Hi!
I've got this problem with my center. I can't seem to fine the reason. I've got a sony prosessor, two NAD 216 and a 214 bridged for the center. Got some Mirage FRX9 to go with them, pluss a Center in the same brand. Think its called C2 or something.. I've got this noise in the center, much like the wind blowing outside. This won't stop even on mute. I haven't sent it in on a check, but - could it be the amp that makes this noise? The strange thing is that sometimes the noise is gone.. Go figure.. I would guess it's the amp ...

Kjetil .

KJ, if mute doesn't stop the noise, it has to be from that point on. Check each connection, and try cable substitutions. If the bridging is switch-selected, try (with the amp OFF!) flipping the switch back and forth a few times to clean the switch contacts.

Another thing to try is see if the noise happens with the amps' inputs disconnected, and with the input shorted. Also, one step at a time, swap a working channel or component or cable to the channel with the problem, to eliminate one thing at a time.

The last thing to check is the speaker itself, which includes the internal crossover components. To do this, temporarily swap speakers and see if the same speaker or another one makes the noise.

The idea is to narrow down the problem by seeing when you can make the noise move to another channel or speaker, thus pinpointing the noise source.

Larry
www.fineelectricco.com

Thanks Larry,

I'll give it a shot, and see what happens.

Kjetil

It sounds like amp noise. Have seen some amps do it on their own (lesser quality amps), and have seen poor quality interconnects to the amps induce noise that becomes amplified. Your amps are probably music sensing which is why you don't notice the noise from time to time, until the noise gets picked up and the amp turns on to amplify it. Good luck. Why are you bridging you center channel? Be careful when you bridge, I had a manufacturer recommend bridging the center in their system until they realized 125watts bridged to 250 into 4ohms was too much for their speakers (500+) and they were blowing speakers.

Hard to blow speakers from too much power, it's clipped input that blows speakers.

Normally you can run about .8 to 1.2 times the RMS power handling of a speaker with no problem. CLEAN signal that is. Now don't go trying to run pink noise or a pure sine at those levels. The crest factor of audio allows you to use more power than normal.

.....Besides, bridging (theoretically) quadruples power into a given load, assuming the power supply is capable of delivering double amperage to each amp channel.

When you double the voltage accross a given resistance, the current also doubles. Since power is equal to voltage times current (P=ExI), the resultant power would be quadruple, again assuming the necessary current is available.

Years ago, I had built a pair of mono amps, the Universal Tigers, from kits, sold by Southwest Technical Products, and featured in construction articles in Popular Electronics. They were rated at 75W/ch continuous. The power supplies were 80V at 3A.

To be able to double power, each would need 80V at 6 amps. Bridging requires two amps per channel, so I figured I'd have all the power I'd need for four amps with 80V at 24 amps. I built a separate chassis for the power supply using a pair of 40V at 25A transformers with the secondaries in series, a 25A block rectifier, and a total of 90,000 µF filtering caps.

Needless to say, the package was more than capable of powering the speakers I had back then: Rectilinear III's, which were very inefficient and rated to accept 100W continuous.

Larry
www.fineelectricco.com