RGR Model 4 Pre Amp ....HUM QUESTION


When RGR Pre- Amp tone button is pressed IN, this Unit is quiet / NO HUM.

However, when tone button is OUT, I get a HUM.

The hum disappears when pressed IN.

Any thoughts about this problem ?

Thanks

rocky1313

Which way is on? Are the tone controls turned way up when you engage the button? If they are turned up, set them to 0 or the flat position. Just a thought.

How long have you had this preamp? Have you made any power amplifier or other  changes? These are fairly old and have been known to have some cold solder issues.