VTV Hypex Ncore NC252MP (It's all Amir's fault)

[rebbiputzmaker]

You're conflating two different problems. Not following AES48 opens up the possibility of ground loop problems, which can be quite audible even with line level interconnects. Starquad cable provides extra immunity from local magnetic fields relative to twisted pairs. Both are often heard as 'mains hum' which may be where the confusion comes from.

I am well aware of the difference, not confused at all I just mentioned that so people who might not be aware of the benefits of Starquad and concerned about noise and interference will be aware and might decide to use that as their cabling.

 

[rebbiputzmaker]

I'm an engineer, but not an EE. Every time I think I understand the ground loop issue in connecting an unbalanced source to a balanced amp, I read something else that tells me I don't get it.

I want to buy an NC252MP-based amp, but I have both balanced and unbalanced sources that I would like to use, or at least, evaluate. Hence, I plan to buy an amp with balanced inputs.

For years, I thought the diagram on the Rane page was the end of the story, so to speak, as the article references AES48. Connect the shield to pin 1 on the male XLR that plugs into the female XLR and do not connect the shield to the shell of the RCA on the source end, as per https://www.ranecommercial.com/kb_article.php?article=2107 :

View attachment 62847

But then I see this on page 17 of the app notes for the Hypex NC400 module:

View attachment 62849


That shows the shield on the balanced cable connected on both ends. However, there is a caveat that I highlighted in yellow:

"Assuming that the RCA shell on the source is bonded to the chassis, ..."

That implies to me that if the RCA shell is not bonded to the chassis, then the shield should likewise not be connected to the shell of the RCA plug.

If I build a single set of RCA-to-male XLR cables, should I leave the shield unconnected to the shell on the RCA? What can happen if the cable shield is connected to the RCA shell, but the RCA shell is not bonded to the chassis? Is there something about the Hypex modules that is different from any other power amp when it comes to how they should be interfaced with unbalanced sources?

Thanks.

I have used hypex amps with both balanced and unbalanced sorces with no problem at all. I have used RCA to XLR adapters and even unshielded cables, no ground at all everything floating never had any issues. There can be instances of ground noise but probably very rare. Sometimes connecting two devices with different ground potential can cause problems also. There is not one perfect answer. I just think this is rather overblown in an attempt to prove vtv is not a good purchase choice. I’m not a customer at all but he seems to actually be an honest reliable person with a long established business and offers both money back and a two year warranty. Doesn’t sound like a great deal of risk IMO. Since he also advertise his custom work, just ask him to wire it the way you want, that would be the solution.

 

[CDMC]

Just one comment, don't take new wires from pins 3 and 14 of the idc connector to chassis, just take the braids that are currently connected to pin1 on the xlrs to chassis.

Thanks. Will do. It really is kind of you to help with this given it is a (sort of) a competitor's product.

 

[sejarzo]

To be honest, I was thinking about VTV and traded a few emails with him, but the construction simply looks way too messy. Right now, my preference is to buy one from Audiophonics, as the price including shipping (but free of VAT for a US buyer) is less and the pictures I have seen of the construction look far better.

My post is more about my confusion over Rane's diagram, which claims it is best practice for interfacing components per AES48, versus the Hypex diagram, which is obviously not the same.

I just checked the two unbalanced DACs that I have, and while both of them have PCB mounted RCA's that appear to have a gap between the shell side and the chassis, my DMM shows continuity between the shell side and the hex bolts that fasten the back panel to the rest of the anodized case. Thus my question might be moot in my particular situation, but I do want to understand what the truly best practice is, and why.

 

[rebbiputzmaker]

As mentioned, there are other issues as well including the use of that IEC filter. You can find a good discussion starting here: https://www.audiosciencereview.com/...ents-of-purifi-1et400a-amplifier.7984/page-72

Yes I have read that and again a bit much, but that’s my opinion. For another manufacture to say that the XLR ground not being connected could be dangerous is ridiculous. I don’t see an issue with the iec filter either, or the shell being used as ground to chassis. Push on connectors are friction fit also, so a proper friction fit to a chassis can work. If you don’t want the filter just tell him. Seems on subsequent amps he wired it. Also since this is a custom build, people can just ask for what they want. There are many choices out there and I really do not see much difference between them other than cost availability and location. I would think one will be happy listening to any of the amps that we are talking about no matter who built them.

 

[Xulonn]

I just think this is rather overblown in an attempt to prove vtv is not a good purchase choice.

Please stop with the phony value judgements. No one is "trying to prove" anything - we're just commenting on a commercial kit-builder's assembly skills and attitude towards craftsmanship and quality. That's what audio hobbyists often do on internet forums. There are also professionals here who take pride in their workmanship are, in my opinion, entitled to criticise sloppy assembly. That cobbled rectangular connector with the duct tape around it and the appearance of some of the soldering joints are a turnoff for me - I don't like sloppy workmanship. If you don't care about craftsmanship and pride in workmanship, go for the shoddy stuff. But it is just not something that many of us enjoy or want to promote.

There is nothing unique about this product, but the price is good, the module is good, it's made in the U.S. and shipping is free. Plus I like the simple faceplate with a cool logo machined into it. But for a similar price or perhaps a bit more, why not buy from a person or company that takes pride in their craftsmanship and tries to do things right? What's wrong with owning a component that looks good inside and out in addition to performing well? (Especially for personal and not professional use.)

 

[DonH56]

I'm an engineer, but not an EE. Every time I think I understand the ground loop issue in connecting an unbalanced source to a balanced amp, I read something else that tells me I don't get it.

I want to buy an NC252MP-based amp, but I have both balanced and unbalanced sources that I would like to use, or at least, evaluate. Hence, I plan to buy an amp with balanced inputs.

For years, I thought the diagram on the Rane page was the end of the story, so to speak, as the article references AES48. Connect the shield to pin 1 on the male XLR that plugs into the female XLR and do not connect the shield to the shell of the RCA on the source end, as per https://www.ranecommercial.com/kb_article.php?article=2107 :

View attachment 62847

But then I see this on page 17 of the app notes for the Hypex NC400 module:

View attachment 62849


That shows the shield on the balanced cable connected on both ends. However, there is a caveat that I highlighted in yellow:

"Assuming that the RCA shell on the source is bonded to the chassis, ..."

That implies to me that if the RCA shell is not bonded to the chassis, then the shield should likewise not be connected to the shell of the RCA plug.

If I build a single set of RCA-to-male XLR cables, should I leave the shield disconnected from the shell on the RCA? What are the potential downsides if the cable shield is connected to the RCA shell, but the RCA shell is not bonded to the chassis? Is there something about the Hypex modules that is different from any other power amp when it comes to how they should be interfaced with unbalanced sources?

Thanks.

It is somewhat circuit-dependent and Rane's diagram is the more general use case while Hypex is showing a very specific case for their amplifiers. It also depends which way the signal is going. RCA output to XLR input often leaves the shield (pin 1) floating at the receiving end (by convention, could be either end) and connects the RCA "ground" (may or may not be chassis ground) to the inverting (-) XLR input. By that convention, I would leave the shield connection at the amplifier end of the Hypex cable floating. Normally what I have done in the past is to connect the shield at both ends and, if there is hum, lift it at the receiving (amplifier, XLR) end.

For outputs, it is somewhat common to leave the inverting XLR output floating, rather than shorting an output driver to ground.

In practice you often have to try a couple of things if you have noise or a ground loop. There are a number of ways to implement a balanced connection and some schemes work better than others.

FWIWFM - Don

 

[rebbiputzmaker]

It is somewhat circuit-dependent and Rane's diagram is the more general use case while Hypex is showing a very specific case for their amplifiers. It also depends which way the signal is going. RCA output to XLR input often leaves the shield (pin 1) floating at the receiving end (by convention, could be either end) and connects the RCA "ground" (may or may not be chassis ground) to the inverting (-) XLR input. By that convention, I would leave the shield connection at the amplifier end of the Hypex cable floating. Normally what I have done in the past is to connect the shield at both ends and, if there is hum, lift it at the receiving (amplifier, XLR) end.

For outputs, it is somewhat common to leave the inverting XLR output floating, rather than shorting an output driver to ground.

In practice you often have to try a couple of things if you have noise or a ground loop. There are a number of ways to implement a balanced connection and some schemes work better than others.

FWIWFM - Don

Thank you very much Don. Experience is much better than supposition.

 

[sejarzo]

Thanks, Don. I was planning to re-purpose some Mogami 2534 starquad RCA-to-TS cables that I no longer need that already have the shield connected on the RCA end.

 

[Xulonn]

For another manufacture to say that the XLR ground not being connected could be dangerous is ridiculous.

Your b.s. is ridiculous. Please stop! Why are you spewing this misinformation?

I searched all five pages of this thread as well as the page of the Purifi review that you linked to, and you are the only one to use the word "dangerous"! The only manufacturers commenting in this thread are March Audio and NOrd Acoustics. I looked at all of their posts, and could not locate any comment where one of them implied - much less stated - that there is anything "dangerous" about the XLR wiring, errors.

In reading this thread, it is obvious even to a non-engineer like me that for hum and noise control via grounding, there are several options for XLR connector - and none of the options discussed are dangerous.

 

[rebbiputzmaker]

Your b.s. is ridiculous. Please stop! Why are you spewing this misinformation?

I searched all five pages of this thread as well as the page of the Purifi review that you linked to, and you are the only one to use the word "dangerous"! The only manufacturers commenting in this thread are March Audio and NOrd Acoustics. I looked at all of their posts, and could not locate any comment where one of them implied - much less stated - that there is anything "dangerous" about the XLR wiring, errors.

In reading this thread, it is obvious even to a non-engineer like me that for hum and noise control via grounding, there are several options for XLR connector - and none of the options discussed are dangerous.

a screenshot.

 

[sejarzo]

You are are taking March Audio's comment out of context. His "dangerous" comment refers to a faulty "mains earth connection" as the ground pin of the IEC power inlet is not connected to the chassis, and the construction otherwise doesn't follow standard safety considerations.

See his original post that states that very clearly!

https://www.audiosciencereview.com/...fi-1et400a-amplifier.7984/page-72#post-378521

 

[rebbiputzmaker]

...arguments for argument's sake.

 

[sejarzo]

I like the use of "earth" (most typically in non-US English) to refer to mains/AC power concerns and "ground" when referring to signal, which IMHO makes the distinction more clear.

 

[Xulonn]

a screenshot.

You are are taking March Audio's comment out of context. His "dangerous" comment refers to a faulty "mains earth connection", as the ground pin of the IEC power inlet is not connected to the chassis and the construction otherwise doesn't follow standard safety considerations.

See his original post that states that very clearly!

https://www.audiosciencereview.com/...fi-1et400a-amplifier.7984/page-72#post-378521

Thanks @sejarzo. I don't know what Putzmaker's motivation is, but he is apparently not a fan of good quality workmanship and craftsmanship. And thinking that a REALLY BIG, in-your-face font sizes make misleading and out of context quote true is troubling - and doesn't add any credibility to his weak position.

But let me ask you directly, Putzmaker: Why do you defend shoddy workmanship with such fervor? Do you have a relationship with the people (person?) at VTV?

 

[CDMC]

You are are taking March Audio's comment out of context. His "dangerous" comment refers to a faulty "mains earth connection" as the ground pin of the IEC power inlet is not connected to the chassis, and the construction otherwise doesn't follow standard safety considerations.

See his original post that states that very clearly!

https://www.audiosciencereview.com/...fi-1et400a-amplifier.7984/page-72#post-378521

AND TO BE ABUNDANTLY CLEAR, THE UNIT I RECEIVED, THAT IS THE SUBJECT OF THIS THREAD, HAS THE MAINS PROPERLY GROUNDED TO THE CASE.

 

[sejarzo]

Thanks @sejarzo.

You are welcome. I am savvy enough to grasp that "dangerous" almost certainly refers to high voltage AC concerns/poking around charged caps, and only rarely to something that is "dangerous" in the sense of sending DC or otherwise improper signals out of an amp that ruin speakers.

 

[CDMC]

Thanks @sejarzo. I don't know what Putzmaker's motivation is, but he is apparently not a fan of good quality workmanship and craftsmanship. And thinking that a REALLY BIG, in-your-face font sizes make misleading and out of context quote true is troubling - and doesn't add any credibility to his weak position.

But let me ask you directly, Putzmaker: Why do you defend shoddy workmanship with such fervor? Do you have a relationship with the people (person?) at VTV?

It doesn't appear he is defending it with a fervor, he is parsing out the difference between a safety issue and a quality control issue. Is the quality the best, no. But for the price, it is reasonable. We have seen worse work in far higher priced items. For $23 I have an entire wire and connector assembly coming from Ghent and for another $8, I will use high quality Neutrik face plate XLR's and correct the wiring. For the price invested, I am more than happy.

 

[rebbiputzmaker]

Thanks @sejarzo. I don't know what Putzmaker's motivation is, but he is apparently not a fan of good quality workmanship and craftsmanship. And thinking that a REALLY BIG, in-your-face font sizes make misleading and out of context quote true is troubling - and doesn't add any credibility to his weak position.

But let me ask you directly, Putzmaker: Why do you defend shoddy workmanship with such fervor? Do you have a relationship with the people (person?) at VTV?

I really rather not continue this but it is rather funny. Big font size? Motivation? Life is too short stay safe. And it is still safe to drink corona beer don’t worry.

 

[Hemi-Demon]

AND TO BE ABUNDANTLY CLEAR, THE UNIT I RECEIVED, THAT IS THE SUBJECT OF THIS THREAD, HAS THE MAINS PROPERLY GROUNDED TO THE CASE.

Can you post a picture of your received item? Also does your amp also have grey electrical tapw in the main ppwr connecto

Your b.s. is ridiculous. Please stop! Why are you spewing this misinformation?

I searched all five pages of this thread as well as the page of the Purifi review that you linked to, and you are the only one to use the word "dangerous"! The only manufacturers commenting in this thread are March Audio and NOrd Acoustics. I looked at all of their posts, and could not locate any comment where one of them implied - much less stated - that there is anything "dangerous" about the XLR wiring, errors.

In reading this thread, it is obvious even to a non-engineer like me that for hum and noise control via grounding, there are several options for XLR connector - and none of the options discussed are dangerous.

Semantics, but "potentially dangerous" does not defame another manufacturer. MarchAudio is simply trying to help people. At least MarchAudio is giving help for wiring improvements out to people for FREE. Why attack the messenger and not the builder?

AND TO BE ABUNDANTLY CLEAR, THE UNIT I RECEIVED, THAT IS THE SUBJECT OF THIS THREAD, HAS THE MAINS PROPERLY GROUNDED TO THE CASE.

Can you post a picture of your received item? Also does your amp also have grey electrical tape wrapped around the main molex connector to the board?