Diy helph


Hi,
Ive just put together an amp / preamp combo. Every thing sounds great but it has an audible hum when the amps input cables are connected to the preamps outs, the hum is not effected with the volume, its a set volume.
The weird thing is if i connect either a left or right channel only via the cable theres no hum?
Its only when both channels are connected.
Anyone got any ideas?
Regards
Mike
milo66
Nice one fuzztone, 
assuming that your connection is with rca's then most propably a ground is touching signal. Have you checked both cables or just one? What happens if you rock the rca's at pre's output or power's input while both cables are connected? Unscrew top covers-units off mains- and check that rca's at both units have a tight fit.
You can use a voltmeter to check any kind of shorting if you wish.
G
At first I thought that the title of the thread was in a different language.
Have you tried interchanging the cables? I had a situation where one of my cables potentially had damaged shielding and would catch radio interference when connected to my turntable.
have you try a ferrite ring on power cord of preamp and or amp close to the unit
Nice one roxy54
All you can do is try every combo and it still might not go away. Move the pieces and IC around. I have a bag of iso transformers I try..
Start with in between.
Lotso luck.