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Fixing a 30-year-old Roland synthesizer bug
- digitailor 4y agoThis is cool, so TL;DR: The 3rd gen run of a Roland early digital synth product had an unresolved timing issue causing pitch playback problems. Recently, investigation revealed they hadn’t accounted for an Intel MCU part sub. The spec indicated the sub part was running too fast. They downclocked it via crystal swap which destroyed the unit’s MIDI timing. So they located the control ROM instructions to modify to fix the resulting MIDI sync issue and burned a new one: 0x1A8D: 1D5Fh -> 1388h 0x215C: 17h -> 0Fh 0x216D: 1D5Fh -> 1388h That’s it. Surgical. I spent some time inside an early Roland sampler of this era during the pandemic. It’s really well engineered stuff that sounds great.
- Gordonjcp 4y agoI guess it makes sense that it would be a common divider ratio (5000) but $1388 leapt out at me from disassembling the Ensoniq Mirage firmware.
- deleted 4y ago[deleted]
- keepquestioning 4y agoThis reminds me of the binary patching done in The Martian film.
- tomcam 4y agoAh, relief. Big Roland fan but don’t have this particular piece of gear & had trouble following TFA
- montag 4y agoYes, I love that the entire fix is a 5 byte change.
- rob74 4y ago...plus the quartz crystal that you need to swap. And to get those 5 bytes into the ROM, you have to desolder that too unfortunately. But yeah, still cool.
- djmips 4y agoIt wasn't pitch playback problems it was vibrato rate.
- digitailor 4y agoI get what you mean, it was a temporal issue, but it’s a PCM synth. That’s sample playback, and vibrato in that context is a modulation of pitch of sample playback over time. It’s a pitch playback problem that was caused by too fast a clock causing too fast a pitch playback modulation. (The LFO being used to produce the vibrato effect being misclocked due to too-fast MCU, causing a pitch playback problem. The pitch playback modulation was at the wrong rate.)
- user5678 4y ago
- ajxs 4y agoAwesome work! I love the care and attention that people put into understanding these devices. I'm currently in the middle of a vintage synthesiser hacking project as well. Last year I made a fully annotated disassembly of the Yamaha DX7 firmware, and did some other technical analysis of the synth. Since then, I've been waiting for a chance to put this knowledge to good use. I found a DX9 on a local trading site, and I'm in the process of hacking its firmware to remove the 4-operator restriction that made it such an unpopular synth.
- tomcam 4y ago> Last year I made a fully annotated disassembly of the Yamaha DX7 firmware You beast!
- colejohnson66 4y agoFound it: https://github.com/ajxs/yamaha_dx7_rom_disassembly https://github.com/ajxs/yamaha_dx7_rom_disassembly It’s extremely documented. More than I was expecting.
- NexRebular 4y agoI wonder if DX100 firmware could be hacked like that as well, it being another of the 4-op beasts too
- ajxs 4y agoUnfortunately you can't add any more operators to the DX10, however you could probably add multitimbrality! Yamaha's YM2164 sound chip at the heart of the DX100 is pretty well understood, and very similar to the later YM2414 used in the multitimbral TX81Z.
- pinewurst 4y agoThe Kawai K5 I used to have was also 8096 based.
- Gordonjcp 4y agoIntel 8097 in the Roland W30, and I think also the S50.
- digitailor 4y agoThe later S550 is the unit I was fixing mentioned in another comment, that one was a 8095
- digitailor 4y agoDidn’t know that: hard to believe they managed to pull off additive synthesis on an 8096. That’s impressive I had a later Kawai K5000 which added short PCM samples for attack transients. That thing was crazy, foolishly gave it away more than a decade ago
- pinewurst 4y agoI received a final software update from Kawai and had to open it to install the EPROMs, which is how I saw it. It was a very cool synth - very high quality feeling.
- squarefoot 4y agoI also had a K5000 and was so stupid to sell it over a decade ago; no way to find one again now at less than 5 times that money.
- kapilkchaurasia 4y ago
- dep_b 4y agoThere's also a cool story about somebody fixing some bugs on the Six~Trak and related synthesizers by Sequential that were among the first MIDI synthesizers: http://www.tauntek.com/SixTrackBug.htm http://www.tauntek.com/SixTrackBug.htm Though some bugs are really part of the sound now in my opinion. I bought a DX11 to replace my DX27S but I discovered it doesn't glitch as nice and now I need to keep both.
- criddell 4y agoIf a person wanted to be able to play a little keyboard, would they start with piano lessons or is synthesizer a unique enough instrument that you would start with a synthesizer teacher? Does the world of piano have somebody like Justin Sandercoe from the world of guitar?