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

[March Audio]

Larger power supply capacitors, or anything else that "stiffens" a power supply, will generally decrease dynamic headroom but provide a bit more steady-state power. Class D amplifiers tend to use regulated power supplies.

However, headroom is just as often (if not more so) a decision made by engineering and marketing as they decide how to spec the device. Ditto things like the ability to "double down", doubling power into 4 ohms from 8 ohms. You can choose to spec higher wattage and less at 4 ohms, or lower 8-ohm wattage but show doubling in power at 4 ohms. Probably more marketing than engineering...

Good points.

My view is that considering the nature of music signals, typically 5:1 peak to rms ratio, the burst levels are far more relevant to real world use. You will be clipping on peaks far before you hit the rms (average) limit of the amp

 

[simbloke]

As far as I can tell, given available internal images, March Audio is the only company that assembles these units correctly. It would be nice to hear if the European and British alternatives actually do account for things such as the pin-1 problem. But it is clear that Alan is on a different level engineering-wise. There are other issues with the VTV amplifiers as noted on other threads but someone like Alan does not need to be explaining the issues to them. While I wish his prices were just a little lower, I understand the fact that he has a business to maintain and that his units are clearly worth the premium.

Indeed. There have been a string of examples on this forum. Badly assembled, incorrectly wired, and same old cases out of China.

The March Audio products look like they are a world away. Worth the money I think. I don't want an electric shock and I don't want my house burning down. (Not particularly referring to VTV at all here)

 

[wwenze]

Thanks for popping in, Alan. We discussed headroom in an older thread here, and I mentioned my Classé Model Seventy with its huge PS capacitors, and I think it has a bit of headroom. I notice that you simply list the NC252MP power specs on your March Audio website without conditions or details, but Amir found that the power ratings by Hypex for the NC252MP were not seriously exaggerated.

As a non-engineer, I get frustrated as you can see from my above post, but now that I have been reminded that Amir tested the IOM version of an NC252MP amp, all of my questions have been answered. According to Amir, the IOM has very limited headroom due to its regulated power supply.

If you offer an NC252MP amp at March Audio, that's a big positive for me, because I know about your passion for high quality and good engineering. And I wouldn't hesitate to buy three of your ultra-low distortion Purifi 400 monoblocks if my budget were bigger.

For the same output power, SMPS require wayyyyyyyyyy less capacitor values than a 50Hz or 60Hz power supply.

Same goes for transformer size.

That's why the world is moving towards SMPS.

"Headroom" is really just a term for "My transformer and semiconductors can only supply 10A, but I want my capacitors to supply 20A for a short period of time".

Oh also, "headroom" and "regulated power supply" are mutually exclusive concepts. Since "headroom" or "temporary power" requires supply voltage to change (usually as the capacitors get depleted), but regulated power supply forces the supply voltage to be constant or it forces a shutdown.
And if we talk in terms of impedance, "headroom" designs use big caps to reduce the impedance at lower frequencies, the bigger the value the lower the frequency. However, regulated power supplies behave like they have virtually zero output impedance at low frequencies all the way to DC.

That said, there are regulated power supplies with so-called "peak power". Usually found bundled with computer casings. But even then the "peak power" is obtained via varying the load, and the "peak power" is a value that is either 1) thermally-related or 2) Lasts for 10us or whatever the switching frequency is, or 3) Whatever value that the space probe found while exploring Uranus.

 

[JustJones]

What you are finding is why I returned my Purifi VTV. Not only were the XLR wired wrong but mine didn't have a mains ground and quite frankly just looked like sloppy workmanship.

 

[jd3]

I considered ordering from VTV as well until I read some of the issues with the assembly. That's the reason I ordered from March Audio.

 

[boggit10]

I really love/hate how all these module sellers only produce power amps...

"Oh, these amp modules have a low input impedance and a varying impedance vs frequency, and hence needs an active preamp stage if you want a volume control? No volume control, problem solved."

Love how they avoid the problem (as opposed to putting a passive volume knob), hate how they avoid the problem.

We do! This is our Auto line level matching Passive TVC/AVC Pre Amp.

 

[stunta]

@boggit10, why are there no specs on your website? For instance, dimensions of the amplifiers? https://www.nordacoustics.co.uk/product-page/nord-three-1et400a-stereo-amplifier

 

[Xulonn]

why are there no specs on your website?

There are lots of pages with specs at the Nord website - just not on the one you linked to.

 

[Xulonn]

The mistakes and sloppy work revealed in this discussion has pretty much eliminated my interest in VTV amps for my upgrade to 3-channels. So I went back to look at the Audiophonics Hypex NC25xMP amplifiers.

[EDIT: Upon further discussion and the response from the owner, I revised my opinion.]

[EDIT2: Audiophonics does not do custom configurations - VTV, however, is a small business with a limited product line, and does.]

I found a good match for my requirements, and have requested a quote for a 3-channel version of the 4-channel HPA-Q250NC. It would use one NC250MP mono module and one NC252 stereo module instead of two stereo modules. I will save a bit on the price, perhaps about $80, which would put it at $825 rather than $905 for the standard 4-channel amp. But it will be exactly the configuration that I want. Three channels amps are rare these days, although Nord also has one which has more features including both RCA and XLR inputs, and is a bit more expensive. Here's the stock 4-channel version from Audiophonics:

 

[Matias]

Apollon has this 3 channel Purifi/NC500 based amp that is just beautiful.

 

[Xulonn]

Apollon has this 3 channel Purifi/NC500 based amp that is just beautiful.

$3,000?? Stop torturing me, Matias - please don't show me things I really admire, but cannot afford.

 

[Xulonn]

But do they account for the pin-1 problem?

That I can easily check and fix. But using information I have learned here, I can ask them to be aware of the issue when I place an order, since it would be a custom build.

 

[stunta]

Apollon has this 3 channel Purifi/NC500 based amp that is just beautiful.

View attachment 62707

I checked the 1ET400A monoblock and its twice the price of the similar one from Nord. Some fancy opamps I guess, but I don't care for those.

 

[kokishin]

For the past couple of years I have used a Parasound Zamp .v3 for my desktop system and enjoyed it. While I have from time to time thought about upgrading it, its size and cool running have kept it in place. Then Amir had to go do his darn test of it. That was enough for me to start poking at new amps. For me it quickly came down to the Schiit Vidar or giving a Class D amp a try. The Vidar was ruled out as being just a bit too large and power hungry (I tend to forget to shut off my amp and the Vidar draws a fair amount of energy at idle). I then started looking at Class D and based on the reviews, Hypex Ncore rose to the top for in the reasonable price stereo camp.

After researching, it came down to four candidates, IOM, March Audio, Audiophonics, and VTV. VTV is an unknown, but popped up when I was searching for hypex amps on Hifishark. It is from Vacuum Tube Values which gets cases made with their logo and then assembles various Ncore Models. I was originally looking at a NC122 but it was $489 while the NC252MP was $499. Same size case, $10 more, twice the power, it was a no brainer.

The VTV showed up last week and I had to let it break in as it was brittle out of the box. Just kidding. I received the VTV this morning. I didn't pull it apart, but the case is nice looking and it appears well assembled. I pulled out my Parasound and replaced it with the VTV. I did have to do a cable swap which put me back $75 as Benchmark was the only company that I could find that wires their RCA to XLR cables according to Hypex's recommendation.

The VTV sounds good to me. I did not do a bunch of back and forth swapping, but it seems to be a bit clearer and relaxed. I am guessing that when turned up the Parasound may have clipped a bit on peaks, while this does not. It is apparent if I turn the VTV way up (louder than I ever listen), it has the ability to overdrive the speakers.

All in all, I would rate the VTV as a great value for a Ncore amplifier. For those wondering, my desktop setup is a Dell Precision workstation running either Roon or Jriver, a Schiit Modi Multibit, Schiit Saga (thanks to their closeout for $200), VTV amp, Totem Mite speakers and a Rythmik L12 sub.View attachment 62550View attachment 62551

Congrats!
Is there a trigger input?
I don't see a trigger input in any of the pics.

 

[boggit10]

@boggit10, why are there no specs on your website? For instance, dimensions of the amplifiers? https://www.nordacoustics.co.uk/product-page/nord-three-1et400a-stereo-amplifier

Just scroll down the page!

 

[CDMC]

After a lot of reading, I have decided that I am going to keep the amp. There is no doubt in my mind that March Audio builds a better designed product with the benefit of higher assembly quality and a front power switch. It also unfortunately costs nearly double shipped to my door and puts it out of my budget, otherwise I would order one. (Please note, I am not accusing March of overcharging, the simple fact is he uses a better case and puts more time into the assembly, along with the cost of shipping from Australia and less than favorable exchange rates, all of which result in a higher cost).

I am also not going to contact VTV about the Pin 1 issue. It appears that cujobob already did this and the response was that it was wired right in accordance with Hypex specs.

https://www.audiosciencereview.com/...ents-of-purifi-1et400a-amplifier.7984/page-73

For the record, VTV is incorrect and March Audio correct. I can see why VTV might be confused with this diagram by Hypex:

https://www.hypex.nl/img/upload/doc/an_wp/AN_Amplifier_signal_wiring.pdf

Even though the diagram can be confusing, Hypex directly deals with the Pin 1 issue and discussed proper wiring:

https://www.hypex.nl/img/upload/doc/an_wp/AN_Legacy_pin_1_problems.pdf

Unfortunately, as others have mentioned, it is not just VTV doing it incorrectly, so does Nord and IOM. It is not helped that the kits sold by Ghent Audio also have the wiring incorrectly. Pin 2 and 3 should not have been inverted on my unit, but at the same time, Nord managed to ship out a unit with the leads flipped on one speaker terminal, a far worse error. Also, the case is now correctly grounded from VTV, unlike a prior poster's example which was not.

In the short term, I have corrected the Pin 2 and 3 being inverted. Longer term, I am going order some new XLR connectors and input board connector and wires and correctly wire up Pin 1. It should cost me less than $30 and then will be correct. I am happy to hear any comments on my proposed placing of the wiring as shown by my terrible drawing in Paint as attached.

 

[stunta]

Just scroll down the page!

That is not the page I linked to. The main page that lists all the amps has the specs. Its strange website design.

 

[CDMC]

Congrats!
Is there a trigger input?
I don't see a trigger input in any of the pics.

Nope, unless you consider your finger on the power switch a trigger.

 

[kokishin]

Nope, unless you consider your finger on the power switch a trigger.

Hardly.

 

[boggit10]

This mistakes and sloppy work revealed in this discussion has pretty much eliminated my interest in VTV amps for my upgrade to 3-channels. So I went back to look at the Audiophonics Hypex NC25xMP amplifiers.

I found a good match for my requirements, and have requested a quote for a 3-channel version of the 4-channel HPA-Q250NC. It would use one NC250MP mono module and one NC252 stereo module instead of two stereo modules. I will save a bit on the price, perhaps about $80, which would put it at $825 rather than $905 for the standard 4-channel amp. But it will be exactly the configuration that I want. Three channels amps are rare these days, although Nord also has one which has more features including both RCA and XLR inputs, and is a bit more expensive. Here's the stock 4-channel version from Audiophonics:

View attachment 62702

All our multi channel amps have a micro controller to sequence start up of modules to avoid high in rush currents and then mute and un mute on start stop to avoid pops, plus a trigger.