[sdiy] SSM2164 VCA

[Scott Juskiw]

Why use a switch at all? Why not use a summing amp (or even just a pot) to allow both exponential and linear at the same time? Looks like it wouldn't be too difficult to do with Marc's circuit. I built some VCAs using an SSM2022 chip that allows both linear and exponential CVs at the same time. Sometimes I'll use 60% linear 40% exponential, sometimes 80% linear and 20% exponential, depends on the patch.

On 2010-03-15, at 4:35 AM, David G. Dixon wrote:

> The only problem with the circuit, as Phillip Gallo pointed out to me the
> other day, is that when the log/linear switch is actually being switched,
> there is a very short time (< 1 ms) during which the linearizing opamp is an
> open-loop integrator, which may temporarily send the amplifying VCA to
> maximum gain.  This had never caused a problem for me, because I generally
> do not flip the log/linear switch during use.  It's either on one setting or
> the other.  However, if the switch is flipped when the VCA is in a high gain
> setting, it can sometimes give an annoying "pop".  I will probably try
> limiting the voltage from the linearizing opamp to some maximum negative
> value with a diode clamp to limit the VCA gain during switching.  Other than
> that minor detail, the VCA is a dream to use.  I'll send you the "package".