Review and Measurements of Hypex NC400 DIY Amp

[Dnuos]

Greetings,
I'm new to this forum but have been using a pair of NC400/SMPS600-V3 mono-amp for a few years. One of the 2 did not turn on recently after a year of being unused. The fuse is not open. The caps and coils appear to be intact. The row of LEDs located in the middle of the NC400 module blinks once every 2 seconds. I've written to Hypex but haven't got any reply yet. I hope someone here can point me to the resource to troubleshoot the issue, even replacing the faulty amp or PS module. I apology if this is not the place for these type of query.

Thanks in advance for your time and help.

hi try posting this question in EEVBLOG along with some photos of the board.

 

[anphex]

Quick question about the switchting frequency. Since it is about 460khz, does it mean that the amp could well reproduce 384khz sampled audio? Or do the 460khz have to be divided by two because you need a full on and off switch to generate the pulse?

 

[Julf]

Quick question about the switchting frequency. Since it is about 460khz, does it mean that the amp could well reproduce 384khz sampled audio? Or do the 460khz have to be divided by two because you need a full on and off switch to generate the pulse?

Audio sampled at 384 kHz would only contain frequencies up to 192 kHz, but unless you are a bat, who cares?

 

[anphex]

Audio sampled at 384 kHz would only contain frequencies up to 192 kHz, but unless you are a bat, who cares?

Dang, you got me.

No seriously, just wondering how you derive the maximum khz resolution a class d amp can handle from the switchting frequency. So I am just going to assume it is swichting frequency / 2.

 

[boXem]

Dang, you got me.

No seriously, just wondering how you derive the maximum khz resolution a class d amp can handle from the switchting frequency. So I am just going to assume it is swichting frequency / 2.

Power bandwidth x 2 is a better estimate batman

 

[anphex]

This doesnt get out of my head.
So considering we have a Monoblock of NC400, wouldn't that make it it a 5 Watt SINAD of about 130 dB if the noise floor is at about -140? I am trying to make a final verdict between AHB2, 1ET400A Purifi and the NC400 regarding price/performance value.

1ET400A and NC400 look about the same spec wise, so I don't see any drawbacks when choosing on or there other, it's mostly preference. Though NC400 has the DIY kit and requires almost no know how to build. Also I see that the AHB2 achieved that SINAD of about 112 with the low gain setting and 9db gain, so it looks like there was plenty of gain sacrificed to achieve higher sinad.
Just trying to extrapolate the NC400 monoblock data to make a comparision of my current setup vs. AHB2.

 

[boXem]

View attachment 143082

This doesnt get out of my head.
So considering we have a Monoblock of NC400, wouldn't that make it it a 5 Watt SINAD of about 130 dB if the noise floor is at about -140? I am trying to make a final verdict between AHB2, 1ET400A Purifi and the NC400 regarding price/performance value.

1ET400A and NC400 look about the same spec wise, so I don't see any drawbacks when choosing on or there other, it's mostly preference. Though NC400 has the DIY kit and requires almost no know how to build. Also I see that the AHB2 achieved that SINAD of about 112 with the low gain setting and 9db gain, so it looks like there was plenty of gain sacrificed to achieve higher sinad.
Just trying to extrapolate the NC400 monoblock data to make a comparision of my current setup vs. AHB2.

You see the noise floor at -140 dB, but it is not. Type "FFT gain" in your favorite search engine. Basically you will see that you can't conclude anything from this graph without knowing the FFT size.
I do not have all the NC400 perf in mind. If I remember well, it's THD is a bit higher than the 1ET400A, noise about the same. In both cases, their SINAD is noise dominated. 1ET400A and ABH2 have about the same THD, lower noise for the ABH2 => better SINAD (and still noise dominated).

 

[Feyire]

1ET400A and NC400 look about the same spec wise, so I don't see any drawbacks when choosing on or there other, it's mostly preference. Though NC400 has the DIY kit and requires almost no know how to build. Also I see that the AHB2 achieved that SINAD of about 112 with the low gain setting and 9db gain, so it looks like there was plenty of gain sacrificed to achieve higher sinad. Just trying to extrapolate the NC400 monoblock data to make a comparision of my current setup vs. AHB2.

Even though the NC400 measures exceptionally well, it is unfortunately sonically flawed due to hysteresis caused by the iron core inductor in its LC filter.

Just like with the ABH2, you can also lower the gain on the NC400 in order to achieve an even lower noise floor, but in the case of the NC400, this is more difficult, as it requires physical removal of an SMD resistor on the board.

So in my opinion, the 1ET400A is the clear price/performance champion.

 

[Julf]

Even though the NC400 measures exceptionally well, it is unfortunately sonically flawed due to hysteresis caused by the iron core inductor in its LC filter.

Do we have any objective evidence that the difference is audible?

 

[anphex]

Even though the NC400 measures exceptionally well, it is unfortunately sonically flawed due to hysteresis caused by the iron core inductor in its LC filter.

Just like with the ABH2, you can also lower the gain on the NC400 in order to achieve an even lower noise floor, but in the case of the NC400, this is more difficult, as it requires physical removal of an SMD resistor on the board.

So in my opinion, the 1ET400A is the clear price/performance champion.

What drawbacks does that hysteresis have?

 

[simbloke]

Even though the NC400 measures exceptionally well, it is unfortunately sonically flawed due to hysteresis caused by the iron core inductor in its LC filter.

Eh? What is this flaw that does not show in the measurements?

 

[Julf]

What drawbacks does that hysteresis have?

Theoretically slightly higher nonlinear distortion (but the SINAD is limited by noise, not distortion) and a tiny bit of loss of efficiency.

 

[Feyire]

Do we have any objective evidence that the difference is audible?

Certainly:
Purifi Audio - A Straight Wire to the Soul of Music
This Thing We Have About Hysteresis Distortion
Combating Hysteresis Distortion (part 1: Amplifiers)

 

[Julf]

Certainly:
Purifi Audio - A Straight Wire to the Soul of Music
This Thing We Have About Hysteresis Distortion
Combating Hysteresis Distortion (part 1: Amplifiers)

I could not find any objective evidence that the difference is audible in that piece.

 

[Feyire]

I could not find any objective evidence that the difference is audible in that piece.

Let's start with background context from the first article (Purifi Audio - A Straight Wire to the Soul of Music).

This discusses a technical presentation that Bruno Putzeys (designer of NCORE and Purifi) gave at The Netherlands Audio Engineering Society (AES) section. The presentation discusses his new Purifi design and provides some history on an investigation into hysteresis distortion. This investigation was prompted by owners of NCORE modules complaining about a clearly audible "granularity" in the sound, which is something I have also heard from my own NC400s. Bruno's conclusion from that investigation was that the "ferromagnetic material of the amplifier output filter coil" was the culprit for this audibly reported issue.

The second article (This Thing We Have About Hysteresis Distortion) goes into the technical details of hysteresis and outlines measurements for showing the effect of it. The conclusion from the article regarding hysteresis is quite interesting to say the least:

Hysteresis distortion isn’t something that we simply decided to big up in search of a USP. It’s very real, very different from what you’d expect and not at all subtle. It takes the form of popping or crackling noises that go off at almost but not entirely random moments. You can’t rely on masking to render it inaudible because cause and effect are not coupled in time and the distortion level tracks the signal level. It is not like normal distortion that the ear just files away as colouration, or can otherwise get used to. Left to its own, hysteresis produces a recognisable grainy texture in the sound, a blanket of fuzz that always stays just this side of audible, taunting and infuriating like an itch you can’t scratch.

This is why we put so much effort into removing it from our amplifiers and speaker drivers.

So yeah, that's Bruno himself telling you that hysteresis is real, very much audible and very nasty.

In the third article (Combating Hysteresis Distortion (part 1: Amplifiers), Bruno outlines how he uses an updated feedback loop in the Purifi design to counteract the hysteresis distortion.

The conclusion I derive from the articles is that UcD and NCORE are sonically flawed, because the physical implementations employ iron core inductors in their LC filters and as such, suffer from audible hysteresis distortion. For any audio enthusiast, any audible flaw is obviously undesirable/unacceptable.

 

[Julf]

So yeah, that's Bruno himself telling you that hysteresis is real, very much audible and very nasty.

Seems we have different definitions of "objective evidence". I think the right description of what you are presenting is "appeal to authority".

 

[Feyire]

Seems we have different definitions of "objective evidence". I think the right description of what you are presenting is "appeal to authority".

As I stated, the second article (This Thing We Have About Hysteresis Distortion) goes into the technical details of hysteresis and outlines measurements for showing the effect of it. Is that not objective evidence for you?

Do you disagree with Bruno's research and conclusion regarding hysteresis distortion? If so, I look forward to you presenting your counter argument and appropriate objective evidence to the contrary.

 

[Julf]

As I stated, the second article (This Thing We Have About Hysteresis Distortion) goes into the technical details of hysteresis and outlines measurements for showing the effect of it. Is that not objective evidence for you?

Do you disagree with Bruno's research and conclusion regarding hysteresis distortion? If so, I look forward to you presenting your counter argument and appropriate objective evidence to the contrary.

I totally agree that hysteresis distortion can make a measurable difference. I am questioning the audibility of it. We can measure much smaller differences than what we can hear.

 

[Feyire]

I totally agree that hysteresis distortion can make a measurable difference. I am questioning the audibility of it. We can measure much smaller differences than what we can hear.

It is somewhat ironic I suppose, that it was people complaining of an audible anomaly (i.e. subjective reports), that led to hysteresis suddenly becoming such a discussed topic, and that the research and objective evidence only followed up much later to definitively confirm it as the source of the problem.

 

[sigbergaudio]

Let's start with background context from the first article (Purifi Audio - A Straight Wire to the Soul of Music).

This discusses a technical presentation that Bruno Putzeys (designer of NCORE and Purifi) gave at The Netherlands Audio Engineering Society (AES) section. The presentation discusses his new Purifi design and provides some history on an investigation into hysteresis distortion. This investigation was prompted by owners of NCORE modules complaining about a clearly audible "granularity" in the sound, which is something I have also heard from my own NC400s. Bruno's conclusion from that investigation was that the "ferromagnetic material of the amplifier output filter coil" was the culprit for this audibly reported issue.

The second article (This Thing We Have About Hysteresis Distortion) goes into the technical details of hysteresis and outlines measurements for showing the effect of it. The conclusion from the article regarding hysteresis is quite interesting to say the least:

So yeah, that's Bruno himself telling you that hysteresis is real, very much audible and very nasty.
.

"very much audible" and "nasty" is not a very accurate representation of this problem. In general nCore sounds great, and no one comparing either of these three amplifier modules blind would be able to say "oh, there's the nasty one" when listening to the ncore. On the contrary, they will not be able to discern any meaningful difference between any of these three (they are all very good) given a load that is acceptable to all modules.