Hardware Hacking - Circuit Bending - Firmware Mods

[ Roland MV-8800 ] [ Yamaha RX-5 ] [ Alesis HR-16 ] [ Other stuff ]

Roland MV-8800:

The MV 8000 and 8800 series groovebox/production studios are amazing pieces of hardware. They pack a ton of DAW functionality into a pretty integrated hardware box. I love mine but there were small things I wanted to change or add so I took on the (way more challenging than I expected) project of modifying the firmware. At this point I am able to make changes to the 8800's main firmware and have made a few improvements/tweaks so far, including:

  • Project loading/saving for projects incorporates how many songs are in the project, so loading and saving times are much faster.
  • Some annoying popups are now gone
  • Small tweaks to wording, etc

I have much more planned too! There was lot going on to get to the point of being able to make changes and most of it is documented here at the mv-nation forums.

What I enjoy most about this project is it involves reversing both the hardware at a very low level (things like chip selects, registers, etc) and the software with many challenges along the way. I also learned a new processor instruction set and architecture (SuperH, thanks to Ghidra and a ton of autoit) and many other things as a result of all the work. Very rewarding, plus my old sampler is getting updated!

Roland MV-8800 Production Studio

tsop flash reader/writer pcb wiring homemade debugging cable

ghidra annotated disassembly

Yamaha RX-5:



Alesis HR-16:

Picked this up as "non-working" on eBay for $25. It had some issues which were easily fixed (screen was busted, battery dead). Did most of the recommended updates in the service manual, new screen, retrobrited the buttons and circuit bent it including a few types of bends I haven't seen on other builds.

The OS and both EPROMs are now external to the unit and can be swapped out for changing from the stock sounds.

The circuit bends on my unit are the standard ROM/RAM patch points of which I used tiny patch headers rather than banana or 3.5mm jacks. Any of these can be routed to momentary or toggle switches in addition to be being controlled via the 4 3.5mm inputs. These 4 inputs connect to a 4066 switch chip. When the chip gets a 5v signal, it "shorts" the 2 patched inputs, so you can externally control bends with something like an Ardunio, Teensy, or the gate/trigger output of modular synths. I had planned on wiring up all of the 16 pads to be triggered externally as well but the trigger pads at best can be triggered around 25Hz, notes can be triggered MUCH faster via MIDI.

I also did the standard LTC1799 pitch control, but with a few small twists. First a 3 way toggle to go through all the different ranges of the LTC circuit, and in addition to the pot controls, I made a vactrol out of a white LED and photo resistor and this allows me to connect up CV from my modular system to control pitch.

Other Stuff: