[sdiy] AC coupling on inputs/outputs.

[David G. Dixon]

> I think I understand why this is often done, but wonder how useful it
> really is in a modular. I have some EFM VCA PC boards that offer
> independent DC and an AC signal paths on inputs and outputs. Is there
> any particular reason why a VCA might benefit from AC coupling, rather
> than simple DC-capable Inputs/outputs?

Apparently, gating an audio signal with a significant DC level leads to CV
bleedthrough, causing a nasty popping sound.  However, if your system
generates audio signals without dc bias, then I can't see the need for it.
My VCAs don't have this option, and I haven't missed it.
 
> I'm re-panelling several modules, and wonder whether the extra
> sockets/switches are worth including....

For VCAs I would definitely recommend separate input level and CV bias
knobs.  Many argue against them, saying they're redundant, but I can assure
you that they are not.  I use the input attenuator as an overall volume
control, and play the CV strength and CV bias knobs against each other for
various effects.  The CV bias knob also allows you to use otherwise
inappropriate signals (such as triangle waves) as VCA control signals by
lifting them above 0V.  Email me for details if you're interested.