Hoffman Amplifiers Tube Amplifier Forum

Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: musicfixerupper on April 08, 2012, 09:45:09 pm

Title: hum decreases when bass control cranked
Post by: musicfixerupper on April 08, 2012, 09:45:09 pm

Hi, i just finished an ac30 build and there is a hum that goes away when the bass control is turned all the way up. Could this be a ground loop? I followed the hoffman layout and ground scheme.

Title: Re: hum decreases when bass control cranked
Post by: Iannone on April 09, 2012, 01:00:39 pm

Kind of sounds like a bad ground.  First thing I would suggest is resolver the bass control's ground connection, as it might well be a cold joint.

Title: Re: hum decreases when bass control cranked
Post by: archaos on April 09, 2012, 01:22:17 pm

That indeed sounds like a ground loop.

Where are the signal, AC, DC tied to the ground (& how, i.e. a single point or not) ?