At 30cm it would fit inside a large letter envelope, anything more would start costing mind you 
I am rather coming round on the notion of a 30cm module, but personally I think anything smaller would be cramped in use - unless you are literally going to go with, 1xVCO â 1xVCF â 1xVCA with 2xAD envelopes or 1xADSR (you might be able to push it to an AD and an ADSR, but again spacing comes up and bites you). I have been trying to lay one of these out for ages now.
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well yeah there is that cramped thing to deal with , one of my pet peeves with euro rack .
1xVCO 1XVCF 1XVCA 1XADSR sounds like a good start .
if possible slider pots on the adsr !
25 to 30 cm
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That module would be relatively cheap and easy to source as well, with the exception of the VCO chips. Everything is built with bog standard parts, itâs all TL072/074âs and (as @analogoutput mentioned a ways up now) a few transistors for the noise circuit. Youâre only expensive parts are going to be the VCO chips (I would choose the SSI2130DAB, which are admittedly ÂŁ20 a go, but so much easier to implement than a 3340, especially if you want PWM without drift) and a vactrol for the LPG.
Conversely, if we went with a straightforward east cost voice you would start having to spend proper money on the VCO (~15ish for a real CEM 3340, plus the additional complexity and price of a precision voltage regulator to get rid of PWM drift as seen in the Fonik TH CEM VCO designs), the VCA (~6 for the dual AS VCA), and the ADSR (another ~6), if not the filter (another ~8ish unless you went with something like an MS20 design), so the pricing of the fancy VCO chips kinda averages out over the two - if price is a concern. You could do it super budget, using a CEM clone for the VCO, ignoring PWM so no need to worry about the regulator, TL072 AD envelopes, an LM13700 based filter and a hack-y transitor VCA, but thatâs not really my thing - Iâd just pay the extra. Of course, we could always design the whole thing with discrete componants, but then it would become much harder to assemble and require extra tools to ensure componants match where required which might put some people off.
Also @devicex, if you want slider pots, that is going to take up a space on the panel about 12cm wide, by about 12-14cm tall once you include the input and output jacks (depending on whether you want to mount both the input and the output on the same edge of the controls), the panel mount ones have 20-24mm (usually) wide fader knobs and a total length behind the panel of about 95mm with a 60mm travel, unless you want to go knobless (which I always think those are pain to use) where you could get it down to maybe 8cm or so wide - so youâre going to end up with a wide panel. Donât let it put you off, I love a good slider (my Klee sequencer is using them, hence knowing the measurements off hand) but they are either fiddly/wobbley bastards (like on say the Befaco Rampage) or big, sturdy and useful (as seen in studio and dj mixers everywhere).
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[ sliders ] yeah just dreaming âŚ
the ss12130 vco ic is L5.99 at Thonk .
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Does that really qualify as âreadily availableâ? It looks good but the DAB version as far as I know exists only in very limited quantities.
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The first run is a limited affair, restock with a full run was expected this month, and although Thonk havenât said when they are expecting them they have said that they are expecting them. I also know that Amazing Synth is carrying them (as it is where I got mine from back when they were first announced). I would assume (like with all silicon chips at the moment) the fabâs are running behind schedule.
Also, if we are having PCBâs made, we can surely put the footprint down for a QFN socket and have the fab do the SMD placement, cos then the chips are super cheap.
$ 9.00 in SMT form at synthcube . [ ss12130 ]
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The DAB variant is the DIP adaptor version, which are being made in lower quantities than the QFN package.
Edit: Which I just realised is DIP Adaptor Board
still a proprietary IC though , but does save a lot of parts .
I worry about using a part as new as this whose future availability seems very much up in the air.
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Itâs far from new, its the re-issue (with improvements) of the chip used in the Prophet 5 (and this version is in the new prophet 5). And if JLC donât Digi-Key have through hole mounted sockets for the QFN 32, then you just push the chip in and away you go.
EDIT: Twasnât the P5, that was the 3340⌠but it was definitely in a Sequential synth⌠the new VCF from the same series as this VCO is in the new P5âs and its original was in the old P5âs
EDIT SOME MORE: It was in the P5, just the Rev 1 & 2 before they replaced it with the CEM3340
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Iâm coming in late here, but would love to help. I can only help with concept and perhaps visuals.
I suggest we keep this within 10cm wide or smaller for a few reasons:
- ease of build
- focused design
- itâs the first collab here
- itâs a common footprint for those of us with wooden rails
I donât think it should be a standard oscillator. Something about it should be spicy. I also think that it shouldnât be too hard to put together using existing circuits. At least not yet.
I think there is a good list of âexpectedâ features already:
- PWM
- FM
- fine tune
- octave switch
With all of that in mind, I think it could include one of these spicy features:
- Detune/Swarm/Unison
- Wave folding
- Sub octave
- Distortion
Perhaps some combination of these could yield an interesting module. Here are a few super rough mocks leaving out some of the expected features for now:
SWARM - The Swarm module could have 2-3 oscillators that can detune with a single knob. Iâm not clear what the wave shape should/would be. Perhaps only saw or square. Iâve never built anything like this.
FOOLâS FOLD - a single oscillator and wave folder combined
BIG SUB - Inspired by @CTorpâs Sub module. If weâre going heavy, it could be fun to add an overdrive/distortion circuit as well.
Ignore the silly names and the layout is just for getting ideas out quickly.
Edit: Mocks in figma. Happy to invite folks to collaborate. Just let me know.
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Subosc is quick and dirty compared to a second osc, but it cannot be detuned because it is based on the first osc frequency. Pretty sure youâd need a distinct oscillator for detune
Also, 20cm width or less in my opinion
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Totally. Thatâs why theyâre separate. I think swarm might be a bit of a pain to build with 2-3 oscillators.
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LOL well we will be at this for a few months trying to refine all the ideas into one module that is fairly easy to build and not to expensive and is 20cm or less or maybe 30cm or ⌠dam I hope we work better than my government works [ U.S. ]
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If itâs just that I think it could easily be fit into 20 cm. The VCA would need no controls other than a switch between ADSR and drone. Four knobs and two jacks for the ADSR, two knobs and 3 jacks (in, out, frequency CV) for the filter, and then thereâs plenty of space left for the VCO. And probably space enough to add more usability, e.g. CV attenuators for the VCF and VCA. It wouldnât be as spacious as Iâd normally like, but again, for a supplemental voice I think thatâd be okay. Itâs not intended to replace full modules.
But itâd be maybe too limited with no LFO, only one EG, no noise.
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yeah a nice simple voice to start with and build from there with future modules ?
but having said that there are a lot of those [ simple vcoâs ] out there so maybe something unique would not be a bad idea ?
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This is why I have been pushing for a west coast design, by all means build a good ole fashioned voice module as well (itâs not like it would be all that hard, especially with the level of experience folks on here have with the EDA software), but surely we have all had enough of that simple VCO/VCF/VCA by now, I mean I have 2 complete three oscillator voices in Kosmo these days, and I am craving a different sound.
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so i can see we are headed for a feature list that we give everyone a week or so to vote on ?