Follow up questions regarding my NAD C375BEE


I recently placed a posting regarding the protection circuit activating on my NAD C375BEE running Totem Model One Signature speakers. A poster on another forum indicated that the NAD is not robust enough to operate at the impedance load presented by the Totems and that I have damaged the amplifier. Prior to my purchase I did some internet research and found many folks running Totem speakers (including the Mani 2!) using NAD amplification without this issue. Any information or guidance regarding this dilemma would be greatly appreciated. If any readers noticed my first posting I failed to include my REL Strata II subwoofer in my roster of equipment. The REL developed a hum when I introduced the NAD into my system. Coincidence or related to my problem?
Thank you, Joseph
joseph54
The hum you have picked up in your sub is probably a ground loop from the offset differential of the ground planes between the amp and the sub. These can be difficult to resolve. Might try lifting the ground on the amp and see if it goes away (or sub.)
Sometimes, the ground differential can be enough to cause such a reaction by the amp. However, my gut tells me your amp has a problem. I would pack it off to a service center for a check. NAD equipment is decent but historically, it has been known to have some issues. This series is no exception.
The NAD is certainly robust enough to drive the Totem's. Even though the speaker has a relatively low impedance in a narrow range (3.8 ohms) it is not that hard of a drive due to the speakers phase angle performance. Any decent amp should work well with these speakers.
Thank you Bigtee....I am not ignorant but certainly technologically challenged. How does one lift a ground? I will embarrass myself by inroducing a question whose answer is no doubt known to many, if not most! Thank you...Joseph
Easiest way is to use a cheater plug ... 3 prongs to 2 prongs plug.

Rich
Rar1, thank you. Believe it or not, that is what I thought but I wouldn't attempt that without the assurance from someone like yourself. Thank you!
Are you running the REL through the low level or the high level inputs?
Wow, I was going to say the suggestion that the NAD can't handle the Totems is ridiculous. Something else is going on there.
I'm not positive the NAD uses a 3 lug connector (some NAD amps don't) but if it does, use the cheater as Rar1 suggests and see if the hum goes away.
If the NAD does not use a 3 prong connector, use the cheater at the sub power cord.
Another trick is to use a small gauge wire connected from the chassis of the NAD to the sub amp chassis. It may have a ground lug on the sub-not sure as I'm not familiar with this brand. Worth a try.
As for your amp going out on protection, is it both channels or one channel? If both, I would suspect something in the power supply of the amp. This would require a visit to the shop for correction.

Could the protection circuit activating be caused by excessive heat? A basic question, but I must ask if there is plenty of room around the NAD, top and both sides? Is it in a cabinet?
"I recently placed a posting regarding the protection circuit activating on my NAD C375BEE running Totem Model One Signature speakers."

"The REL developed a hum when I introduced the NAD into my system. Coincidence or related to my problem? "

Is the protection circuit activating on the NAD, as well as having the hum from the sub?
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.
Update:
It looks like the OP started a thread at Audioholics at the same time, it's about the NAD C375, Totem Ones as well with the NAD protection circuit activating too. Later on in that thread, he adds that his previous integrated, an Anthem 225, had issues too. One speaker was much quieter so he had to adjust the balance knob and decided the Anthem was going and bought the NAD.

Now the NAD needs the balance adjusted too, but it's shutting down as well. Anyway, it's all there in the thread, 2 capable guys are helping him and they think the Totem ones or the sub is damaged.
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
One more thought: Make sure that the black wire from the REL is connected to one of the negative (probably black) speaker terminals on the amp, and not to one of the positive (probably red) speaker terminals. If the black wire is interchanged with either the red or the yellow wire from the REL, and is connected to a positive speaker terminal on the amp, I believe that could account for all of the symptoms you have described here and in the other thread that was referenced above, and (consistent with what you have reported) could result in the amp shutting down even if the sub is turned off.

Regards,
-- Al
"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)."

That could be the problem. If you play a recording that normally has a solid center vocal image, wiring the speakers out of phase with each other will make the vocals sound like they are coming from one of the side walls, and not the center. Its very easy to hear. You can't miss it.

Another cause for the channel imbalance could be your room. If you have something like the right speaker near a corner and the left near a free space, one speaker will have to work harder to match the volume of the other one.

Also, if you bought your speakers used, go over all the screws and make sure they are tight. They can loosen up over time.
ZD, thanks for the good elaboration on the point I raised.

Joseph54, regarding my other point, even if you have verified that the black wire from the REL is connected to a negative output terminal on the amp, I would not rule out the possibility that the cable itself is miswired. In other words the black wire could conceivably be connected to a pin on the Neutrik connector which should be connected to either the yellow or the red wire, and vice versa.

Again, the possibility that the sub's ground (which should be the black wire in the cable) is connected to a positive output terminal of the amp seems very consistent with the symptoms you have reported in all of your threads, here and elsewhere.

Regards,
-- Al