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Old 27th April 2005, 12:09 AM   #1
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Default strange noise from right channel

Hi All!
I've got a problem with my hifi. My system is an actively biamped 3-way system. I use an integrated amp (NAD C370). Its pre-amp part leads to a Behringer cx 3400 crossover. From there the mids and highs go to the poweramp part of the NAD, the low end goes to a JB Systems AX400 poweramp.
The system has always worked fine. Yesterday I discoverd a strange kind of noise from the midrange driver of the left speaker. The noise is not loud, but audible when about 1 meter from the speaker (about 3.3 feet). It sounds like a beep, with some kind of cracks in it, and the frequencie constantly changes but with small steps. Guess the frequencies are somewhere between 500 and 800 hz.
I tried a few things to find out what causes this noise. I switched powerams (used the NAD to drive the lows, the JB Systems to drive mid/high), now the noise came from the woofers.
Switched cables that go from Crossover to both poweramps, but these were also not at fault.
Tried the NAD used as a complete integrated amp on my dads B&W CDM 9 NT (with passive crossovers): No noise.
The noise is still there when the Behringer is turned off. Strangely it disappears when I pull the powercord out of the behringer!
What could cause this noise? Is there something wrong with the NAD?
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Old 27th April 2005, 09:28 AM   #2
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anyone?
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Old 27th April 2005, 09:32 AM   #3
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Swap left and right inputs to the NAD from the crossover and see if the problem moves side.
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Old 27th April 2005, 09:33 AM   #4
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I've already done that: problem stays on right side only
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Old 27th April 2005, 09:39 AM   #5
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Sounds like the amp is faulty then. Sorry.

:edit: Quick thought- you have swapped out the signal and speaker cables haven't you?
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Old 27th April 2005, 09:49 AM   #6
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Quote:
Originally posted by pinkmouse
Sounds like the amp is faulty then. Sorry.

:edit: Quick thought- you have swapped out the signal and speaker cables haven't you?

yes.
Any idea what it might be? The amp works perfectly well in configuration with my dads' B&W's with passive crossover...
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Old 27th April 2005, 11:06 AM   #7
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If the NAD is a DC coupled amp, could be a combination of DC offset from the Behringer and the NAD DC response. Switching of the Behriner might cause the signal to be cut but the DC offset to remain. Switch L-R on the Behringer and see if the noise switches also.

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Old 27th April 2005, 11:20 AM   #8
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I've already tried that, but the noise remains on the right channel..
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Old 27th April 2005, 11:38 AM   #9
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I don't know the amp, but the obvious thing is to open it up and check that you have no dry joints on the connectors, and if the input uses electrolytics as DC blockers then replace them.
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Old 27th April 2005, 12:17 PM   #10
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I'm not too good with electronics... Is it hard to DIM, or should I have a professional do it. How do I check if its actually those DC blockers? Is that the only thing that may be broke?
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