Hi Matt,

You are right in assuming that a VCA shouldn't pass any
signal when the gain is completely closed.

A "Gain control", or "Initial Gain" as it's mostly labeled,
is actually nothing more than a variable (through the pot)
DC voltage added to the CV inputs. For instance, if you'd
close the Gain pot, and then add a steady DC signal
(say +8V) to the CV input, you'd achieve the same effect.

Unfortunately "Gain" or "Initial Gain" isn't entirely correct
as a label -- though it's been in use since ehm, forever --
because it doesn't add any gain in most VCA's.
In the case of the 132-2 however, it is possible to have
more than "unity gain" (1 to 1), which can possibly lead
to clipping...

Most VCA's have trimmers on the PCB to trim back the
"CV rejection" and "signal bleedthrough" (*). This should
be set properly in the factory. If that's not the case, then
I guess the module should be re-trimmed at the factory.

(*) I don't know if the 132-3 has preset trimmers.


If you're 'opening' the VCA with a ADSR, make sure that
the Sustain is completely closed and the gate is OFF.
Otherwise you're sending a DC voltage to the VCA,
which could account for the so-called bleedthrough.


_g

On 19 Jan 2011, at 13:24, Matt wrote:

> I've just got my first eurorack modular which I've been using for the
> first time today and have a question regarding the A-132-3 VCA. I
> bought two of these as they seem to offer the most flexibility in a
> small system, but when I patch the VCO directly into the VCA and
> control the amplitude with an A-140 ADSR, even with the gain control
> set to zero, there is a constant bleed-through of the note.
>
> To be honest, I don't completely understand the function of the gain
> control, as I'd have assumed that when set to zero no sound would pass
> through the VCA, and there appeaar to be no manual pages for it. Can
> anyone help
>
> Thanks,
> Matt