PolyKit 16 Polysynth

Thanks,. It’s hard going getting parts for this build, I’ve probably got about a 4-5 week wait now for chips from Germany and Portugal overland as no flights are coming this way. It will give me time to test the 3 boards I have built and possibly start the basics of the rest if it’s sounding good.

I won’t be doing PCB for this but schematics are available for anyone who wants to try.

I estimate that when completed for a 16 voice synth the cost to be around €800-900, but really it’s just an exercise in building and taking my mind off the war.


A lot of interruptions this week with family stuff, power outages and air raid sirens, but I finally managed to finish the DEMUX, dual LFO, noise source and shift register out board. Realized when I finished that I had at least 8 spare outputs on the DEMUX so I could reduce that to 32 channels from 40 as I moved some of the functions to the shift registers and made simple resistor ladders to control the EnvGen8c looping mode.


I’ve got 3 more dual voice cards ready for wiring over the next few days…


First 4 dual filter boards completed. Just awaiting a delivery of AS3364 quad VCA chips so I can populate them and test.


Super Juno coming along nicely, 8 voices complete but I need a new power supply, I’ve got an RQ65B on order from Mouser over 5 days now with no sign of it leaving the warehouse yet…


Given the speed with which you appear to build your synths, and given your grey hair (no offence intended!), I wonder how many synths you have build over the years?


Well first of all the grey hair started around the age of 14, inherited from my father. But at 60 I still have it.

As for building synth, well besides building in my late teens I really haven’t built a synth until about 4 years ago when I got into synth DIY again. I wanted to take a Crumar Trilogy which I owned many years ago and convert it to fully programmable and try to unlock some of the potential to recall LFO settings etc instead of just 8 parameters of the filter and ADSR.

I was also rebuilding a Digisound 80 synth from the bits I still had as a teenager/synth repairer in my earlier years.

Having never used Arduino/Teensy etc this was a steep learning curve for me and I put it on hold.

Instead I turned my attention to a Crumar Stratus to replace the organ divider circuits with some real VCOs, well DCOs in my case. I sort of got this working but it then snowballed into replacing nearly all of the synth with new LFO sections, filters, a programmer etc. This taught me a lot and I spent probably around 2 years on this build with many iterations of programmer, midi converters, filters, VCO/DCO boards etc

This new knowledge allowed me to revisit the Trilogy and accomplish the conversion from manual to fully programmable for all parameters.

Since then I’ve built several things, some work, some need more work. So probably about 5 polysynths and about 3 monosynths in the past 2 years is what I’ve built, along with a few effects, drum machines and other outboard goodies.

Sorry for the long post.


Same age here but started getting grey hair at 18.
8 synths+ in 2 years, is quite a score! You will need quite a bit of space for those I guess.

Yeah that’s the problem, I’m running out of space and since the war started everything is packed away too.

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Yep, space is a problem. I’ve built some 60 eurorack style modules over the last 3 odd years. Most are mounted in one tall rack.

I can still reach the top part of the rack, but clearly I need to expand to the side of it. Mind you, you need a lot of multiples (or very long patch cables) with a setup like this. I’m finishing a hardware vocoder which is contained in another two 19 inch cases, which I plan to install under the B2600 (partially visible to the left of the rack). But I have some 15 PCB’s of different modules waiting to be build queued and every time I build one I get more ideas for new ones, so I will be running out of space again soon I guess.


That’s a big rack, I think my OCD would want it all the same colour, knobs etc. I like uniformity. Just the way I am.

I just completed refurbishment of my Digisound 80 rack and some of the panel prints are different shades so it’s driving me a little crazy.


While building the contents of this rack I learned quite a lot about how to make a module and tried several techniques and approaches, so I ended up with a bit of a mix of styles. But, I’m OCD-free, so I do not mind. And although in retrospect I regret using the green PLA for some of the panels, I will only remake those and leave the rest as they are.

You know the old saying, “If you build it, they will come”. So I’m hoping this is true for my parts. I will get the boards built whilst I’m waiting…


Second DEMUX, noise, dual LFO and shift registers board ready for wiring up.


Completed the second 16 voice DCO card, would have got it completed sooner but the Russians had other plans, 8 hours in the basement awaiting drones and missiles. So 32 DCOs ready to be filtered. I’ve ran out of 14 pin dip sockets, got 200 on order.


Ho man… I dont know what to say.
Hope you and your family can stay safe.
Take care and keep posting awesome synth stuff so we know you are good.

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Thanks, much appreciated, spending a long time hiding in the basement today. Not much soldering going on.


Out of the basement long enough to complete the second digital section of the DCO board. The first 2 RP2040s generate the 16 DCO waveforms and the 3rd generates the 8 gates, 8 CVs and 8 velocity outputs. In theory I could have squeezed it all onto 2 I think as this RP2040 board has one extra pin over the standard Pico. But I want to add the possibility of MIDI channel changes by reading 4 unused pins for the hex 0-15. Still missing lots of chips that are on the way.


Still awesome, I would not have the patients with strip board.

And all whilst under such strenuous conditions.

Thanks for the support, It’s proto board, this would have been twice the size on strip board, even if possible.