[sdiy] CMOS Switch as VCA?

[Magnus Danielson]

Scott Nordlund wrote:
> Forgive the dumbness of the question, but has anyone tried using a standard CMOS switch (4016/4066) as a "sort of" VCA?  I mean with an actual linear CV input, not using PWM.  I haven't tried it and I've never seen any reference to it, but I can picture it almost working, though probably not in an optimal kind of way.  At least it wouldn't have the CV feedthrough problems of a single transistor VCA....
> 
> Any ideas?

The Sennheiser VSM-201 vocoder uses CMOS switches as VCAs through PWM.

> I've also seen a completely bizarre 4049/4069 hex-VCA that uses the power pins as the output, but this has the obvious disadvantage that all the signals are mixed together.

The 4069UB is cheap. Use several if it bothers you. Those VCAs uses the 
fact that a FET transistor can be made into a linearised 
voltage-controlled resistor.

The internal logic of 4016 or 4066 does not allow similar tricks. You 
are essentially bust on that quest. I will look again, but I am pretty sure.

Cheers,
Magnus