Review and Measurements of Nord One NC500 Amp

[dinglehoser]

Given that the seller is in UK, getting it repaired/replaced would be quite onerous. So I can't make that decision on my own.

Amir - go for it. If Hypex says they're rated for 100 continuous watts, I see no reason why running 100W continuously would cause any issues ... especially with such a large case as a heat sink. Would be interesting to see how it's distortion/noise/power profile changes as it warms up.

 

[McFly]

Amir - go for it. If Hypex says they're rated for 100 continuous watts, I see no reason why running 100W continuously would cause any issues ... especially with such a large case as a heat sink. Would be interesting to see how it's distortion/noise/power profile changes as it warms up.

Wooo, now we're cookin' with gas. Maybe i should send amir one of my NC400 monos (from the hypex site) for a cook off. Postage could be a bit...

 

[March Audio]

OK, put it this way. Do you think that an Audio Amplifier should reproduce or emit anything other than an amplified, un-distorted version of the original signal and absolutely nothing else?

Many Class Ds wipe out AM radio reception and render shortwave unlistenable. Many Class D chips offer variable carrier adj taps so when installed in or near a tuner board, the tuner board actually partially works.

Class D as a whole is attempting to control the message (unsuccessfully IMO) that spurious RF/EMI at high levels is not a problem, when previous to its implementation, any noise, any spurious tones, any un-correlated EMI/RFI was indicative of a faulty design.

Sorry John but with respect you are generalising. Obviously I havent tested the plethora of class D amps out there but Hypex amps simply do not emit large amounts of spurious RF.

Below is the RF spectrum of one of my P252 amps. The Hypex NC252MP board is sat on the desk, not in a case and connected by a couple of meters of speaker cable.

The antenna is 1 m away. The scope is measuring the switching frequency as 405 kHz.

You can very nicely see the AM radio stations, our local ABC Radio Perth being the strongest at 720kHz.

Amp off

Amp on

No 405kHz or harmonics of.

 

[March Audio]

And here we go again.

Hypex watts are essentially the New Millennium Versions of Peak Music Power watts of last century.

At least run it for 5 minutes at 100W (its 'real' rated power) as a bare minimum. If it blows up or shuts-down, it's a genuinely faulty design and should be exposed as such.

John, you have seen the videos of my Hypex amps passing the 5 minute FTC power rating test.

 

[amirm]

Amir - go for it. If Hypex says they're rated for 100 continuous watts, I see no reason why running 100W continuously would cause any issues ... especially with such a large case as a heat sink. Would be interesting to see how it's distortion/noise/power profile changes as it warms up.

OK, here it is:

Ignore the initial glitch which was me turning off the generator by accident. I say from thermal point of view, the Nord One passes with flying colors. The top of the enclosure did not change temps at all. Bottom of the unit below the amps was slightly warmer than room temp. It can output this level of power forever.

 

[McFly]

Maybe this is what "run-in" is. Increase in distortion.

 

[restorer-john]

John, you have seen the videos of my Hypex amps passing the 5 minute FTC power rating test.

Yes, I did. Your amplifiers have a CNC machined single piece of Al and I'd bet they'd out-do this Nord long term, even though they are smaller.

 

[JJB70]

Power rating became devalued by all the tricks used by manufacturers to artificially boost their brochure figures. If something is rated for a continuous rating of 100W then there should be no risk from running it at 100W.

 

[daftcombo]

What is the 12V trigger option?

 

[Matias]

Yes, I did. Your amplifiers have a CNC machined single piece of Al and I'd bet they'd out-do this Nord long term, even though they are smaller.

So you agree this is only a cooling matter, not some Hypex lie as you seem to imply.
Noone runs an amplifier at full power for several minutes outside lab testing. Musical signal has peaks, and that is why having a powerful module that can handle them is good.

If an amp would be running at full power all the time then the issue is only thermal dissipation. Say for example that a manufacturer adds huge heatsinks and even a fan or two. Now this amplifier would be designed for long term lab testing, great. But why would any manufacturer build them like that if 99.99% of its customers would not need all this, and would be paying and lifting these heatsinks for no use in music listening? This is where lab testing and real world must be understood and separated. The same goes for 450 kHz noise that is not even reproduced, let alone heard. Back to the real world, please.

 

[Matias]

What is the 12V trigger option?

Some sources or receivers have 12V trigger out, so that when one turns on the source it automatically turns on the amp for convenience.

 

[Samoyed]

Somewhere in a deep, remote forest, a tree fell....

 

[maty]

Mola-Mola mono amp, with Hypex NC1200

Picture optimized and rotated. From https://darko.audio/2015/08/kih-24-gone-fishin-for-perfection/

By the way, I can see.... a RFI/EMI IEC inlet filter. During my participation in the discussion about the first implementation of the ICEpower 1200AS2 module (bavmike, Mivera, in Audiocircle forums), I suggested its need.

I have a lot of RF/EMI Schaffner FN9244B in my two audio systems. And Würth 150 kHz ferrites.

* B: medical

 

[Xulonn]

Obviously I haven't tested the plethora of class D amps out there but Hypex amps simply do not emit large amounts of spurious RF.

I wonder if this (spurious RF causing interferance) is an issue that Hypex, ICEpower, Abletec and other Class-D amplifier module manufacturers have been actively working on? Do you know of any discussion of the issue in the audio engineering literature? Is there any available history of attempts to minimize it?

 

[maty]

With the first ICEpower 1200AS2 implentation I insisted repeatedly on two things:

* Cables with star-quad geometry. In and out (power cable too). He chose the very expensive and highly appreciated by audiophiles: Furutech 55.

* That aluminum is very bad to protect from the RF / EMI present in the atmosphere. Walls of at least 4 mm are needed. On the other hand, galvanized steel with 1 mm is sufficient. The second box, expressly manufactured, has sufficient aluminum thickness.

That thickness error is suffered by many devices, being especially serious in preamplifiers and DAC. Well, and phono.

 

[March Audio]

Interesting, Mola Mola Kaluga amp uses 2 wires per connector, in a star quad configuration. Now this is not done by both Nord and Apollon. Plus some fancy Furutech connectors and stylized case to justify charging $16,5k.

That's nc1200 module not Nc500. It has 2 sets of output connections on the plug. You can use this to make bi wiring easy or to reduce connection impedance. The module can kick out 40 amps!

 

[Samoyed]

Well, as casuistry is in vogue, I don’t like the color of some of the Moola Moola wiring and suggest it affects the sound....

 

[Samoyed]

QED.

 

[Ron Texas]

Given that the seller is in UK, getting it repaired/replaced would be quite onerous. So I can't make that decision on my own.

In an email someone from Nord said they did have a US repair facility (probably a contractor). Also, modules were user replaceable. Probably not the level of service your customers get, but not like Chi-fi.

 

[NielsMayer]

I wonder if this (spurious RF causing interferance) is an issue that Hypex, ICEpower, Abletec and other Class-D amplifier module manufacturers have been actively working on? Do you know of any discussion of the issue in the audio engineering literature? Is there any available history of attempts to minimize it?

Careful with using those ferrite beads.....

https://hal.archives-ouvertes.fr/hal-01103584/document

This paper showed that ferrite beads used for EMI suppression
in Class-D amplifier systems, have a non-negligible effect
on the amplifier audio quality. In the time domain, the ferrite bead nonlinear behavior is seen as peaks apparition at voltage
zero crossing. This can be translated to the frequency domain
by an increase of the odd harmonics in the audio frequency
band.
Furthermore, the THD measurements showed the impact
of the ferrite bead on the audio quality for all the tested
frequencies and a wide range of signal amplitudes. The
THD measurements and FFT calculations proved, therefore,
the significant impact of these non-linearities on the audio
performance.
This paper highlights the need of a model taking into account
the ferrite bead non-linear behavior, to help the designers
choose their optimal ferrite bead."

Ferrite bead effect on Class-D amplifier audio quality
"Kevin El Haddad, Roberto Mrad, Florent Morel, Gael Pillonnet, Christian Vollaire, et al.. Ferrite
bead effect on Class-D amplifier audio quality. IEEE Mediterranean Electrotechnical Conference,
Apr 2014, Beirut, Lebanon. IEEE Mediterranean Electrotechnical Conference, 2014, "

As can be seen from Fig. 9, the ferrite bead deteriorates
the signal THD in the amplitude range [10 mV - 7 V ]. Ferrite
beads have a negative impact on the audio signals even though
the component current in the range of [1 mA - 737 mA] is
lower than the component rated current which is 2 A. However,
below 10 mV the amplifier output noise does not allow any
comparison. Moreover, Fig. 10 shows that the ferrite bead
increases the THD on the entire frequency range. Note that,
beyond 6.5 kHz the THD measurements decrease suddenly.
This is because some of the odd harmonics are already out of
the audio band.
As a result, the ferrite bead increases the THD of the signal
delivered by the amplifier at all frequencies and a wide range
of signal levels. The deterioration caused by the ferrite bead
can reach −35 dB. Note that, −40 dB of THD level can be
distinguished by the human ear. Thus, the ferrite bead reduces
the audio quality of the amplifier due to its nonlinear effect in
the audio band