[sdiy] Best AVAILABLE OTA for building new designs?

[Mattias Rickardsson]

On Sun, 11 Aug 2024 at 22:15, 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.
>

Hoo-haa!


> ...
> Each ADSR requires one 2164
>

Wouldn't one VCA per envelope generator be enough? Depends on the design,
of course.


> ...
> My worries with this beast are: 1) How much heat will the circuitry
> generate?
>

The majority of the power in a synth circuit is often burnt in the ICs just
by having them powered up, so try to estimate the number of them and their
supply voltage. Perhaps you use a lot of transistors instead, and perhaps
you use TL064 or other low-power op-amps - then things might be a bit
different and the above estimations less realistic.


>  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.
>

Stack them vertically and also let air pass through the casing, and it will
be fine and cosy. :-)


> 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.
>

Gainstaging a synth with lots of voices is a nontrivial problem. But at
least it's just one gain factor that needs to be decided upon..


> 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.
>

Fun times! :-D

/mr
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