The optional initial gain pot? That sort of functionality is okay, as it allows you to compensate for negative CVs on the other inputs, such as when using LFOs that are centered around 0 volts.
The hum would be related to your build. Perhaps using shielded wires on the signal input would help.
Ken
The hum would be related to your build. Perhaps using shielded wires on the signal input would help.
Ken