Am I hearing things?

Is there any other issues I should know for a COMMON NEUTRAL*

Hi Elizabeth,

The first thing I would wonder is if the neutral wiring that is common to the two circuits is rated to be able to conduct 40 amps, which it would have to if and when 20 amps is being drawn from each of the circuits.

Also, I can envision that sort of arrangement being conducive to ground loop issues in some systems, because the unequal currents in the hot and neutral conductors, and their differing distances from the safety ground conductors, would tend to increase hum and noise voltages that are electromagnetically induced in the safety grounds. (I’m assuming that there are safety ground conductors, and that they are physically close to either the hot or neutral conductors)

Jim (Jea48) is more knowledgeable about this kind of thing than I am, though, especially from a code standpoint. We’ll see what he has to say.

Best regards,
-- Al

To add some perspective to Jim’s (Jea48’s) good comments about voltage drop, if the wiring that was replaced is say 50 feet long and during dynamic peaks the current drawn by the system (and anything else that is connected to the corresponding outlets) is say 8 amps (corresponding to about 1000 watts; the aforementioned Bryston amp alone can draw considerably more than that at max power), the change from 12 gauge to 10 gauge will increase the voltage provided to the amp and any other components that are not powered by the regenerator by about 0.5 volts.

That doesn’t seem like a lot, but I suppose it might make some difference sonically. On the other hand, though, if the line voltage at the OP’s location is already particularly high, and perhaps above what is sonically optimal for the particular amp (for example, in terms of the resulting internal temperatures), I wonder if the increase might be in the wrong direction.

In any event, in addition to Jim’s suggestion about obtaining a polarity checker, it may be informative if the OP were to obtain a multimeter and measure the line voltage at various times of the day and evening.

Regards,
-- Al