Re: My first valve radio project - Philips 462A
I think the hum is being picked up on the (possibly unshielded) audio cable from the Bluetooth receiver to the PU sockets. This is upstream of the radio's volume control, so will be affected by that.
If so, it could be mitigated by careful routing of the audio cable away from the mains transformer, and / or by using shielded cable for this connection.
__________________
If I have seen further than others, it is because I was standing on a pile of failed experiments.
|