Follow up questions regarding my NAD C375BEE

It would seem to me that you have two issues here; perhaps they are related, but it is also quite possible that they are not related. The first thing I would do is isolate the two conditions (protection circuit and hum) by completely removing the sub from the system. Secondly, I wouldn't consider it a forgone conclusion that the amp is damaged just because the protection circuit is activated, especially if you powered off shortly afterwards.

I have the 375 also, and I think it to be a fine amp capable of driving just about any speaker. I find it puzzling that some would suggest it isn't robust enough. That just doesn't seem to be a rational suggestion; clearly information is missing somewhere.

When the sub is completely disconnected from the amp (all wires and interconnects removed), is the protection circuit still activating? If so, the next item to examine is the connections to the speakers. The 375 has two sets of speaker posts (A and B). Are you using only one set (A or B) of speaker posts or are you using both speaker posts (A and B)? If using both, what speakers are the second set of posts connected to?

On the back of the amp, I prefer the soft clipping be turned off but this is just a matter of preference. Also, the amp should be set to stereo. One more idea: there is a fuse with access from the back of the amp. You may want to pull the fuse out and take a peek at it. Perhaps the fuse is blown. Keep in mind a blown fuse is a symptom, not the cause. You will still need to trouble shoot to determine what caused the fuse to blow.

If the protection circuit is not activated when the sub is completely disconnected, then there is a problem with the way the sub is hooked up and connected to the amp.

We can give more specific help once we have a better idea how the amp performs independently and without any sub connected.

Pgawan2b, I do think you are offering good advice, however, the part about looking at the fuse makes no sense. That is an AC power fuse, so if it is blown, the unit will be totally dead and not work. The unit works, but with the protection circuit activating prematurely.

Tls49, good point and thanks for the correction.

A number of good comments and suggestions have been provided above. I'll add one further thought while awaiting feedback on what has been suggested:

Are you certain that the two speakers are connected with the same phase, i.e., that + and - are not interchanged in the connections to ONE speaker?

If the two speakers are not connected in phase with each other, some of the results would be vague and diffuse imaging, and weak bass. I'm thinking that in some circumstances a result might also be the channel imbalance you have perceived, and also a perceived reduction in volume (which would be further compounded in one channel by the balance control offset). If so, to achieve reasonable volume and bass perhaps you are turning the volume control up high enough to overload the amp, with the clipping distortion that would normally result from doing that perhaps being prevented by the amp's soft clipping feature and/or by the amp's unusually large dynamic headroom.

Also, as Pgawan2b suggested, verify that the bridged mode switch on the rear panel is set to off/stereo. If the speakers are connected as a normal stereo pair but that switch is set to bridged mode, it would cause similar effects to those I described above for an out of phase speaker connection.

Regards,
-- Al