I would be VERY curious to see the DC line voltage monitored with a differential scope that records the AC leakage of any sort (anything that is not DC) and see what it tells you all.
DC is DC, and what you think is coming in is 100% immaterial till you show it out the DC side of the supply. An HP differntial voltage meter is thousands of times more sensitive than the human ear. If your DC signal has noise in it, what is it and what magnitude? I really can't see where a 0 dB offset average over time is going to be "heard". This test measures anything that isn't pure DC to the set reference value (sag, spikes, ripple...you name it) and records it.
Most wall to electronics issues are crappy plugs that change contact resistance with heat due to poor contact pressure. All those expensive cords fix that, but what's in the middle is what people think they get! No, it's usually the plugs. An IEC plug is not even an 100% usable interface distance. The plug makes make spec "contact" till about two-third of the way in. A good hospital grade plug has spec contact pressure almost immediately. Go play around with them and see. My IEC plugs work loose on my equipment all the time. The hospital grade wall plug? Never.
Romex right from the wall to the transformer with twist lock caps? Way better than a poor retention IEC plug (I HATE those plugs!). A hospital grade wall outlet and plug on the back of your amp would be about three times the retention force of an IEC plug / socket. The continuity is all about the contact pressure with temporary sockets.
DC is DC, and what you think is coming in is 100% immaterial till you show it out the DC side of the supply. An HP differntial voltage meter is thousands of times more sensitive than the human ear. If your DC signal has noise in it, what is it and what magnitude? I really can't see where a 0 dB offset average over time is going to be "heard". This test measures anything that isn't pure DC to the set reference value (sag, spikes, ripple...you name it) and records it.
Most wall to electronics issues are crappy plugs that change contact resistance with heat due to poor contact pressure. All those expensive cords fix that, but what's in the middle is what people think they get! No, it's usually the plugs. An IEC plug is not even an 100% usable interface distance. The plug makes make spec "contact" till about two-third of the way in. A good hospital grade plug has spec contact pressure almost immediately. Go play around with them and see. My IEC plugs work loose on my equipment all the time. The hospital grade wall plug? Never.
Romex right from the wall to the transformer with twist lock caps? Way better than a poor retention IEC plug (I HATE those plugs!). A hospital grade wall outlet and plug on the back of your amp would be about three times the retention force of an IEC plug / socket. The continuity is all about the contact pressure with temporary sockets.