Hiss and crackle from a Hypex NCore based amp

[paulzhere]

Hi

I purchased this Hypex NCore power amp HPA-S500NC 2x500W @4ohm from Audiophonics in 2022.

This amplifier has developed a hiss and crackling noise which I think is not normal. When I bring my ear a few centimeters from the tweeters of my speakers, I can hear this noise. But when I connect my same speakers with the same cables to my Emotiva BASX A300 power amplifier, the noise is much lower. Of course, there's a faint hiss but not as bad as this Audiophonics amp. This surprises me because it is based on a hypex module which should have a noise floor way lower than the Emotiva amp. It should be virtually quiet. I have recorded this noise and I try to attach it here as a zip file. Thanks for any help and support.

Cheers
Paul

 

[Golfx]

Hiss might be a gain mismatch between your AV processor and your amp=higher the gain the louder the hiss. Plus speakers with higher efficiency tend to hiss more when using high gain AVPs.

Does your amp offer adjustable gain settings? I am not familiar with audiophonics‘ reputation. I have had Nord, March and Apollon Hypex/purifi monoblocks and multi8 amps and have had zero, zero, hiss.

 

[PENG]

Hiss might be a gain mismatch between your AV processor and your amp=higher the gain the louder the hiss. Plus speakers with higher efficiency tend to hiss more when using high gain AVPs.

Does your amp offer adjustable gain settings? I am not familiar with audiophonics‘ reputation. I have had Nord, March and Apollon Hypex/purifi monoblocks and multi8 amps and have had zero, zero, hiss.

But he said "This amplifier has developed a hiss and crackling noise which I think is not normal. ". and he bought it in 2022. That seems to imply it didn't have that hiss and crackling in the beginning and we don't know when it "has developed.." So, it may just have developed a defect, could even be some loose connections such as in the grounding scheme, and/or loose connections to the I/Os, best bet is to email Audiophonics. I read some posts by at least one or two of their customers, that they did get reasonably good support, that is iirc..

 

[paulzhere]

Thanks for your valuable inputs @Golfx and @PENG . I have an update. I have found the source of the issue and it is the source (pun not intended). I removed the all the inputs and turned on the amp and it is indeed dead silent (as @Golfx mentioned) even though I have quite sensitive speakers - 92dB. I was thus assured that the issue is not with the amp. The amp is fed from a MiniDSP Flex RCA which I recently acquired and this seems to be the problem. Previously I was using a MiniDSP 2x4 HD which didn't seem to have this issue. I upgraded to the Flex to have a lower noise floor and better sampling rates to play with, but ironically it seems to have backfired. This is counterintuitive because the Flex has been measured at ASR to have a much higher SNR than the original 2x4 HD. So I ask myself if my unit is faulty. I purchased it used from a second-hand website here in France. I need to get hold of the guy and ask him if he has the invoice. What is intriguing is that the crackling is very rhythmic... If you listen to the attached recording, it is like 3 crackles per second which gives us a frequency in the ballpark of 180 hz. I wonder if there is something else nearby which is emitting such a frequency. But then why was the 2x4 HD not effected by this?

I already contacted Audiophonics about the issue and they promptly replied asking me to disconnect all the sources from the amp and then test again (which I did). I will come back with further updates, if any.

Best
Paul