Cgs synth

Something odd is going on. The CGS60 gives a 20x gain, and is very high
impedance - around 150k. If you are only getting a fraction of a gain, there
is something seriously wrong with what's driving it. Add a CA3140 or maybe a
TL071 as a non-inverting voltage follower/buffer to lower your output impedance.

Ken

>Question about the cgs60 stomp box adapter and using it before a filter.
> I built a modular C64 SID synth that is a lovely beast, with CV ins and
>outs, and I bought a cgs60 to bring its output up to PAIA/Blacet levels.
>This works fine - a 3 Vp-p is brought up to about 5Vp-p, nice and clean, and
>you can hear the difference if you route it through a VCA. When I run this
>through an EFM VCF-2F moog filter, the filter frequency works, but the
>resonance control no longer works. This filter uses a LM13700 OTA, and it
>has been noted that its output isn't buffered properly... maybe that is
>contributing to the problem. Running the amplifed SID signal through a PAIA
>9730 multimode filter doesn't work very well either ... but is harder to
>characterize. It just seems that the filter's range isn't quite as wide, and
>the cuttoff not so severe. Is it possible that these filters require more
>current than the op-amp in the cgs60 can give? My PAIA oscillators work
>perfectly through both filters. It is a little odd that not all 5V signals
>were created equal. Maybe I'm having impedance matching problems?
> -gerald
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>The CGS Modular Synth home page: http://www.cgs.synth.net/
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>Yahoo! Groups Links
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_______________________________________________________________________
Ken Stone sasami@... or sasami@...
Modular Synth PCBs for sale <http://www.blaze.net.au/~sasami/synth/>
Australian Miniature Horses & Ponies <http://www.blaze.net.au/~sasami/>