[sdiy] Ken Stone Tube VCA question

[Paul Perry]

Tubes - or valves as we Anglophones call them - normally operate with the
control grid a few volts negative with respect to the cathode.
The current flowing through the cathode resistor R7 ensues that it is so. ;D

And the cap smoothes out any AC voltages (from the varying cathode current)
that would otherwise manifest as negative feedback.

paul perry  (born pre-transistor) Melbourne Australia