NAD C375BEE protection circuit activating.

[unacat]

Than you, I had no idea that something that seemed so benign could be the root of the problem. At least this is a positive step in troubleshooting that I can take.

 

[unacat]

Whoa...as I noted in my reply to PENG I had no idea that something that appeared to me to be a non issue may be the cause of my troubles. Does the ohm meter measure the DC resistance at the speaker terminals when they are not receiving power from an amplifier? If this is the issue is there a chance that the protection circuitry was simply performing it's designated function and that the amplifier is not for certain damaged? What type of expert help would that be, sending my speaker(s) to Totem? Apologies for flooding you with questions, but although I am not an ignorant person, I am technologically challenged. I again appreciate your guidance, what a wonderful group of fellow enthusiasts on AUDIOHOLICS!

 

[TLS Guy]

Whoa...as I noted in my reply to PENG I had no idea that something that appeared to me to be a non issue may be the cause of my troubles. Does the ohm meter measure the DC resistance at the speaker terminals when they are not receiving power from an amplifier? If this is the issue is there a chance that the protection circuitry was simply performing it's designated function and that the amplifier is not for certain damaged? What type of expert help would that be, sending my speaker(s) to Totem? Apologies for flooding you with questions, but although I am not an ignorant person, I am technologically challenged. I again appreciate your guidance, what a wonderful group of fellow enthusiasts on AUDIOHOLICS!

The speaker must be disconnected from the amp to do the test.

It is simple, you set the meter to where it will accurately measure a resistance less then four ohms.

Then connect the prongs across each set of terminals in turn and record the readings.

And yes, in the light of this information your amp protection may be working as intended.
However the possibility of damage can not be discounted.

We had no idea that there was anything to suggest a speaker problem.

One other thing. Are all your speaker cables visible, and not behind walls where a rodent could have damaged them?

I ask this, as an amp sending DC offset is usually destroyed at the same time it damages the speaker.

I have had one further thought about this unusual situation of yours. Your sub is humming and therefore suspect. I can think of a way that your sub might have caused the damage. Most amps output stages will amplify DC. The amps don't, as there is usually a DC blocking capacitor at the input stage.

However a designer would not probably think of DC being applied to the speaker terminals. If your sub did produce even a small DC offset at the speaker level input terminals, it would get back to the high gain circuit of the amp through the amps negative feedback circuit. This would then be amplified and appear as DC off set at the output. I suppose it is theoretically possible that there could be enough DC offset to damage a loudspeaker voice coil over time without destroying the power transistors.

I would suggest you see if there is a DC voltage across the speaker terminal inputs of your sub. There should be absolutely zero volts at the terminals. Put your meter on the lowest voltage setting. Your meter might not be able to measure this even if there is a problem. This might take a high impedance amplified meter or scope to detect it.

If in fact this is what has caused the problem, it will be one for the books.

One thing I'm certain of, is that if one of your speakers has a low DC resistance, something has caused DC offset.

 

[sharkman]

The reason that I purchased a new amplifier was that I found that I had to turn the balance on my Anthem way to the right speaker to balance the sound. Since the Anthem was fifteen years old I assumed that it may need repairs so I purchased the new amp. Since introducing the NAD I found that I still must adjust the balance way to the right channel. If that speaker is in fact defective, does that have the potential to be a problem that might trigger the amp to shut down? Thx...Joseph

This symptom is at the heart of your situation, since you have to adjust the NAD's balance as well. Are there any more symptoms that you are experiencing?

Just in case it hasn't been mentioned yet, when trouble shooting make sure the NAD is off when disconnecting/connecting speakers or anything else. I'm hoping the NAD isn't damaged and I concur with the idea that it's the speaker. NAD's earlier models have been spotty for reliability(C270, C272) but they were rebuilding their brand after the purchase of the company around the year 2000. The current line up has been better, or so I've read. I've got a C326BEE, and it's been flawless.

 

[unacat]

No, sharkman. Unfortunately after trying to describe my situation in detail I failed to describe what is the most important piece of the puzzle little realizing the significance of the speaker balance problem. It was my understanding that NAD was putting an emphasis on improving the quality and dependability of their products that prompted me to purchase the C375BEE which would more than likely be viewed by many as step down from the Anthem. And thank you but, yes, i always power down before making any connections. Joseph

 

[TLS Guy]

This symptom is at the heart of your situation, since you have to adjust the NAD's balance as well. Are there any more symptoms that you are experiencing?

Just in case it hasn't been mentioned yet, when trouble shooting make sure the NAD is off when disconnecting/connecting speakers or anything else. I'm hoping the NAD isn't damaged and I concur with the idea that it's the speaker. NAD's earlier models have been spotty for reliability(C270, C272) but they were rebuilding their brand after the purchase of the company around the year 2000. The current line up has been better, or so I've read. I've got a C326BEE, and it's been flawless.

I agree with that. The speaker is now the likely cause of the reset now. However if that driver has low DC resistance, then the speaker is not the primary cause, but now the cause triggering the reset.

So the OP needs to get DC resistance measurements of his speakers. He needs to check for any connection between the +ve and -ve of his speaker leads with his ohm meter.

He needs to disconnect the sub from the NAD, power it up and check for any DC voltage at the speaker level inputs.

I will be off line for the next few hours. We came to Eagan for a grandchild's birthday and are heading back to Benedict. Anyhow, now is the time to collect data.

Since the Anthem still works, I have a feeling, unlikely as it may seem at first glance, that the sub is in fact the prime originator of this saga.

 

[unacat]

Yes, all of my cables are visible and have relatively easy access. I see a meter available on AMAZON described as 'LCD Digital Ohm Voltmeter AC DC Voltmeter Multimeter' for $7.59, is this the correct meter to measure the Totems and the REL sub? The REL has a Neutrik connector, can I measure at the speaker leads and what do measure one positive and the ground? The situation that you describe with the REL is a bit over my technical knowledge but I believe that I understand. In order to set the Ohm meter so that it will read less than 4 ohms, do I set it at 4 ohms or lower?
Questions, questions, questions.....I had no idea when posting this issue that I would find someone so willing to share their knowledge and time. My humble and sincere thanks. Joseph

 

[TLS Guy]

Yes, all of my cables are visible and have relatively easy access. I see a meter available on AMAZON described as 'LCD Digital Ohm Voltmeter AC DC Voltmeter Multimeter' for $7.59, is this the correct meter to measure the Totems and the REL sub? The REL has a Neutrik connector, can I measure at the speaker leads and what do measure one positive and the ground? The situation that you describe with the REL is a bit over my technical knowledge but I believe that I understand. In order to set the Ohm meter so that it will read less than 4 ohms, do I set it at 4 ohms or lower?
Questions, questions, questions.....I had no idea when posting this issue that I would find someone so willing to share their knowledge and time. My humble and sincere thanks. Joseph

Yes, that meter is OK to measure the speakers. Put it on the lowest ohm range. It may well not be adequate to measure DC at the sub terminals. This may well require a high impedance amplified meter. These are too spendy for the occasional user. A scope would also identify the problem. You should consider, having the sub checked out by someone with appropriate knowledge and test gear, if your measurements point to that as a possibility.

 

[unacat]

It is an older REL, I believe I will just disconnect it and put it in the closet, they are very musical pieces though. Thank you for your guidance on using the meter, I will order it and with my AMAZON PRIME will get two day shipping. If you do not mind I will share the results with you and perhaps you might guide me from there. Thank you so very much, Joseph.

 

[PENG]

Yes, all of my cables are visible and have relatively easy access. I see a meter available on AMAZON described as 'LCD Digital Ohm Voltmeter AC DC Voltmeter Multimeter' for $7.59, is this the correct meter to measure the Totems and the REL sub?

If you are talking about this meter LCD Digital Ohm VOLT Meter AC DC Voltmeter Multimeter: Amazon.com: Industrial & Scientific it looks like the lowest ohm range is 200 ohm so set it to 200 ohm. It is right at the bottom of the dial. As to measuring the Rel's input for d.c. voltage you can try starting with the 20V range, then 2V and then 2mV if the value is too low for the display. It is such a cheap meter so I am not sure if it will be accurate enough for the job. I wouldn't use that thing for anything higher than 50V as I am not sure if it has any safety certification.

The REL has a Neutrik connector, can I measure at the speaker leads and what do measure one positive and the ground? The situation that you describe with the REL is a bit over my technical knowledge but I believe that I understand. In order to set the Ohm meter so that it will read less than 4 ohms, do I set it at 4 ohms or lower?

I thought he suggested you measure the Rel's speaker inputs to see if there is any d.c. voltage. He said "He needs to disconnect the sub from the NAD, power it up and check for any DC voltage at the speaker level inputs."

So DO NOT use the ohm range of the meter for this part, set it to the DC voltage range as I mentioned above. He said set it to the lowest range, for this $7.59 meter that seems to be 200 mV base on the blurry picture on the Amazon website, but you should read the manual just to be sure.

As I mentioned above, I would set it to the 20V range first, if the reading is too low, or erratic, then set it to 2V and if the reading is still too low then try the 200 mV and that's the minimum whether it works or not. You should just connect the probes to the speaker input terminals with nothing connected to the sub other than the 120V power supply. The positive (normally red) probe to the +ve speaker terminal, and the other probe (normally black) to the -ve speaker terminal.

Have you try disconnecting all speakers and see if the amp still shutdown, and then connect one at a time? Actually, a saver way to do it is as follow:

1) Disconnect both speakers.
2) Reconnect the one that sounds normally loud to the same amp channel that it was previously connected to.
3) Gradually turn the volum up from zero to say, up by 20 degree, listen to the music for a while and if it sounds normal after 10 minutes, increase volume to say the 9' O Clock position (90 degrees). If the amp still holds after another 10 minutes then you know this speaker and the amp channel powering it are not the problem.
4) Move this same speaker to the other side and connect it to the amp channel that previous powered the quieter speaker. Repeat the same test procedure. If the amp shuts down, then the problem is not the speaker, but the amp has one bad channel. If the amp still holds, then you can be 90% certain the quieter speaker may be the culprit. The other 10% would be the REL subwoofer, but to verify that you would have to be willing to hook those up one at a time. I really wouldn't worry about causing further damage if you keep the volume low, but it is your speaker so if you are concern then you shouldn't do it.

 

[unacat]

Thank you, PENG. I did not realize that purchasing a low priced meter would compromise my measurements, i bought this one as following this issue I may never use it again due to my limited knowledge regarding these matters. Because the REL uses a neutrik connection can I check the voltage at the speaker leads? There are three. two leads connect to the positive speaker terminals and one to a negative speaker terminal. Thank you for the advice on a safe troubleshooting method with the possibility of a bad speaker, it provides me with another method to track down the problem. I appreciate your continued support in my challenge to get back to the music. I will let you know how I make out. Joseph

 

[PENG]

Thank you, PENG. I did not realize that purchasing a low priced meter would compromise my measurements, i bought this one as following this issue I may never use it again due to my limited knowledge regarding these matters. Because the REL uses a neutrik connection can I check the voltage at the speaker leads? There are three. two leads connect to the positive speaker terminals and one to a negative speaker terminal. Thank you for the advice on a safe troubleshooting method with the possibility of a bad speaker, it provides me with another method to track down the problem. I appreciate your continued support in my challenge to get back to the music. I will let you know how I make out. Joseph

I am not sure what you mean as Neutrik makes all sorts of connectors. May be a photo would help. To keep it simple, just disconnect the speaker leads at the amplifier end (not at the sub) and measure the voltage at that end, in this case you should only have two wires to worry about, one red and one black and I don't have to guess.

Have you tried disconnect everything and starting connecting just the Totem that sounds normally loud first? I would definitely leave the sub out of the equation for the time being. It must be a really old model as I could not find any data sheet or manual for it on the web. When you had the Anthem, did you hook up that same sub the same way?

 

[unacat]

Sorry for the delay in my response, PENG. I was working today and as it turns out 'message boards' are blocked on the corporate system which prevented me from reading your last posting. I am an AMAZON Prime member so the ohm meter will arrive on Wednesday so I think that I will wait until that arrives and will check my Totem and the REL before I do any more troubleshooting. Before I posted on AUDIOHOLICS and received such knowledgeable and patient response from members such as yourself I emailed NAD service support and they did allow that repeated engagement of the protection circuit can cause damage to the amplifier. I will check the readings from the speaker(s) and, if you do not mind, share them with you so that you can make an evaluation based on those readings. Thank you for your continued interest and willingness to share your time and knowledge with me, I feel that I would have not only been stymied by my efforts to troubleshoot but more than likely caused major damage to my amplifier. Joseph

 

[PENG]

Sorry for the delay in my response, PENG. I was working today and as it turns out 'message boards' are blocked on the corporate system which prevented me from reading your last posting. I am an AMAZON Prime member so the ohm meter will arrive on Wednesday so I think that I will wait until that arrives and will check my Totem and the REL before I do any more troubleshooting. Before I posted on AUDIOHOLICS and received such knowledgeable and patient response from members such as yourself I emailed NAD service support and they did allow that repeated engagement of the protection circuit can cause damage to the amplifier. I will check the readings from the speaker(s) and, if you do not mind, share them with you so that you can make an evaluation based on those readings. Thank you for your continued interest and willingness to share your time and knowledge with me, I feel that I would have not only been stymied by my efforts to troubleshoot but more than likely caused major damage to my amplifier. Joseph

No problem at all, I certainly would not encourage anyone to browse message boards at work. If I were the NAD support I would have given you that same kind of typical response. Just that at one point, you have to decide on sending the amp to NAD for checkup/repair, or attempt to troubleshoot to try determining whether the amp or the speaker(s) is(are) the problem. Measuring the dc. resistance of the speakers does not always tell the whole story either but it will tell you if both speakers measure the same or one of them is shorted, or read really low. While waiting for the meter, you probably should contact Totem for their troubleshooting suggestions and at the very least ask them what readings (d.c. resistance) to expect if the speaker is not damaged.

Do you have another speakers that you know for sure are not damaged?

 

[TLS Guy]

No problem at all, I certainly would not encourage anyone to browse message boards at work. If I were the NAD support I would have given you that same kind of typical response. Just that at one point, you have to decide on sending the amp to NAD for checkup/repair, or attempt to troubleshoot to try determining whether the amp or the speaker(s) is(are) the problem. Measuring the dc. resistance of the speakers does not always tell the whole story either but it will tell you if both speakers measure the same or one of them is shorted, or read really low. While waiting for the meter, you probably should contact Totem for their troubleshooting suggestions and at the very least ask them what readings (d.c. resistance) to expect if the speaker is not damaged.

Do you have another speakers that you know for sure are not damaged?

The DC resistance of the woofers is 3 ohms. The resistance from the inductors will be insignificant.

If one reads less then 3 ohms it has shorted coil turns.

One of the nice things about this series of drivers, is that they have good response to 3 KHz without nasty breakup modes, and then roll of acoustically second order from 3 KHz. So it makes for simple crossover design.

 

[PENG]

The DC resistance of the woofers is 3 ohms. The resistance from the inductors will be insignificant.

If one reads less then 3 ohms it has shorted coil turns.

One of the nice things about this series of drivers, is that they have good response to 3 KHz without nasty breakup modes, and then roll of acoustically second order from 3 KHz. So it makes for simple crossover design.

I was concerned he would be measuring through the crossover and the parallel effect of the woofer/tweeter in parallel. I just checked the Totem's manual and was happy to see that the model 1 signature can be bi-amped so he can just remove the jumper to measure the woofer separately. The effect of the crossover would be negligible for the d.c. so yes he should see 3 ohms or very close to that and both speakers should measure the same.

 

[TLS Guy]

I was concerned he would be measuring through the crossover and the parallel effect of the woofer/tweeter in parallel. I just checked the Totem's manual and was happy to see that the model 1 signature can be bi-amped so he can just remove the jumper to measure the woofer separately. The effect of the crossover would be negligible for the d.c. so yes he should see 3 ohms or very close to that and both speakers should measure the same.

He won't have to remove the jumpers, as there is always at least one capacitor in series with the tweeter, which will block DC and cause infinite DC resistance on the high pass circuit.

 

[PENG]

He won't have to remove the jumpers, as there is always at least one capacitor in series with the tweeter, which will block DC and cause infinite DC resistance on the high pass circuit.

True enough, but it is easy to remove a jumper, for an inexperienced person capacitor's behaviour can be confusing too.

 

[unacat]

The Totem Signatures have two sets of binding posts and I have them biwired so the jumpers have been removed, I can therefore test the mid / woofer only. Why would the mid / woofer only be affected by a bad signal, the crossover? Thanks.....Joseph

 

[PENG]

The Totem Signatures have two sets of binding posts and I have them biwired so the jumpers have been removed, I can therefore test the mid / woofer only. Why would the mid / woofer only be affected by a bad signal, the crossover? Thanks.....Joseph

The tweeter can be damaged too and it does not have to be a bad signal, it can simply be too strong a signal such as a 200W amp driving you Totem with volume at maximum. That's of course just an example.

As TLSG said the tweeter will have little or no effect even if you leave the jumper there due to capacitor blocking a d.c. signal from the meter, as long as you wait for a split second when the little capacitor gets charged up and the meter reading becomes steady.

It may be just me, I would still bet money on the amp being problem, most likely the protective circuit itself being defective and got too sensitive. I base my guess on the fact that you said it would work for 5 minutes. If you have a blown transistor, the amp would have shutdown right away or blow a fuse if it is protected by fuses. If it is the amp, then I would bet only one channel has a problem, could be a partially shorted transformer in one of its two secondary winding.

The REL sub could be next in line as a suspect but I still would like to know if the sub was connected the same way to your previous Anthem amp. If it was, then I would still bet heavily on the amp being the problem.