers. Their most famous is the ModyPoly, a mod for the Korg Mono/Poly, Polysix and Poly-61synthesizers. Consisting of a new voice assigner chip plus cables and DIN sockets, it adds a number of useful functions to these Korg classics: these include new play modes with two-voice, three-voice, polychord and extended unison, sample and hold and triangle waves for the LFO, an arpeggiator/sequencer called Powerarp, as well as MIDI in and out. They also offer mods for the Roland SH-101, the Juno-6 as well as the 60, plus one on the way called Organ Donor—a universal MIDI interface for electronic organs, string machines and polysynths.

KiwiTechnics Mods

KiwiTechnic's Kiwi-106

Another well-known company is KiwiTechnics. Based out of New Zealand, they’ve been at it for a few decades now and offer a number of new boards for classic synths ranging from the Roland Juno-106 and JX-3P to the Korg Polysix and Oberheim Matrix-1000. Their PCBs offer a ton of new functionality that varies between instruments, but they also focus on modernization through bringing specs up to date. For example, the latest is a new mod to the JX-3P called Kiwi-3P Matrix: it ups patch storage to a whopping 1024 tones, introduces pulse width and three LFOs, plus a chord mode, arpeggiator and an improved sequencer. KiwiTechnics mods are often badged with Kiwi stickers on the instruments that make them easy to identify.

GliGli Sequential Circuits Prophet-600 Firmware

Prophet-600 with GliGli Firmware

Dave Smith’s Prophet-600—the first commercially available synthesizer with MIDI—was a good synth to begin with, but engineer GliGli made it even better with their firmware update. The update, which uses a Teensy++ PCB to replace the original (and slow) Zilog Z80 CPU chip, adds increased resolution for sound parameters, faster envelopes, a new LFO function generator, vibrato, unison detune, mix overdrive, an improved tuning procedure, and full control of parameters via MIDI. Unfortunately, the company manufacturing the Teensy++boards has discontinued them, so it’s tough to install the new mod, but existing ones are still out there and they’re highly desirable. There are even third-party panel overlays available to display the added GliGli functionality.

Vecoven Roland JX-10 Firmware

Roland Super JX-10

Roland’s Super JX-10 is a beautiful-sounding instrument with terrible MIDI implementation, so it was inevitable that someone would make an upgrade for it: engineer Vecoven has been releasing JX-10 improvements for almost 10 years now. The flash module plugs into the assign eprom without the need of soldering and adds new firmware, 32 banks of memory, and firmware updates through MIDI. He also offers a PWM kit as well as JX-8P upgrades.

Analogue Renaissance Roland Juno-106 Chips

Analogue Renaissance's Roland Juno-106 Chip

While Roland's Juno-106 is a bona fide classic polysynth, it's also something of a money pit. With voice wave generator and filter/VCA chips that are guaranteed to fail due to corrosion from melting resin, buying one means that you’ll have to do something about these eventually. You can either have them refurbished or pick up a set of clone chips from Analogue Renaissance, a Belgian instrument company that also happens to make replacement chips for the Juno-106. They claim that they sound exactly the same as the original hardware and online reviews seem to corroborate this. If you’re buying a 106, make sure that the chips have been addressed in some way, or factor the cost of the upgrade into your budget.

Real World Interfaces Devil Fish Roland TB-303 Mod

Real World Interfaces Devil Fish TB-303

Robin Whittle started modding instruments in the late 1980s, putting solder to PCB on Roland TR-808, Yamaha DX-7s and, most famously, Roland TB-303s. His TB-303 mods—dubbed the Devil Fish—are the stuff of legend, with Richie Hawtin aka Plastikman famously using one. Robin is still at it, having done more than 300 in his lifetime, and has continued to refine the mods over time. Added functionality includes MIDI, extra memory, overdrive, filter tracking, filter FM, and more. Devil Fish-modded 303s are very expensive but can really change the sound of the instrument. Robin also does devil Fish mods of 303 clones like the Cyclone Analogic TT-303 Bass Bot as well as drum machines like the Roland TR-606, Roland TR-808, and TR-909.

Korg Poly-800 Moog Slayer Filter Mod

A Korg Poly-800 with a Moog Slayer Filter Mod

Korg’s Korg Poly-800 was the first polyphonic synth to break the $1000 price range upon its release in 1983—this made it popular but as time went on, it became even more popular to hate on it. A new generation of musicians now embrace its unique chip and distinctly ‘80s sound, but for a long time users insisted that the only way it sounded good was with the Moog Slayer filter mod installed. This added knobs for filter cutoff and resonance to the front panel, liberating users from the incremental buttons that stepped through filter adjustments. With this mod installed, the filter can really scream—as in "destroy your speakers and ears" scream—so be careful when using it. Other mods you may see include the FM800, which adds frequency modulation to the filter, a switch to toggle between 12dB and 24dB modes (the original filter is confined to 24dB), and external audio inputs.

USB Floppy Drive Emulator

Gotek USB Floppy Drive Emulator

One issue common with older gear is that technology becomes obsolete or breaks down. Floppy drives were very common as a storage medium on samplers and workstations in the late ‘80s and through the ‘90s, but these days you end up with double the trouble when you consider the belt drives that often stretch out and fail. One way around this is to replace the drive on your gear with a modern USB floppy drive emulator, fabricated to be the same size as the original but instead of taking discs they have a slot for a USB memory stick. This increases the amount of memory you can store by orders of magnitude. While some might enjoy the meditative aspects of using slow-moving floppies, no one will argue that USB drives aren’t a hell of a lot more convenient.

Drum Machine Mods

Circuitbenders Roland TR-707 Mod

There are a number of mods for drum machines that add functionality or change the internal sounds. Korg’s Volca Beats is a fun and cheap drum machine, but a lot of people don’t like the snare sound. A common hack involves adding a capacitor to the snare circuit on the PCB for a higher pitch and more snap. Other modifications include MIDI out and individual outs. Roland’s TR-707 drum machine is a classic digital drum machine that’s popular with circuit benders. DAC distortion, pitch adjustment, and decay mods are all common. Roland’s TR-505 and TR-626 aren’t nearly as popular as their more famous older brothers, mostly because of the sounds. HKA Design developed ROM expansion boards for the machines, adding Oberheim DMX, LinnDrum, and other sample sets to make them more appealing. Another old digital drum machine with new sounds is Korg’s DDD-1. Korgdddmods has created PCB Expansion cards for them, as well as a number of ROMs with sounds from the TR-808, TR-909, Simmons SDS V, and others.