Nad C372 no sound, red light in power switch speakers a and b are green....

SOURCE: Amp wont switch off of stand-by

Both units have a problem with the output section. In case 1, the outputs are likely to be shorted. In case 2, the outputs are open. The low level and distortion come from you driving the speakers with the driver section of the amp. Both units will need to see a service provider.
Dan

SOURCE: nad c372 prob

The unit is detecting a problem and shutting down in what is usually called "protect" mode. Look for bad connections on the board near the voltage regulators.

Dan

SOURCE: nad c372 problem with left speaker output

Hiya, did you try to swop the inputs as well and see if the problem swops. Try that as the input could also be low. If so try change the cable.

If not there try cleaning out the balance pot with switch cleaner (have to open to that and only you are comfortable).

If thats not there then likely an internal problem and will have to send it in.
Best of luck

SOURCE: There is a distortion in

Hi,
If the distortion is also the same in the earphone jack of the unit, this is an indication that the fault was came from the unit itself. This kind of symptoms is technical and needs an experienced to isolate the fault from input circuitry, pre-amplifier stage, and in the sound output section of the unit.
The fault is caused by "Bad input cable cords", "faulty filter electrolytic capacitor" and/or bad solder joints in the said sections.
Replace/swap first the cables to ensure that the fault was not came from bad connections.
If the symptoms still persist after you've replaced the input cables, you must check bad solder joints (cracked, dried, cold solder) in the board. You should work in the brightest area or use table/portable lamp and magnifying glass because these are hard to spot. Check it also in the power supply board.
Let me know if the symptoms still persist after the above solution had been done to assist you further.
Regards,
Jdvillanueva