WAD HD83 hum

[buddam]

Hi all

just bought a HD83 in Maplin case, with loads of upgrades and extra components (including 'upgraded' trafos). It has quite a hum - which doesn't increase as volume increases. If the power amp is switched on the hum comes through the speakers, but disappears when the HD83 is disconnected from the mains, but not when it is simply switched off while still plugged in.

Have now moved the HD83 4 ft away from the rest of the system, plugged into a second socket board, and using longI/Cs the problem persists. Through both headphones and speakers the hum is worse on the right channel. So, it seems that trafo hum is being fed back into the mains and is being picked up on the right channel of the power amp.

Any ideas gratefully explored

Adrian

[Little Mick]

First part sounds like an earth loop to me.

Second could be coupling via the transformer (physical) have you tried moving it or altering its orientation.


Regards

[Tony Moore]

My HD83 always buzzes when first switched on until the valves warm up then it's very, very quiet.

I just wonder if that's connected in some way to your problem?

Cheers,
Tony

[buddam]

Thanks Mick and Tony

I have reoriented it, to no avail. Think like Mick that it's an earth loop. Will have to check all earthing arrangements (more an art than a science & there's loads of earthing connections)

Adrian