Thursday, October 2, 2008

Got a few extra minutes? Why not build your own polysynth?

VSE contributor "adamstan" designed and built his own analog polysynth from scratch. Holy cow. The spirit of DIY lives! Here's some info from the thread on VSE:

"I consider it to be a 'Poor mans Memorymoog' with a little bit of Prophet 5 thrown in . It features:-

  • 5 voices- 2xVCO per voice
  • 3xEG per voice (hardwired to pitch, cutoff and volume)
  • 3xLFO (pitch, cutoff and PWM)
  • Moog ladder VCF
  • Noise source
  • Ring Modulator
  • Patch memory (128 user patches)
  • MIDI
  • Mono mode with selectable note priority (High/Low) and triggering (single/multi) and with portamento
  • Unison with adjustable detuning
  • VCO A offers sawtooth, square and triangle.
  • VCO B offers sawtooth and square waves.

"It's built using only standard off-the-shelf components - no CEM or SSM or similar chips inside - only typical opamps, switches, transistors etc."

"Case (together with keyboard) was salvaged from some crappy 70's combo organ."

It uses a scanned keyboard and microprocessor control of the panel. It has what appears to be a two-line X 80-character backlit LCD display. Adam wrote the firmware himself. Here's a photo (it's the one on the bottom, below the Siel):

The guts:

A close-up of 4 of the voice boards, mounted edge to edge. Note how small they are:

This, needless to say, is one heck of an accomplisment. To build an analog polysynth, at a time when none of the Curtis/SSM component ICs are available any more, and one can barely find a simple OTA -- a great piece of work, absolutely terrific. Adam says it cost him $1600 in parts. VSE contributors are comparing to the $2000 (price via Sweetwater) Prophet 08, and wondering how much it would cost to mass produce. That's a hard question to answer; a company like DSI could certainly get the parts cheaper and realize economies from mass production, but that would be offset by the cost of the labor (Adam's labor was obviously free to himself; he hasn't said how many hours he has into it), and the fact that Adam used a gutted combo organ for the keyboard and case (hence the funky reverse keys in the bottom octave). My back-of-the-envelope calculation is that with the R&D cost already sunk, a rack mount/tabletop version could be manfactured for about $800 and retail would be around $1300.

Here is a link to sound samples, many of them. As I wrote on VSE, the basses and leads are quite Moog-ish, which is no surprise since the synth uses the Moog transistor ladder VCF design, but the pads and strings have more of an Oberheim vibe to me. The ring modulation is a plus and it lets the synth do a lot of things that most vintage polysynths can't do. The synth apparently doesn't have an auto tuning function, as the author mentions that it drifts some, and that can be heard in some of the samples. (It does have variable detuning in unison mode, so don't let the lead samples throw you off.) I personally am not a big fan of synths that don't stay where I put them regarding tuning, but it's what a lot of synthesists want these days, at least from an analog synth. My only other complaint, judging from what I've seen and heard, is that I don't like where the pitch and mod wheels are placed; I'd rather have them to the left of the keyboard. (They are where they are because the recycled combo organ case didn't have room.)

All in all, a brilliant piece of work. I can't help but wonder how much it would cost to get someone like Ken Stone or Bridechamber to mass produce the circuit boards and sell them as kits.

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