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Pop/crack on power up, followed by audible tweeter hiss

Hey there, looking for a little advice before throwing money at this issue. I recently installed an integrated amp (nuprime ida-8) in my 2.1 system. When I power up the amp I get a pretty loud pop/crack noise from the speakers followed by a hissing noise from the tweeters that's quite obvious near the speaker and just audible from my listening position. This happens regardless of input, mute toggling, and is independent of the volume level. The amp is plugged directly into the wall (tried multiple outlets). I've been googling, and ruled out some things:

-Disconnected everything on the amp other than power and the l/r speakers
-Unplugged everything else in the house, shut lights off etc
-Made sure the speaker wires weren't touching anything
-Tried two different amplifier units
-Tried 'cheater' plug on the amp power cord

None of this had any effect. Previously I had a pure class-d integrated for a time that was dead silent. I'm in a fairly old apartment building so I don't have any control over the wiring. Is the next step to think about power conditioners or some other device? Any input appreciated. Thanks. 
artishard116
artishard116 OP
4 posts
 
From what I understand it's actually a class A/D hybrid. The previous integrated I was using (NAD 7050) was pure class D and was completely silent on startup and made no audible noise at max volume with nothing playing. 
georgehifi's avatar
georgehifi
10,312 posts
 

The hiss noise is not volume control dependent on class D’s, which means it does not emanate from the gain stage.

It’s there on some that have too higher set a final roll/off filter, eg flat to 20khz or more. And this lets through the switching noise through to the speakers which is heard as hiss from the tweeters.

The Nad may have filtered it out by setting the final roll/off filter lower (<20khz), and thus subdue the hiss much more.

BTW I had to replace both tweeters on the Wilson 8’s (which weren’t cheap) as both were severely compromised after all that constant punishment over time, needless to say he got rid of the ClassD monoblocks after that, and purchased a good linear amp.

Once the technology is available in the near future to get the switching frequency 3 or more times higher than it is now to say 2 megahertz or more then the output filters can do the right job without getting too close to the audio band and effecting it with early HF roll off and phase shift, as it will be able to be done well away from the audio band and leave it untouched.

Cheers George

artishard116 OP
4 posts
 
Thanks for the response. So you're saying it's normal for a class-D? This is all a bit over my head but it seems odd none of the reviews I've read mentioned anything similar. I assumed it was something specific to my setup/room. 
georgehifi's avatar
georgehifi
10,312 posts
 

Not normal for all Class D's (  it depends on filter cutoff frequency), but some that I have had experience with yes.

And for yours I can't tell unless I had it on the test bench, but it sure sounds like it, as what you describe has all the hall marks.


Cheers George

artishard116 OP
4 posts
 
Good to know, thank you. 
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