[AH] Doepfer 3340 search

[>>>marjan<<<]

> > One must point out that only one of the Doepfer VCOs uses the CEM chips
> > (the A-111). The other audio range VCO they sell does not (the A-110).
> 
> But this VCO is woefully underpowered. It is missing many options
> available only on the 3340 version, and I hear it drifts.. Yuck!
> 

There's online schematic for A-110. You can see it's Moog Prodigy VCO
clone, but it looks also to me that it's intentionally made to have
bad performance (in comparison to CEM one) and that with little redesign
it can be much better. It uses quad opamap chips :( and instead of
comparitor it uses opamp for switching transistor (instead JFET),
and some too simplistic tri (two inverting transistors summed if I
remember correctly) and sine waveshapers (classic two antiparallel
diodes + buffer), and uses standard heated 3046 chip (method some of
you dislike, but I find it OK for me as I can't get tempcos).
This method isn't such "drifty", so I think something is miscalculated
in control loop or heater or above mentioned opamp and transistor 
have more affect than expected (bad analogue dept as someone noticed).
It could used some AD opamps and fast comps. 
I bet Tomg's vco4 does better job than a-110 (being same prodigy vco).
Somebody could point them to some designs some list members made
of say upgraded asm-1 vcos (not to copy, just for info).
This vco still looks like it's made "Low-end" on purpose.
There are CEM/tempco/heated/linear/diff. compensation, vco designs
and they made bad decision (running it without stocks of cem chips) 



marjan