Odd hum problem

[woody]

I have an Antique Sound Lab MG-s115 that has a strange hum
problem. This amp has a built in volumn controle. When the volumn controle is at 1/2 rotation I have maxium hum, turn it
up louder and the hum decreases ! Any idea what would cause
this?

Thanks,
Woody

 

[anatech]

Hi Woody,
The volume control presents the maximum impedance to the input circuit around 1/2 resistance. A load on the input (source like a CD or buffered preamp) would reduce or eliminate this.
You can also try shielding the volume control and leads. Also watch where your input wires run from the jack to where ever.
-Chris

 

[woody]

Thanks , that was the problem. I just couldn`t see it.

Woody