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Hypex Ncore NC502MP - audible hum on one channel?

MoreCowBell

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Long time lurker, first time post.

Is it normal to hear an audible hum (only from the right speaker) from the Hypex Ncore NC502MP modules?

I recently purchased a Audiophonics LPA-S500NC, a French made stereo amplifier that utilizes the Hypex Ncore NC502MP module.

My set up is as follows: new MiniDSP SHD --> Audiophonics LPA-S500NC amplifier (via XLR cables) -->pair of new Kef R3 (via Amazon basic 16gauge speaker wire/monoprice banana plugs).

I set everything up and I immediately noticed an audible hum coming only from the right speaker - it sounds like a ground loop. The left speaker has no hum noise. The noise through right speaker is noticeable at 6 inches but barely there at a foot away. Noise disappears from right speaker when I unplug the XLR cable from the amplifier (i tried various xlr cables and different outputs on the SHD but the noise was still there in right speaker only).

The amplifier was returned to Audiophonics. They tested my amplifier and also noticed a low hum in right speaker but said they could only hear it if their ears were right next to the speaker. They also state that this hum is present in ALL of their LPA-S500NC currently in stock. According to Audiophonics this is NOT a defect in the product because 1) i should expect noise in a 500 watt amplifier; 2) the hum is only apparent when they put their ear right next to the speaker.

Perhaps the noise floor is lower in my home compared to their office but how is this not a defect in their amplifiers when there is noise coming from only the right channel on ALL of their amplifiers but not the left??

Is this hum noise on the right channel limited to just Audiophoincs amplifiers or is it present on all Hypex Ncore NC502MP modules? (e.g. March Audio, Apollon audio, etc)

Am i crazy to expect no hum noise on these newish Hypex Ncore amplifiers? I feel like I am being gaslit lol.

Any input would be greatly appreciated!! Thanks.
 

toddverrone

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I have only had experience with ICEpower class D modules, but they were dead silent. No hum, no hiss. I'd expect Ncore to be the same. I definitely think you're being dealt with in a less than honorable fashion.
 

Dundas

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If you have a spare XLR cable try disconnecting the shield from pin 1 at the amplifier end of the cable.
 
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MoreCowBell

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I have only had experience with ICEpower class D modules, but they were dead silent. No hum, no hiss. I'd expect Ncore to be the same. I definitely think you're being dealt with in a less than honorable fashion.
Thank you! That is the sense I was getting but just wanted to confirm...
 
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MoreCowBell

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If you have a spare XLR cable try disconnecting the shield from pin 1 at the amplifier end of the cable.
Unfortunately, I no longer have the amplifier as it was returned to Audiophonics. I tried various XLR cables (monoprice / Hosa) but never tried disconnecting the shield. I don't think its the XLR cables however as the manufacturer also confirmed that they heard noise on the right channel during their tests on all of their identical models..
 

Weeb Labs

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This should be a fairly straightforward situation to resolve. The LPA-S500NC is specified to exhibit an SNR of 124dB. If it falls so far short of that value as to become audible, then it is defective.
 
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MoreCowBell

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Have a look at this document from Hypex:
https://www.hypex.nl/img/upload/doc/an_wp/AN_Legacy_pin_1_problems.pdf

I have 4 channel 252 amp fed by a Marantz AVP that had a hum problem. Lifting the shield ground got rid of the problem. So did disconnecting the mains ground but that is unsafe.

Interesting. I don't believe its the XLR connector because I unplugged the xlr cable from left input (left speaker had no noise) and plugged that same xlr cable into the right input and the same noise occurred.
 

Dundas

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Interesting. I don't believe its the XLR connector because I unplugged the xlr cable from left input (left speaker had no noise) and plugged that same xlr cable into the right input and the same noise occurred.
I am not suggesting that the cable is at fault. It's the ground loop that disconnecting the shield connection breaks. Disconnecting the mains ground also breaks the ground loop but as I said that is unsafe and should only be done as a test.
 
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MoreCowBell

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I am not suggesting that the cable is at fault. It's the ground loop that disconnecting the shield connection breaks. Disconnecting the mains ground also breaks the ground loop but as I said that is unsafe and should only be done as a test.
Got it, thank you for the clarification.
 

Zoomer

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Miami --> Audiophonics ?
Buckeye or VTV not to your taste?
Just curious.
 
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MoreCowBell

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Miami --> Audiophonics ?
Buckeye or VTV not to your taste?
Just curious.
Actually I looked at both but was concerned as to the build quality of vtv and the lack of warranty with Buckeye.
 
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MoreCowBell

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It's a well known grounding issue.
Thanks I was not aware that this issue was well known. Is this grounding issue an issue specific to the amplifier i purchased (i.e. implementation issue of the manufacturer) or is it a general issue affecting all Hypex NCore amplifiers (or the NC502MP module)?
 
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boXem | audio

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Thanks I was not aware that this issue was well known. Is this grounding issue an issue specific to the amplifier i purchased (i.e. implementation issue of the manufacturer) or is it a general issue affecting all Hypex NCore amplifiers (or the NC502MP module)?
It's on all NCxxxMP. They need a clean implementation. The issue was highlighted here when @Amir tested an NC502MP based amplifier.
 

daftcombo

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I have a S500NC from Audiophonics and there is absolutely no hiss/hum in my Aria 906.

To compare, I find the Genelec 8030C a lot noisier 1 meter away. (And JBL 305p MK2 are like a vacuum cleaner.)
 

jtwrace

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I have (4) NC502MP and they're dead silent and have been for the last almost 4 years now. And they've been on 24/7 for that time other than the few times to move them or power outages.
 
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