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Internal ground loop in Apollon NCMP6350 (Hypex NC502MP)

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audioBliss

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May 7, 2019
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I got the amp back today and I plugged it in to my balanced pre-amp with the Sommer XLR cables. Dead silent in all speakers.

TL;DR - Use NCxxxMP modules with balanced pre-amp or be prepared to make an effort in getting the cables setup just right. Nothing I was prepared for but in my case it worked out just fine since I happened to switch pre-amp recently to a balanced one. Basically if you're getting high pitch buzz in the speakers your amp is most likely just fine and cables need to be looked at. It feels really good to know this for a fact and the reasons are described in this thread.

Hopefully this thread will be useful for other owners of these amp modules(I assume it will be the same regardless of manufacturer) that are using them with an unbalanced pre-amp. Thank you everyone for helping me solve the mystery and @Apollon Audio thank you for the detailed input and measurements from your side.
 
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Panelhead

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Apr 3, 2018
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Seems the answer is always use a balanced source and cable.
 

Chaos01

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Joined
Aug 24, 2023
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I got the amp back today and I plugged it in to my balanced pre-amp with the Sommer XLR cables. Dead silent in all speakers.

TL;DR - Use NCxxxMP modules with balanced pre-amp or be prepared to make an effort in getting the cables setup just right. Nothing I was prepared for but in my case it worked out just fine since I happened to switch pre-amp recently to a balanced one. Basically if you're getting high pitch buzz in the speakers your amp is most likely just fine and cables need to be looked at. It feels really good to know this for a fact and the reasons are described in this thread.

Hopefully this thread will be useful for other owners of these amp modules(I assume it will be the same regardless of manufacturer) that are using them with an unbalanced pre-amp. Thank you everyone for helping me solve the mystery and @Apollon Audio thank you for the detailed input and measurements from your side.
Did your speakers still Buzz when you use the unbalanced AVR?
Got the Same Problem and wont buy a balanced pre amp, will use my avr with rca.
Whats the solution now for this Case ?
 
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