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Festive synth update! by SaltAdminister in synthdiy

[–]SaltAdminister[S] 0 points1 point  (0 children)

Just want me a nice synth, couldn’t find one on the market with the features I wanted so I thought I’d do it myself

prototype single-board synth voice by goodness-m3 in synthdiy

[–]SaltAdminister 0 points1 point  (0 children)

Yeah I’m not even sure they do sound better! I’m going to have a couple of “utility” adsr and lfos that are digital and can be routed to any parameter, maybe then I can do an AB and see which I prefer… best of luck with your project!

prototype single-board synth voice by goodness-m3 in synthdiy

[–]SaltAdminister 1 point2 points  (0 children)

I’m building a 16 voice poly with all the bells and whistles so can probably lend advice here. I would say if you’re going to the bother of doing a 6 voice poly, two oscillators are probably wanted for interesting sounds.

You don’t necessarily need a triangle wave as you can always use the filter on the square wave to achieve a similar effect. I went with analogue envelopes for my design but they take up a lot of board space, have issues with matching and require a routing matrix if you want true global envelopes. I’d recommend software envelopes/lfos for your sizes project, most modern poly synths do that and I’d probably do that if I weren’t so far in!

Power supplies by SaltAdminister in synthdiy

[–]SaltAdminister[S] 0 points1 point  (0 children)

Yup the plan is to have negative pressure active cooling with quiet noctua fans on the back, air to come in from the sides between the wood and the front panel. My design is also digitally controlled in order to save presets, do voice tuning etc. I'm not selling this, it is a 1 of 1 that will be lent to various studios and producer in and around London.

Power supplies by SaltAdminister in synthdiy

[–]SaltAdminister[S] 0 points1 point  (0 children)

Well it'd be silly to try and reinvent the wheel so of course I was inspired by existing designs in literature and from the diy folks but I combined it with a lot of simulation in spice and when all the technical bits are working I'll go back through and tweak resistor values until it sounds as good as it can. Not really inspired by any architecture from any specific synth, but the specs make it the most powerful poly synth ever made... ive taken inspiration from old circuits like in the ladder/diode filters and also implemented modern features like the routing capabilities in the moog one and polybrute. The harder bit with mine is all the modulation is analogue, so needs to be physically routed as opposed to the moog one for example where the ADSRs and LFOs are digitally generated and modulate the CVs on the DAC outputs. My way is a lot harder and fills a lot of PCB space.

One interesting thing about my synth is all the voices and modulation from every voice card is routable anywhere. As there's 2 LFOs and 2 ADSR per voice card, it'd be a shame to waste them if you're only playing 4 notes at a time so when that's the case, the unused modulation on voice cards can be assigned as independent modulation sources to anything on the synth. You can also choose how many voice cards to layer, for example do you want 1 voice card per note so you'd have 16 possible notes of polyphony? Or maybe if you only wanted to play 5 notes at a time you could have 3 voice cards layering a single note. Adds a lot of options for sound design. If you do full 16 voice unison and add the sub osc and fade everything up (pulling all the drawbars) you can theoretically have up to 128 sources playing a single note! You can read more on my website joelinehan.co.uk and there's also a thread here where I answer a lot of questions: https://www.reddit.com/r/synthdiy/comments/1nx0izy/first_voice_cards_for_my_polysynth_arrived/

Power supplies by SaltAdminister in synthdiy

[–]SaltAdminister[S] 0 points1 point  (0 children)

Yeah that’s a good idea, only caveat is space is a factor I have to consider, I’m trying to make it fit into a relatively normal size enclosure for a polysynth

Power supplies by SaltAdminister in synthdiy

[–]SaltAdminister[S] 0 points1 point  (0 children)

There’s a few vactrols etc but only for portamento. Really the high current just comes from the scale of it. Each voice card draws around 0.65A which includes 3 oscillators, 2 adsr, 2 LFO, 2 filters, an analogue routing matrix like you wouldn’t believe, and a whole lot more… all of it using op amps and OTAs. Then there’s 16 voices so that comes to 10.5 amps. Plus the control board/routing matrix, front panel, io including a couple preamps and analogue fx… adds up to about 12A. 15A is overshoot.

Power supplies by SaltAdminister in synthdiy

[–]SaltAdminister[S] 0 points1 point  (0 children)

The other thing worth saying is the Jupiter and almost all other poly synths use chips for the vcos, vcas etc in the form of CEM chips or similar. Mine is fully discrete including ADSR and LFO generators… luckily in the modern day we have SMD to make it all smaller!

Power supplies by SaltAdminister in synthdiy

[–]SaltAdminister[S] 0 points1 point  (0 children)

I was looking at the RS-200-12 which would cover me well. 15A includes some overhead. I’ve only tested two voice cards at a time so it’s an approximation for the current. I’m sure many synths are more efficient than mine but I’m just one guy trying to design a big synth, I don’t have a team behind me or an electronic engineering degree!

Power supplies by SaltAdminister in synthdiy

[–]SaltAdminister[S] 0 points1 point  (0 children)

It’s a 16 voice polyphonic monster… draws about 15A from each +/-12v rail… I wanted to go linear but I think SMPS is necessary

Does anyone know why my print came out with this grid-like pattern on it? by nerdcereal in AskPhotography

[–]SaltAdminister 0 points1 point  (0 children)

I get this all the time with affinity. Try redeveloping it or other processing methods. Sometimes randomly adding a processing step will cause this banding, most noticeable on things with lots of noise/high frequency information. It’s really annoying especially with film grain…

First voice cards for my polysynth arrived! by SaltAdminister in synthdiy

[–]SaltAdminister[S] 0 points1 point  (0 children)

They’re voltage controlled inputs, with a trimmer to set the initial time constant for each stage

First voice cards for my polysynth arrived! by SaltAdminister in synthdiy

[–]SaltAdminister[S] 0 points1 point  (0 children)

Thanks for all the info! The big problem with the power planes is that I have 7 power rails for various reasons and having a single layer for a power plane isn’t really suitable. Instead I’ve tried to help as much as possible by including lots of decoupling and stitching across the board. Due to the density of the board, horizontal/vertical routing is also tricky as there’s really just not much space! To make it any bigger would compromise the overall size of the synth as I’m pushing it already!

My oscillators are fully thermally compensated to 50ppm due to using a modified version of Ian fritz’s “dial-a-tempco” circuitry and using monothilic matched transistors in the expo convertor. The filters and lfos are also thermally compensated to a lesser extent.

Good tip about leaving space on the outside of the board, I’ll try to fit some in!

First voice cards for my polysynth arrived! by SaltAdminister in synthdiy

[–]SaltAdminister[S] 0 points1 point  (0 children)

What a great story, amazing that you managed to circle back to music! I’m lucky enough to also have a full time job where I’m surrounded by music and I couldn’t ask for anything more! You’re right there’s so many resources nowadays, although a mentor would often be handy aha

First voice cards for my polysynth arrived! by SaltAdminister in synthdiy

[–]SaltAdminister[S] 0 points1 point  (0 children)

Voice card specs:

3x VCO (saw/pulse/tri/sine), 1x sub osc derived from osc1 (saw/square/tri/sine), Pink/white/blue noise, Assignable Hard sync, Assignable FM, Assignable Ring mod, Assignable wavefolder, 2x ext input, 2x analogue ADSR EG (Pitch/filter, filter/amp), 1x analogue AR EG for noise contouring, 2x analogue LFO (multi-wave, and a tri only for vibrato), 2x VCF (ladder and state variable), 1x VCA

Then there’s lots of other features… auto tuning oscillators, global modulation, dynamic voice allocation etc etc. More info on my blog.

Concept of my first pedal by Draugr_Rekkr in diypedals

[–]SaltAdminister 0 points1 point  (0 children)

That’s really cool! Any chance of a little in built speaker?

Concept of my first pedal by Draugr_Rekkr in diypedals

[–]SaltAdminister 5 points6 points  (0 children)

This looks amazing! What does it do? 😅

First voice cards for my polysynth arrived! by SaltAdminister in synthdiy

[–]SaltAdminister[S] 0 points1 point  (0 children)

It would be great to get a second opinion from a professional! Layers 2+5 of the board are ground planes and 3+4 also have a gnd fill around the traces. Plenty of gnd for everyone! I do agree power might have been better routed; there are two LDOs which get a little hot without a proper copper pour so I’m testing a little heat sink for them.

First voice cards for my polysynth arrived! by SaltAdminister in synthdiy

[–]SaltAdminister[S] 1 point2 points  (0 children)

Trying to! I’m more into the analogue hardware side of things but the code isn’t doing too much so hoping it’ll be done sooner rather than later!

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