Hum

That Phil guy was round, as usual, and the amp is back on the bench to investigate the source of some mains hum. Nothing too bad but since it's not affected by the gain or volume or whether there's anything plugged in or not, it's worth trying to find out where in the circuit it's being created (or not clamped down or filtered out). Not that we answered that but a nice conversation with ChatGPT suggested some areas to investigate.