Hum gone...Why does this work?
Moderators: pompeiisneaks, Colossal
Hum gone...Why does this work?
I had a bit of hum in my just finished HRM that becomes audible when the amp is being pushed a little. I was not really concerned about it, but while fooling with some other stuff, I remembered someone on this forum said their hum levels went down when they connected the relay supply return to the main ground. I tried it and it was dramatic. I get almost no hum now. Even at full volume the hiss is louder than the hum. This is way, way louder than I would ever consider playing. Why does this work??? I consider the relay circuit completely isolated from the signal path and cannot see how connecting them together would make the hum go away. I would expect the opposite to happen. BTW, I use a bridge recto on the relay so the center tap is not used and is not connected to anything. I just connected the relay power supply return to my ground buss. Also, I am not floating my heaters, just put the heater center tap straight to the ground buss.
Re: Hum gone...Why does this work?
Tonegeek,
That's interesting. I have a non HRM amp that heisthl built for me from an old Music Man RD-50. When I engaged the OD, I noticed a hum. When I would touch the outside of the plug that fed my relay footswitch, I noticed a big decrease in hum. I then tested connecting the corresponding lead on the footswitch jack to ground. Voila! Super quiet. I hope someone with more tech savvy than I have will chime in on this.
That's interesting. I have a non HRM amp that heisthl built for me from an old Music Man RD-50. When I engaged the OD, I noticed a hum. When I would touch the outside of the plug that fed my relay footswitch, I noticed a big decrease in hum. I then tested connecting the corresponding lead on the footswitch jack to ground. Voila! Super quiet. I hope someone with more tech savvy than I have will chime in on this.