5. Problem - Amp has a hum that doesn't change in level as you advance the volume control of your preamp
Areas to check - bad quad cap, bad ground inside the amp, bad tube filament that is leaking AC into the audio
6. Problem - Hiss, noise, crackling sounds on idle
Areas to check - Noisy driver tubes, noisy resistor on driver board (especially older carbon composition resistors), bad solder joint or bad solder trace on the driver board.
I have isolated the hum/noise to the amp by shorting the input leads from the preamp to the amp, my amp has a stepped attenuator so I'm able to use the amp without my DAC and preamp and have noted that hum is consistent and doesn't seem to vary however the hiss/crackling noise seems to come and go and is not consistent.
Both channels have the hum, crackle noise so i started by changing out the center driver tube with no improvement then I tried swapping side to side then different set's of driver tubes with no improvement.
I have pushed firmly on the PT while the amp is in operation and did not detect any notable difference in the hum I also tried tightening loosening the mounting screws with no positive results.
just for the heck of it i also changed from my KT-120s to Kt-88s and from GZ34 to 5AR4 to a WZ68 copper cap, no improvement or change.
I have noted that when I shut the amp down the hum stops but the crackling noise is still present for a few seconds (I'm guessing caps bleeding off?)
I have pulled the cover and visually inspected for an obvious bad solder joints using a magnifying glass at this point I have not re flowed any solder joints
Would the next logical step be to check quad cap and resistors on the driver board?
Keeping in mind that I'm a novice what would be the next trouble shooting steps should i take any tips or advise would be greatly appreciated