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Old 26th November 2012, 05:01 PM   #5641
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Quote:
Originally Posted by robbbby View Post
Can you explain the testing with a shorted input?
No induced ground leakeages or EMI/RFI in the input, minimal impedance noise source for internal noise evaluation.
If any noise remain, you can suspect some internal oscillation problem in the amp itself or noise from the psu.

Last edited by Esperado; 26th November 2012 at 05:04 PM.
 
Old 26th November 2012, 05:05 PM   #5642
Julf is offline Julf  Europe
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Quote:
Originally Posted by ChrisPa View Post
short the input to the power amp
Just make sure you short it at the ends of the input leads or right at the connector - don't use a long jump lead, as it will form a great loop antenna (remember those vertical hula hoops on top of airplanes in old pics?):

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Old 26th November 2012, 08:24 PM   #5643
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Quote:
Originally Posted by Julf View Post
Indeed - with a specified 124 dB SNR, pretty much any noise is an indication of some sort of abnormal issue.
Yes sir!
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Old 26th November 2012, 09:08 PM   #5644
robbbby is offline robbbby  Canada
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Ok, here a couple pictures of the monoblocks I built, hopefully somebody can spot something wrong. Both amps make the same pop and hiss noise.

AMP1

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AMP2

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Old 26th November 2012, 09:32 PM   #5645
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Speaker and PSU cable should be as far from each other as possible.
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Old 26th November 2012, 09:36 PM   #5646
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when you say power supply are you referring to my 120V AC or the multiwire cable that joins the smps to the amp?
 
Old 26th November 2012, 09:41 PM   #5647
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The cable between the SMPS and the amp.
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Old 26th November 2012, 09:42 PM   #5648
robbbby is offline robbbby  Canada
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Ok I rechecked the dc offset stuff, looks like you have to let the amp sit for about 10 minutes since the dc on the input will slowly come down as it warms up.

Next I shorted the inverted/non inverted input conductors. Tweeter still makes the same very faint "pop" noise when powering up/down but now when it is on there is absolutely no white noise or hissing.
 
Old 26th November 2012, 10:17 PM   #5649
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robbbby, whatever they said, try to put a shield between PSU and amp, and shield PSU cables too.
Easy to do just Dirty, for a test, and see if any change.
 
Old 26th November 2012, 11:01 PM   #5650
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what is the best way to "shield the cables? Just wrap them in aluminum foil? Does the shield need to be grounded?
 

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