Slight Buzz RCA to XLR

[Chobes11]

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

What about this wire that is just in the air? Should that be connected to a ground as well?

 

[CDMC]

What about this wire that is just in the air? Should that be connected to a ground as well?

No clue what that is, it is not part of the standard hookup, which should be hot, inverted, ground.

 

[Chobes11]

@CDMC
Thanks for the pictures. Here is what I got so far. I tried to do everything without ordering parts or modifying it too much in case I need to put it back to how I got it.
I connected Pin1 to the mounting screw of the XLR jack.
when I connected everything I still got a little buzz but I think it is my RCA to XLR adapter. So I think I’m going to leave it like this and see if the new cables help.

 

[Chobes11]

No clue what that is, it is not part of the standard hookup, which should be hot, inverted, ground.

If you look at the green circle there is a 4th wire on the amplifier board. But is that supposed to go to case ground too?

 

[CDMC]

If you look at the green circle there is a 4th wire on the amplifier board. But is that supposed to go to case ground too?
View attachment 77344

That is the NC400. It looks like a turn on lead to jumper from that connector (J6) to J2. See page 7:

https://www.hypex.nl/documenten/download/1848

 

[CDMC]

@CDMC
Thanks for the pictures. Here is what I got so far. I tried to do everything without ordering parts or modifying it too much in case I need to put it back to how I got it.
I connected Pin1 to the mounting screw of the XLR jack.
when I connected everything I still got a little buzz but I think it is my RCA to XLR adapter. So I think I’m going to leave it like this and see if the new cables help.

That looks good with two caveats (and understanding these are not an option at the moment):

1) Without sanding the anodizing, you may not be grounded.
2) Shortening the green wires would be good.

The cables should help.

 

[Chobes11]

i did the recommendation, no noticeable change on the buzz. The new cables arrive Friday, I’m hoping they help...
On another note, I‘ve been listening to music on low to medium volume for 4 hours and the top of the case is 106 deg F. I think it might have felt hotter before the recommendations were done. Is this temperature normal for the SMPS3KA700?
for comparison my Yamaha A1040 which I’m using as a preamp is 101F.

 

[Chobes11]

Just got the Benchmark cables. They feel and sound great for the price and the best part is...THE BUZZING WENT AWAY! Now all I hear is a faint hiss with my ear up to the tweeters which I am totally cool with. thanks everyone for your help, I have learned a lot about wiring and ground loops. Those RCA to XLR adapters are not wired properly for this application.
As for the temperature, I think it is normal for nCore based on some thermal images that I have seen, like the one nCore on the bottom of the image (an NC500?) reached about 140 deg F. I will take my lid off for a better comparison but I am less worried now. For now I am going to sit down and enjoy the amp

 

[CDMC]

Hurray. Glad that fixed your issue.

 

[RayDunzl]

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

Too bad there aren't any common tunings that would take advantage of that.

https://pages.mtu.edu/~suits/notefreqs.html

 

[CDMC]

Too bad there aren't any common tunings that would take advantage of that.

https://pages.mtu.edu/~suits/notefreqs.html

B1 on a 432 scale gets you pretty darn close. Just get everyone to return to that scale and play slightly flat and you are good to go.

 

[Veri]

Gotta agree on the benchmark cables, love those Rean connectors and overall, benchmark makes great stuff. even cables

 

[Henry666]

Hello to all. I am new here and having some problems with an acquired nc252mp here in Germany. I have read through the numerous posts regarding the grounding of xlr and the use of xlr to rca cables. I believe I wired everything correctly and bought the monoprice xlr to rca cable recommended by several people. Unfortunately when I hook uo the amp to the preouts of my argon audio sa1 all I here is loud feedback/ground loop and no music. I have installed the ncore in a plastic case. Could that be the problem with grounding issues? Any suggestions, answers and or critique welcome. Thanks.

 

[Chobes11]

If the case is not conductive, how is everything grounded? If it’s not THE problem is likely is A problem

 

[Henry666]

Thanks for the reply. Is a plastic case not useable? Could I make it conductive somehow? More inportantly is the mains ground doing what it should?

 

[Chobes11]

Thanks for the reply. Is a plastic case not useable? Could I make it conductive somehow? More inportantly is the mains ground doing what it should?

Quickly looking on DIYaudio.com people use alternative case material. Maybe the question is better suited there. its hard to tell by the picture but your Right channel XLR might wired incorrectly. It looks like the red ground wire is not connected to Pin1.