Review and Measurements of Hypex NC400 DIY Amp

[March Audio]

As Amir pointed out, it's a 40KHz and 60KHz spur that is causing that number.

So my question would be, is 20kHz a reasonable frequency to asses THD at considering those harmonics are inaudible and un-reproducible by pretty much any speaker?

 

[restorer-john]

If you are willing I will pay for you to send it over here as it sounds like a good reference..

It's 20kg net. And it has a matching mint condition preamp, so sending it to WA is a death sentence.

I do have a not-so-mint one in the storeroom I could dig out and possibly do that. Pity you aren't closer, we'd have field day with big power amp testing.

 

[restorer-john]

Just looked at the distance... An 8686km round trip to Perth via shortest distance roads. My poor amplifier would never be the same.

I'll send you a picture instead.

I guess if I got off my backside and got a front end A/D-D/A like yours and Virtins, I could do it myself.

 

[Olli]

We may have a contender...

View attachment 19500

https://www.stereophile.com/content/benchmark-media-systems-ahb2-power-amplifier-measurements

*I misread the chart caption, the above was the 4 ohm measurement.

Great review, thanks Amir! Since the audible difference of (top tier) DACs is somewhat limited at least to me, I am really looking forward to more amp reviews. Especially the Benchmark AHB2 (I have ordered a pair of AHB2s and a DAC3 B that hopefully arrive next week) - is this one on your list to get reviewed anytime soon?

 

[andreasmaaan]

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%.

View attachment 19484

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.

Great measurement.

Do you know of any amp John that has as low distortion as this Hypex does when running as a monoblock?

 

[rajapruk]

Built these nCore NC400 monoblocks five years ago. Notice the heatsinks, really good chassies from a German firm, name escapes me now.

View attachment 19479

They never made it for me, could it be the jagged waveform, sold them after a year or so.

Would be interesting to see how much they can deliver continously (FTC way), seems as they only publish Peak power for the NC400.

View attachment 19480

My subjective opinion when I had nc400 was that they were not perfect in the treble region. But damn perfect in bass region. Subjectively.
Maybe this is confirmed now then here with the rising distortion in higher frequencies?

Amir, will you do subjective listening test?

 

[andreasmaaan]

Maybe this is confirmed now then here with the rising distortion in higher frequencies?

Where do you see that in the measurements?

 

[amirm]

Presumably in the dashboard in the OP at 5watts this was obscured in the noise floor because of minimal averaging/lower FFT resolution?

Yes. The dashboard uses 32K FFT and this one, 256K.

 

[amirm]

My example was one I put up as it had a low THD, high power and tested very well back in the day and I have a few of them here I could run some tests on. Trouble is, confirming those numbers is a real challenge for me with my gear.

I looked up the Denon and it goes for $690 plus $100 or so in shipping so quite pricey for an experiment like this. If you can nominate something cheaper I could try to buy one and measure.

 

[amirm]

Great review, thanks Amir! Since the audible difference of (top tier) DACs is somewhat limited at least to me, I am really looking forward to more amp reviews. Especially the Benchmark AHB2 (I have ordered a pair of AHB2s and a DAC3 B that hopefully arrive next week) - is this one on your list to get reviewed anytime soon?

Thanks. I have not asked for the Benchmark. I do have the relationship with them now so in theory it is possible. Let me grind through the amps I already have so that we know where we stand when we get the Benchmark. This thread has already fleshed out a lot of tests we need to run so we will be in better shape testing the AHB2 in a few weeks.

 

[Krunok]

I don't know. I just shut off the input to one channel so it was powered on but not getting signal.

It would be interesting to unplug one of the amp modules and repeat some of the tests to see how this would perform as mono block. It may as well be that power supply is limiting the performance when driving 2 amps.

 

[restorer-john]

Do you know of any amp John that has as low distortion as this Hypex does when running as a monoblock?

Take the Sony TAN77es (or the TAN-80es). I have two of them here, they can run in monoblock operation putting out 580W+ each @8 ohms and over 850Watts at 4ohms. Their distortion is even lower at all powers.

I have some reviews, but they are thin on the technical measurements. I could only confirm power in stereo mode, the mono BTL operation is well beyond my current dummy loads, even when series/paralleled. Distortion is below what I can reliably measure.

As for frequency response, there is no comparison.

Our friend Ken Rockwell performed a comprehensive review here:

https://kenrockwell.com/audio/sony/ta-n77es.htm

Note, he refers to my information on the multivoltage units vs the US model (having a overly active protection system) I discovered back in the early 1990s and provided details to Axel when he was still running the Vintage Knob. (scroll down to the green text) http://www.thevintageknob.org/sony-TA-N77ES.html

Before dismissing KR, note his audio reviews are extremely well done IMO, although filled with his usual absolutes when it comes to opinions.

 

[Krunok]

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

Not at all. THD figure at 20kHz is pretty much irrelevant as it can't possibly be heard.

 

[restorer-john]

Not at all. THD figure at 20kHz is pretty much irrelevant as it can't possibly be heard.

Oh come on. This is getting ridiculous. We have been blessed with strict testing regimes to quantify and qualify high fidelity equipment for many, many decades. There are industry pioneers who would be collectively turning in their graves to hear that THD at 20KHz is irrelevant as it can't be heard.

What about THD below 0.1%? Apparently that can't be heard either, so it's also irrelevant? Hey, why bother with an APX-555 if an iPhone app can measure THD? This is either audio-science review or 'let's dismiss decades of engineering and science because we're not sure you can hear it or not'.

And the same people who say this are also extolling the virtues of high sampling rate, high 'res' music?

Give me a break.

 

[March Audio]

@amirm can I just confirm something, your graph in #52 is THD +Noise yes? If so we have all been a bit dim because we are comparing the Denons THD to THD +N Doh!

This is from the datasheet for info. @ 6kHz 150w THD+N is about 0.0009% and 1kHz its about 0.0007%, slightly lower than the Denon @ about 0.00085%


Plus the Hypex data is for 4 ohms and Denon for 8 ohms. Higher current for the hypex (6 amps v 4 amps). I wont speculate if it would be better into 8 ohms or if the Hypex data is entirely accurate. Obviously used an AP though.

 

[amirm]

Unless I say otherwise, I always measure THD+N. I also suspect the Denon measurements were the same.

 

[March Audio]

appears to be just THD

 

[amirm]

It would not have such high levels at low amplitude if it were just THD. Analyzers of the time would not have had the capability to measure just THD. It was common (and still is) to truncate THD+N to just THD.

 

[March Audio]

It would not have such high levels at low amplitude if it were just THD. Analyzers of the time would not have had the capability to measure just THD. It was common (and still is) to truncate THD+N to just THD.

?

 

[restorer-john]

Analyzers of the time would not have had the capability to measure just THD.

This is perfectly true. My standalone old THD analog meter is really THD+N as the 'N' component was traditionally below the THD and the total harmonics dominated the residual.

All we had was THD and residual noise. THD was the dominant number until the 80s when it swung the other way. Digital is to blame. Then along came the AP system 1...