I have the Sherbourn PA 7-350 power amp that I bought from Emotiva when they had the clearance sale. This is a really solid and well built amp but it randomly shuts down due to its protection circuit kicking in. Sometimes I can watch a whole movie without a problem and sometimes it shuts down in about an hour. Here are things to note:-
1. The shutting down is not related to volume, it can shut down even when nothing is playing.
2. The shutdown is not due to overheating problems as the amp is in a well ventilated place.
3. Shutdown is accompanied by mainly the channel 7 lights blinking which id the front right speaker with occasional channel 6 light blinking which is the side right speaker.
Remedies that I have tried:-
1. replaced my XLR cables between pre/pro and amp but it made no difference.
2. Replaced the speaker cable for both those channels but no difference.
3. Swapped speakers to rule out any speaker problems but nothing changed.
4. Swapped the XLR cables to ascertain if it's my pre/pro but no change which means my pre/pro is intact.
Things that I will be trying:-
1. To disconnect all speakers and check wiring to rule out lose connections on all channels.
2. Bypass the 20Amp mains power stabiliser/conditioner that feeds the amp.
If anyone has any experience with such matters then help will be appreciated as I'm still in the process of trouble-shooting.
I'm wondering if there are other members of this forum who are using the same power-amp.
I'm hoping that it is not an over-sensitive protection circuit - any electronic enthusiasts or engineers here that would know how to resolve this?
1. The shutting down is not related to volume, it can shut down even when nothing is playing.
2. The shutdown is not due to overheating problems as the amp is in a well ventilated place.
3. Shutdown is accompanied by mainly the channel 7 lights blinking which id the front right speaker with occasional channel 6 light blinking which is the side right speaker.
Remedies that I have tried:-
1. replaced my XLR cables between pre/pro and amp but it made no difference.
2. Replaced the speaker cable for both those channels but no difference.
3. Swapped speakers to rule out any speaker problems but nothing changed.
4. Swapped the XLR cables to ascertain if it's my pre/pro but no change which means my pre/pro is intact.
Things that I will be trying:-
1. To disconnect all speakers and check wiring to rule out lose connections on all channels.
2. Bypass the 20Amp mains power stabiliser/conditioner that feeds the amp.
If anyone has any experience with such matters then help will be appreciated as I'm still in the process of trouble-shooting.
I'm wondering if there are other members of this forum who are using the same power-amp.
I'm hoping that it is not an over-sensitive protection circuit - any electronic enthusiasts or engineers here that would know how to resolve this?
did you check dc on the output?
shutting may be dc sensing circuit triggering
kind of on the edge
shutting may be dc sensing circuit triggering
kind of on the edge
do your front left and right speakers present an unusual load to the amp?
what is the overall impedance and crossover like?
what is the overall impedance and crossover like?
Thanks Adason, that is something that I have not checked simply because I don't have a multi-meter but I'll buy one for this purpose. I was given similar advice on a different forum, here it is:-
If you have a volt meter set it to 2 or 20v DC range and connect it to your speaker terminals. There should be less than .1 volts across the wires.DC offset is a leading cause of protection activation. Ideally there should be 0 to .01 VDC. Check it with volume all the way down.
Feel free to add to the above advice.
I guess I need to do that with all speakers, is that right?
All my speakers are rated at 4 ohms and the amp is capable of driving them. Even when I swapped the front left and front right speakers using separate new speaker cables, the amp still still goes into protection mode randomly with the channel 7 (right speaker) light blinking. This shows that there is nothing wrong with the front right speaker and associated speaker cable.
well you could try disconnecting them to see if it behaves differently.
with no test equipment how can you be certain that the speaker impedance isn't dipping too low at some point in the response?
seems like a lot of people are trying to sell these, googling for info on that amp there's a multitude of them for sale, perhaps they have a common fault with the protection circuit.
with no test equipment how can you be certain that the speaker impedance isn't dipping too low at some point in the response?
seems like a lot of people are trying to sell these, googling for info on that amp there's a multitude of them for sale, perhaps they have a common fault with the protection circuit.
You are right, I do need a good multimeter to measure the impedance of each speaker. You may be right about a common manufacturing fault as I bought 2 units and they are both displaying the same problem 😱
I'm really hoping that it is something minor that is causing the problem
Any suggestions on a good multimeter that has impedance measuring abilities too? I've noticed most multimeter have a resistance measuring mode.
Thanks Adason, very interesting video but I really don't want to go through that process. What I did to rule out a faulty speaker and the possibility of impedance dropping to low is that I swapped my front left and front right speakers using new and speaker cables and the error light still shows up on channel 7 (front right speaker). Hence, the speaker is not faulty.
I'm thinking of removing my power conditioner from the chain to see if it makes a difference.
The amp goes down even when nothing is playing through it, it is not volume or frequency related.
Hi Turk, actually I have not done that. However, today I managed to remove the power conditioner from the chain and will be testing the amp to see if that makes a difference. Really hoping it does.
I would buy a multimeter and check the DC output. Meter does not have to be anything special, literally the cheapest meter available that can measure DC voltage with 0.1V or better resolution will be adequate for diagnosing a DC offset problem. Measure the DC voltage when you first turn the amp on, and again after it has been running for a while.
If the DC on every channel measures OK (near 0V), I would try disconnecting all speakers and running the amp for an extended period to see if it goes into protection. If that corrects the problem then you know the speakers are the issue.
If that doesn't help then try running the amp with no inputs connected. If that corrects the problem then you know the problem is with your sources or input cables.
It could also be that your mains line voltage goes either too low (brownout) or too high (surge) and causes a protection circuit in the powersupply to trip. If this is the problem it will be difficult to diagnose without fairly capable test equipment. Don't attempt to measure the line voltage with a cheap multimeter.
If the DC on every channel measures OK (near 0V), I would try disconnecting all speakers and running the amp for an extended period to see if it goes into protection. If that corrects the problem then you know the speakers are the issue.
If that doesn't help then try running the amp with no inputs connected. If that corrects the problem then you know the problem is with your sources or input cables.
It could also be that your mains line voltage goes either too low (brownout) or too high (surge) and causes a protection circuit in the powersupply to trip. If this is the problem it will be difficult to diagnose without fairly capable test equipment. Don't attempt to measure the line voltage with a cheap multimeter.
I'd like to thank all fellow members in this thread for being so kind and willing to help me troubleshoot my problem.
After checking all my speakers, speaker cables, XLR cables, processor - I finally decided to remove the power conditioner from the chain and plugged the amp straight into mains power and that has resolved the problem. Not only that, I've noticed that the sound has improved as it has a greater sense of refinement when listening to content that I know well. It is as if the amp could not draw the power it needed to perform normally. Furthermore, there was something in the output of the power conditioner that was triggering the protection circuits in the amp.
Just as an added protection, I decided to introduce a Volt-Guard in the chain that protects the amp from over or under voltage. The Volt-Guard does not tamper with the mains power at all, it only shuts down the device during over-voltage, under-voltage and dangerous power-surges.
After checking all my speakers, speaker cables, XLR cables, processor - I finally decided to remove the power conditioner from the chain and plugged the amp straight into mains power and that has resolved the problem. Not only that, I've noticed that the sound has improved as it has a greater sense of refinement when listening to content that I know well. It is as if the amp could not draw the power it needed to perform normally. Furthermore, there was something in the output of the power conditioner that was triggering the protection circuits in the amp.
Just as an added protection, I decided to introduce a Volt-Guard in the chain that protects the amp from over or under voltage. The Volt-Guard does not tamper with the mains power at all, it only shuts down the device during over-voltage, under-voltage and dangerous power-surges.
It is a British company and I don't want to mention their name because they do make excellent products and their service is excellent. I've never had a problem with their power conditioners but it seems that in this case the amp did not like the power it was receiving from this conditioner. It was a relay based stabiliser that stabilises power by physically activating relay switches (taps) within milliseconds. Hence it does not give out a constant power stream like a solid state voltage regulator. That and the possibility that the amp was not able to draw the power it needed may be the problem. The 30Amp Volt-Guard that I have now incorporated is by the same company.
oh well....glad your problems resolved...sincerely hope that no one else in the market place is affected by this...