[sdiy] Best AVAILABLE OTA for building new designs?

[Chris H. Park]

Nice! Exciting!

Sent from my iPhone

On Aug 12, 2024, at 5:24 AM, David G Dixon via Synth-diy <synth-diy at synth-diy.org> wrote:


I'm actually building my own version of the Korg PS-3100.  I'm calling it the Sketchy Labs DS-3100.  However, mine will have some unique features: Saw, Tri, and (fully PWMable) Pulse waveforms will be blended with faders.  Also, HP, BP, and LP filter responses will be blended with faders.  Finally, two complete and independent ADSR EGs per key (with hold functions), one for the filter and one for the VCA, rather than just one.  Also, the filter ADSR control will be bipolar for weird negative envelope effects.

Each ADSR requires one 2164, the filter and VCA together require one 2164, and the waveform and filter response faders each require one 2164, per key.  That's five 2164s per key, times 48 keys, so there will be 240 2164s just on the voicecards.  I'm presuming another 10 or so on the front panel controls for a total of 250.  It may be slightly more or slightly less.

My worries with this beast are: 1) How much heat will the circuitry generate?  I'm going to install a fan inside the case, but I don't know whether it will be sufficient, particularly since many circuit boards will be stacked about 1 cm apart.  2) Will a 3A+3A power supply be sufficient?  3) Will there be a problem mixing 48 key outputs together?  Will clipping be a problem?  Obviously, all 48 keys will never be played at the same time, but still.

This is a project that I have dreamed of doing ever since I started doing synth DIY.  I know it's stupid and ill advised, but it has been a lot of fun so far, and that's really the whole point.  It's going to take me months to build, and that's also sort of the point.  I've designed the VCOs and the voicecards, and built prototypes that I'm happy with, so once my huge 2164 order arrives, I'll start building.  I still have to design the circuitry downsteam of the voicecards, and figure out the front panel, but I'm not too worried about that.

________________________________
From: Synth-diy [mailto:synth-diy-bounces at synth-diy.org] On Behalf Of Ingo Debus via Synth-diy
Sent: Sunday, August 11, 2024 2:50 AM
To: Synth DIY
Subject: Re: [sdiy] Best AVAILABLE OTA for building new designs?

[CAUTION: Non-UBC Email]


Am 10.08.2024 um 20:48 schrieb Mike Beauchamp <list at mikebeauchamp.com<mailto:list at mikebeauchamp.com>>:

My latest project is going to require about 250 2164 ICs.  That's not a problem given what I'm paying for them.  Yes, in all but the filter
I don't think I'm the only person here interested in hearing more details about your project that uses 250 quad VCA's…

A Hammond B3 style organ, where every key contact is replaced by a VCA? 2*61 keys, 9 contacts per key?

Any other ideas?

Ingo

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