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Slight Buzz RCA to XLR

Chobes11

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Hi all so I recently purchased a Hypex NC1200 amp and I am getting a slight buzz when everything is connected up. I am going from a Yamaha AVR A1040 Pre out RCA (Chord Anthem 2) to Neutrik RCA to XLR adapter into the amp. I tried getting rid of the jumper and moving the RCA shield to Pin3 leaving Pin1 floating (manuf recommendation) but this made the buzz worse when I plug all the cables back together. I get the same buzz even when only the Neutrik connectors are in. I tried the cheater AC plug trick but it didn’t work either. I’m wondering if I just need to go balanced to get rid of the buzz. Is there a way I can still use my AVR as a source but connect to balanced cables to get rid of the buzz?
Many thanks!
 

ririt

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Please look at this (from March Audio) from another thread: Any issues when pairing Purifi or Hypex class D amps with home cinema AVR

It may help you:

Some general comments, you shouldnt use a RCA to XLR adaptor like this.

index.php



Any noise currents flowing in the RCA screen will be seen by the amp. This is why we dont fit RCA inputs on our amps. You have to use a cable wired as below.

index.php


Fig 3 from Hypex guidence notes

With this configuration the XLR screen is terminated at the far RCA source end. Noise currents flow in the shield wire and not the signal conductors eliminating ground loop based noise issues. Our RCA to XLR cables are configured this way as are the aforementioned Benchmark ones.

Secondly it should be noted the Hypex/Purifi speaker outputs are ground referenced. As such from a measurement perspective it is possible to get noise problems and the AP balanced input should have the same cable config as shown above to again make sure ground currents flow in the shield and not the signal conductors. Using the single ended input could also lead to noise issues for the same ground loop issues.

We often use (as do our customers) RCA single ended sources with our Hypex and Purifi amps and dont hear or measure any noise issues.
 

Panelhead

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I had a buzz a long time ago.
To eliminate some noise maybe ten years ago it required a cheater plug on my video monitor. This was a computer based system. Try different positions that have three prong plugs. Might find it this way.
The converter cable connection diagram above is right. And industry standard. This is what happens with using a TS plug in a TRS jack. Easy balanced to single ended converter.
 
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Chobes11

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Thank you so much! Just ordered the Benchmark cables. I hope it does the trick!
 

waynel

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Thank you so much! Just ordered the Benchmark cables. I hope it does the trick!
Hope they work, depending on the source of the buzz the solution might be different. I just dealt with a ground loop between a Denon 3700H and a benchmark AHB2 when triggering off the AVR, this was solved by not connecting pin 1 to the RCA at all, which is not what Benchmark cables do.
 
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Chobes11

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Hope they work, depending on the source of the buzz the solution might be different. I just dealt with a ground loop between a Denon 3700H and a benchmark AHB2 when triggering off the AVR, this was solved by not connecting pin 1 to the RCA at all, which is not what Benchmark cables do.
Interesting. Yea I took my RCA to XLR adapter apart and removed the jumper from Pin1 to Pin3 and resoldered the shield to Pin3 leaving pin1 untouched. this made the buzzing worse! So I put everything back.
How did you modify the connection to remove pin1?
 

waynel

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Interesting. Yea I took my RCA to XLR adapter apart and removed the jumper from Pin1 to Pin3 and resoldered the shield to Pin3 leaving pin1 untouched. this made the buzzing worse! So I put everything back.
How did you modify the connection to remove pin1?
Not ideal but I used wire cutters to remove the pin one connection and chassis connection from my monoprice cable. I’ll build some better cables soon where I will float the shield at rca end
 

March Audio

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Hi all so I recently purchased a Hypex NC1200 amp and I am getting a slight buzz when everything is connected up. I am going from a Yamaha AVR A1040 Pre out RCA (Chord Anthem 2) to Neutrik RCA to XLR adapter into the amp. I tried getting rid of the jumper and moving the RCA shield to Pin3 leaving Pin1 floating (manuf recommendation) but this made the buzz worse when I plug all the cables back together. I get the same buzz even when only the Neutrik connectors are in. I tried the cheater AC plug trick but it didn’t work either. I’m wondering if I just need to go balanced to get rid of the buzz. Is there a way I can still use my AVR as a source but connect to balanced cables to get rid of the buzz?
Many thanks!

A secondary issue may be that the nc1200 amp is not correctly wired inside. We have seen a number of amps on ASR that are not.

Do a search on "pin 1 problem"

https://www.ranecommercial.com/legacy/note165.html
 

Panelhead

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If pin 1 was not connected in the XLR jack the cable disconnected should not affect the hum level.
Try moving the cheater plug around. Could be something connected to the receiver.
 
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Chobes11

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I am pretty sure it’s wired correctly. Per AES48-19 spec pin #1 grounded to chassis. No buzz when the amp is on with no inputs plugged in. When I plug in the RCA to XLR adapter I get the slight buzz, even when there is no RCA plugged in.
 

zermak

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And just taking a look a Benchmark's XLR to RCA offering I can see two types anyway (with the solution you already tried).
If you are into DIY you could buy a unbal to bal board (like the ones from Neurochrome or Ghentaudio; I use one from Ghentadio for my ICEpower amp and it works perfectly but I can't provide you any measurements of the performance).
 
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Chobes11

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Here is how the ground is wired. Pin1’s connected and then grounded to AC ground through a foot screw.
D3B8B686-4479-4F62-85F6-E127456EA21F.jpeg
834E07E4-7955-4B62-9229-1753D1CE1CAB.jpeg
 
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Chobes11

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March Audio

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I keep seeing different ways that claim to be “correct” wiring. Should the bare wire (red circle) be connected to the chassis separately Instead of Pin1?
Well I have given out advice before but I confess I am becoming less inclined to sort out other manufacturers f ups.
 
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Chobes11

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Well I have given out advice before but I confess I am becoming less inclined to sort out other manufacturers f ups.
I understand. Do you think your RCA to XLR Cables might fix the slight buzz issue?
 

CDMC

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I understand. Do you think your RCA to XLR Cables might fix the slight buzz issue?

It may help, but it doesn’t fix that it is not wired correctly internally. VTV does not seem to understand how to properly do it, despite it being explained. Unfortunately, whoever they are using to assemble these units looks to be getting worse at soldering rather than better.

Look very closely at the diagram in rerit's post (#2 in this thread), as it shows how it should be properly done; as it isn't apparent without looking very closely at the diagram:

1) On the interior of the case, the amp board to the XLR connector, you run pin 2 & 3. The shield does not go to pin 1. It goes to a case ground, with each to a separate ground in the case and as close as practical to the XLR connector, but not connected to it.

2) Pin 1 of the XLR connectors should be grounded to the case at the nearest point possible to where the XLR connector connects to the case. Some XLR connectors have a built in jumper where Pin 1 grounds to case when installed (this is what March Audio uses).

3) The amp and Pin 1 grounds to the case should not be tied together (i.e a star ground). Each should be tied to case separately, so a total of four connections to the case.

The reason this is important is that you are trying to keep noise from getting inside the case to begin with. The pin 1 connection from the source line is supposed to send any emf picked up in the shield to the case. The shield from the amp board is supposed to go to the case, again because you are trying to get any emf out and away from the amp modules. When you wire it the way that VTV has, two things occur. First, you have just routed all the emf picked up by the shield directly into the amplifier and to the board. Second, you have created many more potential ground loop issues.

Most of the time, the improper wiring is not an audibly noticeable issue. The problem is that when it is an audible issue, it is nearly impossible to fix if the wiring isn't does correctly. This is why Rane and AES developed and recommend the AES48 wiring procedure, as it is best practice and eliminates the problem. Unfortunately, many, many, many manufactures do not implement it properly.

If you look at the post I made here, you will see how the XLR wiring looks in the VTV when done in accordance with RANE, AES48, Hypex requirements:

https://www.audiosciencereview.com/...its-all-amirs-fault.13195/page-14#post-467536
 
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CDMC

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They have wired that entirely wrong. Even twisted the speakers wires incorrectly.

Nice touch with the mains wires running right over the voltage regulators.

It is to help give it a nice boost at 60hz.
 

CDMC

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Well I have given out advice before but I confess I am becoming less inclined to sort out other manufacturers f ups.

I don't blame you after doing so and being accused of badmouthing products because you pointed out what needed to be done to correct it.
 
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