Slight hum in my amp. Is this normal?

Thanks, Ralph. To be clear, though, am I correct in believing that to the extent the asymmetry of the waveform corresponds to a 2nd harmonic component, neither a DC blocker nor a transformer would eliminate it?

Best regards,
-- Al

Atmasphere 5-24-2017
DC on the line occurs when 1/2 of the AC line (for example, positive going portion of the AC waveform) is loaded while the other half is not.

Space heaters or hair dryers on half power do just exactly that. So one half of the AC line can have lower amplitude due to the loading as a result.

But its still an AC waveform and so can travel through a transformer. But the output will still be asymmetrical. The asymmetry can be filtered out by a DC blocker which is a simple circuit consisting of 2 or 4 diodes that are bypassed by some large capacity electrolytic caps.

Ralph, I share Jim’s puzzlement about that. If a waveform that is asymmetrical above and below zero volts is sent into a transformer, I would expect that what would emerge from the output winding of the transformer is a waveform that looks similar (assuming that the frequency components other than DC are within the transformer’s bandwidth), but that has been offset up or down such that the zero Hz (DC) component is eliminated.

Best regards,
-- Al