Yes, full SMD.
I thought more of “porting” it to “true” Kosmo, leaving out what is not needed/wanted in a “voice”.
The sequencer, the noise, S&H, etc…
I was thinking about this; how about a sort of ‘solderable patch bay’ where folks can pick and choose how they’d like the module to be routed. This can of course, be overridden by patching with cables externally.
Also, a minor technicality, but (imho) quite important; do we want jack sockets near their corresponding knobs on the module(think Sam’s VCAs) or all at the bottom(1222 VCO)? I think aesthetically, the former, but functionally it is easiest to have all the patch cables out of the way.
Probably too early to decide now but food for thought 
.
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The whole ‘route it yourself’ is pretty much already there in a certain respect. Since I envisioned those modules to be routed via the output jacks switch normal solder tabs, you could simply wire them wherever you like, leaving the normal routing off the board entirely. The issue then comes with how you would mark it on the front panel (assuming that we are doing a pre-fabbed front panel so it looks nice and slick).
Also I am decidedly in the ‘Jacks by their functions’ camp (as pictured) rather than ‘All jacks at the bottom’ for combined modules, for me at least it just makes it so much easier to understand. Although I do like the Mother32-style patchbay for patching convenience, its still a pig to track down exactly the jack your looking for and it would need tiny cables or it would just look insane.
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my 2 cents . would be nice to stay away from the digital , pic’s or arduino type stuff for now .
I like the idea of two different modules east coast , west coast style both have their merits and it would be a bit much to cram all that goodness into one module . I like the idea of using switching jacks for normalized patches between a modules components simple and space saving .
the examples you guys have so far look good .
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Link? The only one I could find is this:
and it’s a little outside my budget for this. (Also they only have 12.)
Maybe the DAB version really is going to become a lot more available but at this point it seems to me too iffy to count on. It also costs $20 so that’s $40 right there for the West Coast design.
Sam claims the 3340’s stability problem can be fixed without a regulated -5 V but I’m not sure I buy it without more testing. Of course you can skip the on board PWM and use a comparator but then you start to lose the advantages of a VCO on a chip. It still may be the best option.
But I’d not be in too big a hurry to rule out an op amp VCO. For matched transistors you have a number of options:
- SOIC package — really not that hard to solder
- DIP package NOS available e.g. from SynthCube ($$)
- Self matched discrete transistor pair — cheap, not hard to do, requires only a voltmeter and a small breadboard circuit
- Matched discrete transistor pair available from Thonk — still pretty cheap, easiest option
As with the MFOS VCO the design could allow for the user to choose any of the above.
PTC (tempco) is still a bit of a stumbling block, SynthCube and Modular Addict and presumably Thonk still have them but for how long? But the Polykit design uses an NTC which appears to be cheap and readily available. I don’t know why these haven’t been used more and maybe there’s some good reason, but maybe it’s just cargo cult. If the NTC design works then it’s probably the way to go for a non 3340/SSI2130 design.
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Yeah, the one I have been looking at is 2x7 2x9 not 4x8. That’s gonna be a stumbling block on the affordability front for some. But honestly, to me at least, £40 on thru-zero VCO chips is nothing - especially considering the price of built modules those kind of chips come in. But each to their own, not everyone is going to have the same level of disposable income. The rest of the west cost design is going to be pretty cheap as far as parts go though which in my opinion balances it out, whereas if you go all CEM on the East Coast it’s going to work out similar in terms of custom chips, but it can be done much cheaper obviously.
As for Thonk and tempco resistors, they very occasionally have them in. It’s not by any means a done deal.
If that’s this one 8432-11B1-RK-TP 3M | Connectors, Interconnects | DigiKey then that’s a PLCC socket, not QFN. A much nicer price, but not usable for us!
Yeah, I had just done a cursory google search to make sure it was a thing you could do, but ah well.
I did a little looking and found a couple of discussions of using NTCs:
https://www.schmitzbits.de/expo_tutorial/
(last paragraph)
(in the context of a filter that needs more than typical temperature stability)
tl;dr:
(Schmitz)
The price is even lower, and these are available everywhere. I have done some comparisons between Pt-resistor, KTY, NTC and an “ideal” compensation, and I found that the performance for all three is comparable within the most interesting range of operation.
(Skala)
Overall, I think the NTC thermistor circuit is quite acceptable for an analog synth filter, and in practice with the prototypes I’ve built and tested, it does seem to keep the frequencies about as stable as I want them to be.
So there you are… sounds to me like it just makes good sense to use NTCs rather than tempcos in new designs. Not that I don’t have about five tempcos in my stash, but that’s just me.
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Just realized, if we want to go down the all-in-one chip route, but not use a 3340, we could use the £5.25 SSI2131 - no Sine out, no onboard mixer and no Thru-Zero FM but still a rock solid Tri-Core VCO and this one is SOP-16 so it would make a nice ‘First Surface Mount Componant’ project. I had forgotten all about the 2130’s little brother… We could also make the almost entire voice out of their chips, as they have a nice moog-style ladder filter and VCA which are also SOP-16 and cheap, the three together would cost about £15 total, just add EG’s (so ~£5 for a AS3310 all analog ADSR and then an opamp based AD and the East Coast voice is golden). We would also have spare VCA’s (as that SSI VCA is a quad) so we could have some fun routing possibilities for things like voltage control over LFO amounts or FM inputs.
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Just my two cents on the discussion going on:
- Through-Zero FM would be extremely cool and would greatly expand Kosmo voicing options and I’d be willing to pay a premium for it
- I would expect a whole-voice module to be more expensive than a single-use one
- I am anti-surface mount
- I am anti-hand-matched-bits
- I still like the VCDO
- I like jacks at the bottom, I think it makes the machine more playable without all the cables in the way of everything
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tuning trimmers accessible on the front is a nice option .
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Yeah, the Thru-Zero VCO’s are not cheap, which really doesn’t lend itself to this particular project since there is a need for quite a few different parts and blowing more than half the project budget on the VCO’s chips, before even considering the associated parts to make them work, is probably not wise. I hadn’t noticed at first there was a desired componant total price in the OP.
With those Thru Zero VCO’s discussed above you can either surface mount them with a QFN package which is cheap but far from easy (for a while I was under the impression we might be able to manage this in a socketed solution, but this turned out not to be the case), or pay £20 (or your local equivalent) to get them on a DIP-32 adaptor board - which may or may not become easilly available, as so far SSI have only put out one batch of the prototyping board. Now I have two of these prototyping chips, so I have a vested interest in using them in something fun/cool, however, they may be better suited to a dedicated West Coast VCO module than this voice, which is something I am actively working on at present. Since the non-DIY versions of these kinds of modules are always massively expensive just having them in the format would be a bit of a coup, even at a premium price point for Kosmo module build.
I am also, in general, against surface mount. It can be a fiddly pain in the arse and often doesn’t come with any real advantages given that the Kosmo format is so large that most modules would easilly accomodate their thru-hole equivilants. Sometimes, however, they do serve a purpose other than miniaturization. The SOP-16’s I mentioned above are, basically, the only way of getting those chips, as they are not made in a DIP package. Soldering them is also not too bad, because the lead spacing on them means that you can actually hand solder them with a fine tip iron, rather than having to use solder paste and stencils with a hot air soldering solution or drag soldering etc. They are also pretty cheap, especially compared to genuine CEM parts, coming in at the same price as the AS clones. Then specifically with that VCF it’s a way of getting a Moog-y ladder filter without either hand matching transistors, paying a whopping premium to have them matched for you or just plain old buying one from Moog (in the past I have done all three in order to get that sound). Granted you could probably limit the voice board to only use two of them, one for the VCO and one for the VCF and only use a dual AS3360 VCA to keep the surface mount part count down as low as possible.
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so it would seem we are leaning a little toward more then basic build / price point in favor of something more unique . which seems a good way to go , there are already dozens of basic vco’s out there . still would like to steer clear of something that has to be programed or ic’s that are going to be rare .
Just playing devil’s advocate… if we really wanted to use the 2130 chip we could make our own dip adapter and sell them with the chip pre-soldered to it. Just means someone with a steady hand would have to manufacture them for kit use.
I don’t have a horse in this. I’m going to be happy to build whatever the CAKE turns out to be and slide it into our rack. 
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As a sidenote, I would LOVE to have @heckseven get a function generator out of this project so that I can buy his Maths 
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so much yes!!!
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I just stumbled upon these qfn32 to dip adapter boards:
[1,50€ 17% OFF]QFN32 QFP32 Converter SMD To DIP Adapter PCB Universal Board Module Board from Electronic Components & Supplies on banggood
Is this usable for the ssi2130 chips?
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Someone would still have to solder the QFN to the board. In which case might as well just solder it to the module PCB.
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except that if we have someone who is good at that they can make the ssi2130 accessible to anyone who is willing to pay for it.
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