by Soundguy2856 » Sat Jun 29, 2013 7:24 pm
I've just finished the first of 2 Mark III restores using SDS cap board and Poseidon driver board. First test was fine using a fair set of tubes I had on hand. Power is good....freq response is good....distortion is good ...basically all is as expected but I have about 30mV of residual hum in the noise floor. Is that to be expected? The freq of the residual is 60Hz which makes me think it's source is the half wave bias supply.....but maybe, with this combination, 30mV is normal? Thanks for your input.