ho hum...............

[zappa 100]

i have a persistent and annoying hum emanating from my alpha 9 power amp ,through the speakers. the volume of the hum stays the same regardless of volume control position. the mains block is plugged into a double socket . in the other side of the socket ,a small lamp is plugged in. when i either switch this lamp on or off at the socket ,the hum disappears, only to return about 1 and half to 2 minutes later. can anyone explain why this should happen and if it can shed any light on to the source of the hum?

 

[Tibor]

The electromagnetic field, I suppose.

 

[Andrew Everard]

Energy-saving lightbulb, by any chance? Or a low-voltage halogen lamp? They can be very noisy in electrical terms...

 

[Anonymous]

[quote user="Andrew Everard"]
Energy-saving lightbulb, by any chance? Or a low-voltage halogen lamp? They can be very noisy in electrical terms...
[/quote]

Yes, but if it went after he turned it off surely this cannot be the problem. Perhaps try swapping round the plugs around, it may be a dodgey socket.

 

[JoelSim]

Why don't you try a shielded mains cable?

 

[Anonymous]

[quote user="JoelSim"]Why don't you try a shielded mains cable?[/quote]

A very viable point...

 

[Anonymous]

My mum's Quad 405 went the same way too...but it did take 28 years of use!