Review and Measurements of Hypex NC400 DIY Amp

[restorer-john]

Another contender:

Denon POA-1500. 1983-1986. 35 years old. Got one here and a review someplace where it tested considerably better than spec.

Both channels driven at 8ohms, rated 150+150W @ 0.005% (20Hz-20KHz), 240+240@4ohms (20Hz-20KHz). THD at rated outpur <0.002%.

123dB S/N ratio and wait for it, 400V/uS slew rate. FR 1Hz-300,000Hz +0/-3dB.

Oh, and you don't get a bonus radio station's worth of RF spuriae to filter out.

 

[6speed]

Hypex do specify cont power for the OEM nCores eg NC500. Comparing the NC500 figures with the NC400 makes me think the NC400 actually is a ~80W cont power amp ... or?

The NC400 data sheet states that EN60065 only calls for a continuous power capability of 1/8th of rated output, and compressed pop will require 1/3 rated output. Having that thought be part of the design process makes sense when comparing the large difference between the continuous rating and the peak levels. Basically, it is thermally limited to 100W into a resistive load for an infinite amount of time, but for normal music, it will put out a lot of power.

That is also a different power supply with twice the output. Here is what we would want to verify with my amp with only a single channel driven. I halved my power supply to save space and money because I did not need the power.

 

[6speed]

The wiring for 1 smps600 for dual nc400, did you do it yourself?

Yes, I cut and spliced all the cables to make them as short as possible while still avoiding sources of interference. Hypex does sell a convenient connector for people to use a pair of NC400s with an SMPS700A400 to maximize power output. That would let you use their power cables without any modifications.

 

[restorer-john]

Having that thought be part of the design process makes sense when comparing the large difference between the continuous rating and the peak levels.

No, it's just typical BS marketing that is the default position these days. I for one, have no time for it.

The FTC had to put their foot down in 1974 to fix the mess that was amplifier specifications and in the decades since, manufacturers have pushed and pushed to get easier requirements, in order to have bigger headline numbers and little substance to back them up.

The 'dynamic nature of music' has been used for decades to justify shitbag construction, poor PSU regulation, inadequate heatsinking and as few output devices as they could get away with. I have many examples of amplifiers with phenomenal short term power, but that's all they are, turbo charged pocket rockets. NAD/Proton etc. Marantz with their AVSS. Pioneer with their commutating rail amps. They all give real headroom, but it was all done to advertise big numbers at a low cost.

Having built and repaired many hundreds of amplifiers, there is no substitute for a real power supply made of copper and steel. Big PSUs can take abuse that no SMPS can handle. The filter caps last forever at 50/60Hz. SMPSs fail so often in my experience they are a joke. You simply cannot pull current out of capacitors at the rates they do without the electrolyte heating significantly with the resultant venting failures. The life of SMPS filter caps is very short, regardless of their spec and nine times out of ten they are the cause of all problems in anything SMPS powered.

 

[6speed]

@restorer-john I understand enough of the games and degrees of cheating different manufacturers employ in order to inflate their numbers, and I am not trying to justify it, I just meant that their explanation was in agreement with the low continuous power rating. Fortunately, I only need 50 high quality Watts, and I knew how to read their data sheets and app notes prior to beginning the journey. I got what I needed without feeling cheated.

 

[March Audio]

No, it's just typical BS marketing that is the default position these days. I for one, have no time for it.

The FTC had to put their foot down in 1974 to fix the mess that was amplifier specifications and in the decades since, manufacturers have pushed and pushed to get easier requirements, in order to have bigger headline numbers and little substance to back them up.

The 'dynamic nature of music' has been used for decades to justify shitbag construction, poor PSU regulation, inadequate heatsinking and as few output devices as they could get away with. I have many examples of amplifiers with phenomenal short term power, but that's all they are, turbo charged pocket rockets. NAD/Proton etc. Marantz with their AVSS. Pioneer with their commutating rail amps. They all give real headroom, but it was all done to advertise big numbers at a low cost.

Having built and repaired many hundreds of amplifiers, there is no substitute for a real power supply made of copper and steel. Big PSUs can take abuse that no SMPS can handle. The filter caps last forever at 50/60Hz. SMPSs fail so often in my experience they are a joke. You simply cannot pull current out of capacitors at the rates they do without the electrolyte heating significantly with the resultant venting failures. The life of SMPS filter caps is very short, regardless of their spec and nine times out of ten they are the cause of all problems in anything SMPS powered.

As we discussed in the other thread its a very pertinent point. The average RMS level is significantly lower for music. The FTC test is interesting from a technical POV, but it bears no resemblance at all to real world usage.

Agreed on the issue of manufacturers playing games to inflate numbers, and a need to have a standard for comparison, but a more representative comparison criteria should be used.

 

[confucius_zero]

Can the SU8 preamp two of these NC400 amps?

 

[March Audio]

This ..

View attachment 19481

If those voltage numbers on the scale are correct that is a pretty low signal. about 9mv rms, so into 8 ohms thats about 10 mW. That will get your average 86dB/2.83V (nom 1 watt into 8 ohms) speaker to .....hang on need to do some calcs.......about 65dB ? The noise is obviously much lower again.

It would be interesting to see the spectrum of that noise though, as the AP input filter is 40kHz upwards, and what falls back into the sub 20 kHz region. Im guessing not much because you would not get this low noise floor otherwise ( acknowledging FFT process gain ):

 

[March Audio]

Can the SU8 preamp two of these NC400 amps?

When you say two, you mean a stereo pair? If so, yes.

 

[confucius_zero]

When you say two, you mean a stereo pair? If so, yes.

I guess what's left would be to daydream about an integrated that has both the SU8 DAC/Preamp + the NC400 amplification modules in a box no loss in the high measurement scores of both. That would be quite a monster, but scientifically possible?

 

[March Audio]

There may well be integrated products featuring Hypex technology already. I would have to check though.

 

[confucius_zero]

I would be interesting to see how Hypex compares to ICEPOWER technology.

 

[March Audio]

I would be interesting to see how Hypex compares to ICEPOWER technology.

Yes, I would like to see that.

 

[amirm]

Enough to establish a trend or see where it diverges. I would say 1W, 10W, 100W, full power.

I can only vary the input level so the output is whatever it falls at. Here are the results:

The graphs are not in order of input level. They fall on the graph based on noise level for the most part so I tried to label some and add the interpretation.

Perceptually our hearing is most sensitive between 1 and 3 kHz so it is nice to see distortion not falling in that region until way into power band.

 

[amirm]

Can you show some intermodulation distortion measurement?

Sure. Here you go:

The graph is against level versus power which makes it Apples vs Oranges in comparing to other amps but that is the template I had handy. Need to make one for power.

Just to help, at 1 volt input you have 63 watts of output power, both channels driven into 4 ohm. At max of 1.5 volt on the right, it outputs about 142 watts.

 

[Sal1950]

I can't even describe how much that makes me want to see a pair of monoblocks get tested

Very nice build, thanks for sending it in for review! We all benefit from these actions.

 

[amirm]

It would be interesting to see the spectrum of that noise though, as the AP input filter is 40kHz upwards,

The AP filter I use is actually nearly flat to 100 kHz. The spec calls for flat line to 40 kHz and hence that notion but it still pretty much allows a lot to go through well above that. Here is its response:

 

[restorer-john]

I can only vary the input level so the output is whatever it falls at.

That makes no sense. You always vary the input level in mV to obtain whatever nominal output voltage you want for a given wattage over a specific load with 1KHz as the reference point.

Well, that's what I do. I confirm gain in dB and sensitivity for rated power that way.

So we have 0.09% THD at 20KHz at 157W@4ohms? Bit disappointing wouldn't you say?

 

[March Audio]

The AP filter I use is actually nearly flat to 100 kHz. The spec calls for flat line to 40 kHz and hence that notion but it still pretty much allows a lot to go through well above that. Here is its response:

So looking at a time waveform (guessing 96kHz bw?) you might see some of the high frequency noise that isnt apparent in the sub 20kHz audible band?

Can you do an FFT of 20kHz to 96kHz to see if there is any garbage?

 

[amirm]

That makes no sense. You always vary the input level in mV to obtain whatever nominal output voltage you want for a given wattage over a specific load with 1KHz as the reference point.

What???

There are two nested sweep functions in this test: one for frequency and the other for generator level. The Analyzer can't control the output. It can graph the output voltage and hence show that in wattage but for some odd reason, you have to go into a completely different mode of the AP analyzer to get that capability. Hence the reason I said I have to create another template for it.