Doepfer

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