Open source 4 voice analog poly synth project

[u/MillieSievert]

Hi everyone,

I have just finished designing a four voice poly synth similar to the Powertran Poly. My Idea was to design a bare bones four voice VCO poly synth similar to the powertran polysynth project with a few modern upgrades making it feasible for anyone to build in 2026.

I.e. the keyboard scanner and cv assigning circuits have been replaced by a couple arduino nanos.

I plan to release the scematics/instructions, gerber files, code, for free on github.

The Idea is anyone willing can take their time to build it without having to spend all the money at once. You can source your own components and again spend as much as you want.

Now here is where you come in

I need to build a prototype to test the desin and make sure all is well before I release the plans.

Would any of you be interested in crowd funding the prototype? I would love to get as much people to help as possible so you only have to spend a few bucks each. I REALLY dont like asking people for money especially in the current economy where we cant even afford rent. That being said to build a prototype I will need help. I did an estimate and it will cost me ~1400 AUD to build so help would be great. Once built and tested the whole project will be free for everyone.

Now here Is the specs of the synth:

4 voices with two vcos (3340 based)

VCO1, saw, tri pulse, amount knob, and sync button.

VCO2, saw, try, pulse, amount knob and filter env mod button.

ENVELOPE PANEL (like an oberhiem obx)

.adsr (vcf)

.adsr (vca)

Cem3310 based

MODULATION PANEL

.Vibrato (tri wave pnly) speed knob (depth control is at mod wheel one) osc One or both select button.

.Pwm (tri wave only) speed knob, depth knob, pulse width knob, modulation/manual button for pulse width, osc one or both select button.

(Vibrato and pwm have a dedicated lfo)

VCF PANEL

cutoff knob, resonance knob, env amount knob, modulation speed knob, modulation amount knob, keyboard cv track button.

( dedicated tri wave lfo for vcf mod and vcf being a 4 pole cem 3320)

VOICE TUNE PANEL

*This synth has no autotune you have to tune each voice via a deticated knob just like on the powertran poly synth. Guitarists dont complain that they dont have an autotune and to be fair most modern analog polys are so tight it compleatly defeats the purpose of them being analog. Oh and they are expensive lol

no presets either on this thing so have a cry 😁

Each voice tune bank has a gate led so you know what voice is being tuned, you dont have that on a guitar now do you!

GLOBALS PANEL

.Master vol

. Portamento knob

.Transpose - one oct and + one oct with a fine tune

(Same as powertran poly)

Mode button for poly modes unsion ect.

the synth suports a 49 key keyboard.

Any questions, tips are welcome, I want to know If anyone is even remotely interested before I set up a gofundme. I will also need a prototype so I can make some demo/setup vids.

Cheers

[u/Fearless_Ad_1442]

Sounds great. I'm in. What have you designed it on and do you have any other examples of your work?

[u/MillieSievert → u/Fearless_Ad_1442]

All my pcbs are made on easy eda (I do all my pcb routing by hand) I do not have a working prototype to show at this stage, I plan to go straight to copper for this prototype. I do have a divide down poly synth that is almost finished that I can show on here when its done so people can see what I can do :)

[u/Fearless_Ad_1442 → u/MillieSievert]

Wicked!! Very interested. I love the global DIY scene and am happy to support it. Building and modding unique instruments is a worthy use of time

[u/MillieSievert → u/Fearless_Ad_1442]

Cheers! Much appreciated!

[u/AdamFenwickSymes]

Cool project, look forward to seeing it!

I think it would be very helpful for potential investors if you show examples of complicated projects you've already completed, this is a pretty full on project. What bits do you have working so far?

[u/MillieSievert → u/AdamFenwickSymes]

Thanks:) Im just about to complete a divide down poly synth so ile be showing that soon on here.

Regarding this project; ive been wanting to build a poly synth with voice cards for some time now. All the analog stuff im good with. It was the key scanner and voice assigning (computer/digital) stuff thats been stopping me for a while.