The Amp Garage

My previous thread.. http://ampgarage.com/forum/viewtopic.php?t=12110&highlight=hum I have done a couple of things to try and fix this hum problem. #1 I took out my input selector switch and I took out the hum balance pot so everything is original to specifications. The next thing I did I went to th...

I am running my variac up to 100% since I modified the power supply to get my main voltages right. As far as the heater voltages are at 100% measuring ac across the two legs of the hum control pot I get 7.8 volts, if I measure from each leg to ground I get 5.6 volts. Secondly, I measured the resista...

Yeah, I moved around all my filament wiring and it didn't make any difference..

Alexo wrote:Those freewheelin' filament wires sand giant hum pot right next to the preamp might be worth checking out, as regards the hum. ..

Yes, it is cathode bypass on the power tubes and the supply is 117. When you are using the variac are you scaling the whole amp? In other words, you are supplying the amps primary voltage from the variac? If that is the case, then you are also scaling the heater supply. If you have that too low the ...

I pulled this out of a console(Model DPA-30-3 amp) and pictures are attached. Everything is new or NOS except the transformers and tubes which are original. I also did some modifications. I put in a fuse an on off switch, input switch for 2 sets of stereo inputs, indicator light which is wired to t...