Cgs synth

Hi Gerald,
I wonder if the EFM filter input is being overdriven? I have an EFM VCF-1e,
and if I feed an Oakley or MOTM osc to it, I get the same symtom as you
describe. If I attenuate the oscillator outputs before feeding them into the
EFM filter, the resonance works as it should.

Because of the above, I've assumed that the EFM filters I own were designed
to be used with standard line level signals, but I could be wrong.

Andrew Sanchez

On 10/3/05, Gerald Stevens <logo64@...> wrote:
>
> 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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