P10 and Amplifier Hum (again!) plus Voltage Settings

Two questions if I may.

Amp Hum

My amp is a U.S. made Son of Ampzilla, powered for the U.K. but with a U.S. style plug on a captured power cable. I live in the U.K…

Out of the wall, and out of a Shunyata Hydra, the amp hummed immediately on turning on, this would then settle and disappear, but then sometimes, but not always, return for no obvious reason and it could be quite loud.

When I powered the amp via a power regenerator I got a lower but steady hum which seemed to recede a bit in time but was always there.

Powered via the P10 I also get a similar result as the other power generator, if a little bit quieter.

The hum is at 150Hz (shows up on a speaker frequency response measurement).


Voltage Control

Voltage Out in the P10 was set at 240 volts. The U.K., in common with the rest of the EU, is now supposed to be 230 volts. My Voltage In seems to vary between 232 and 236 volts, THD Out always 0.1%. The manuals of all my gear, where mentioned, say 230 volts.

Should I set the Voltage Out to 230 volts, or perhaps 234 volts (average of Voltage In) to reduce P10 workload? Can this improve sound? Or amp humming for that matter?

I would probably go with 230, it is going to be more in the middle of your range and make it easier on the P10 to perform well for you.

Hum in a system is tough to pin down but if you follow procedures you can get rid of it. There’s a great article in our How To section of the website on finding and fixing hum you might want to look at. Basically the first thing to do is find where the hum’s coming from. So disconnect all inputs to the amp and let it play into the speakers with nothing connected. If there is hum then your amplifier has a problem and needs to be looked at. If not, then it is a ground loop. Follow the instructions to find it.

Good luck!

Many thanks Paul.