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Review and Measurements of Hypex NC400 DIY Amp

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how about measuring power consumption from the wall? Simply reporting Kill-a-watt numbers at idle, ~10W & full power would work for me. And I don't recall seeing such information from other sources.
If you want to take the manufacturer's word for it, they have a thermal design spreadsheet available here that will let model power loss based on system efficiency. Just add in power output and you have your total figure.

If you do use a Killawatt, someone once conducted a good test (maybe at a PC oriented site) that showed it could not measure power with any accuracy until >50W or so. I seem to recall at 10W it was sometimes off by 100%. That having been said, here are the results of some of my own tests with a Killawatt. Note, my published column is from the datasheets--I have not corroborated it with the spreadsheet.

Capture.JPG
 

HammerSandwich

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If you want to take the manufacturer's word for it...
Actually, I thought that it could be a useful addition to ASR's testing, to verify & supplement OEM specs. Not all the companies include this info, and ASR wouldn't bother testing if the specs were always trustworthy.

If you do use a Killawatt, someone once conducted a good test (maybe at a PC oriented site) that showed it could not measure power with any accuracy until >50W or so. I seem to recall at 10W it was sometimes off by 100%.
Good reminder. Should be easy enough to bias with a power strip & light bulb(s).

Thanks for your data. The PFs suprised me!
 

DonH56

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PFs are pretty low...
 

trl

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Not everyone agrees a "perfect" square wave is important. It is possible that the circuity added to make a "perfect" square wave actually hurts sound quality such as transient response. Here is a link to an article that recommends bandwidth limited square waves for amp testing and gives some illustrations on how to interpret them http://sound.whsites.net/articles/squarewave.htm
Depends what everyone's looking for, the below graphs show roll-off to trebles and to bass too, things that can get adjusted via the LowPass & HighPass filters from inside the amplifier. Blue-line is signal generator, red-line is amplifier's output:


100 KHz sinewave with the orginal LPF


100 KHz sinewave with modified LPF



20 KHz squarewave with original LPF


20 KHz squarewave with modified LPF



20 Hz squarewave with original HPF


20 Hz squarewave with modified HPF

I don't intend to pollute this measurements thread anymore, but I want it to add the above graphs for those that didn't read the Tektronics PDF file attached one page back. Thanks!
 

DonH56

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My tests historically used a LF square wave to assess LF performance (limited LF bandwidth would cause tilting) and look for any signs of LF oscillations like motorboating. I used HF'ish square waves to assess HF stability, looking for ringing and such, but would normally band limit them to 20 kHz ~ 100 kHz depending on the amplifier. Bear in mind that phono cartridges can generate signals well above 20 kHz and I had that in mind way back then when I looked for HF stability.
 

Shadders

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View attachment 19466

Performance actually improves up to about 30 to 50 watts and then starts to climb some. At near full clipping, we get healthy amount of power (225 watts both channels driven) with 0.004% distortion. It completely blows out of water the previously tested amps in both power and distortion/noise.
Hi,
If possible, could you produce plots for 20kHz THD+N versus Power Level output ?.

Many measurements i see for solid state class A/B amplifiers are with a measurement bandwidth of 80kHz. So, from a performance comparison, it is difficult to determine where a specific design excels or not.

If possible, can the same 1kHz THD+N vs Power Level output be overlaid to see the differences ?

Thanks and regards,
Shadders.
 

trl

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Very "chronofage" activity, with your plots and my squares Amir will definitely need couple of more apprentices in his "team". :)

I think guys from Audioholics does the Power vs. THD+N or at least max. power for 0.1% and 1% THD+N @ 20Hz, 1KHz and 20KHz. Also, max. output power and voltage might count and/or dBu, so anyone will be aware how many dB loss has the DUT lost @20Hz vs. @1KHz. Like I said...very time consuming indeed.
 
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rajapruk

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OK, here are the results of thermal stress test.

I hooked up input to one channel and let it the unit warm up driving that one channel at 40 watts. I logged THD+N during that time and got this:

View attachment 19779

There is some equilibrium that occurs after 3 to 5 minutes but then thermal effects start to set in and distortion increases a bit (1 dB or so). An arrow to the heart of people who think they should leave the gear on 24/7. :D

I then jacked up the power to 330 watts or so and started to cook the unit. Here is the above graph again:

View attachment 19782

Here is the power measurement showing the shut down with power dropping to zero:

View attachment 19783

I had hooked up a 4-channel themorcouple and here are the results at the end of warm-up (left) and max power (right):

View attachment 19784

As you see, the large power supply heatsink was the hottest at 81 degrees. Strangely, shortly after I took the above right picture, two of the thermal probe started to glow red in the middle and completely melted the insulation!!! Cheap junk. :)

Thermal imaging showed I had probed the wrong things:

View attachment 19785

As noted, the hottest components were actually the inductors/transformers! Both in the amp and power supply. Max temp for the large power supply transformer is about 101 degrees C. Wonder what their wire insulations are rated at.

After the stress test, I ran a power versus distortion test:
View attachment 19786

Power increased to 315 watts which is not much more than when both channels were driven. Distortion performance is the same as when the unit was much cooler in the original review.

Now please me go and cry over my damaged thermocouple meter.....
Do you think adding additional heatsinks on top of the existing heatsinks would prolong the life of this SMPS?
 
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I think the best things you can do to prolong the life of the amp as a whole are in descending order of effectiveness or attraction (to me):
  1. Limit current by only using the amp within a fraction of its rated output. This will naturally be the case for most people, and is probably what Hypex was banking on. I need about 5W for TV and 50W for very loud music.
  2. Use the SMPS1200 instead since it has far better heatsinking.
  3. Operate in dual mono mode instead of stereo (two SMPS600).
  4. Use a better vented chassis.
  5. Use forced air cooling. This could be very effective, but no one wants to do it.
 

RayDunzl

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Use forced air cooling. This could be very effective, but no one wants to do it.
I do!

I have three 3-speed computer fans connected to an old PC power supply, all on low, all quiet enough, one on each amp heat sink, one blowing across the top of the preamp, just to provide a little flow...

They're silent (to me) as soon as anything else starts happening at all.
 

Ron Texas

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@amirm what voltage level does it take to drive this Hypex amp to full power? I have noticed a lack of a published specification in this area.

These relatively inexpensive Hypex amps all have 26 db voltage gain: https://www.nordacoustics.co.uk/nord-one-hypex-ncore-mpxxx-stereo-p
I attempted to calculate input sensitivity for the 200 watt @ 8 ohms model and came up with 2.15v. It would be higher for the 350 watt @ 8 ohms model. That means perhaps a preamp is optional on the first, but required for the second.

Can you or any of the engineering wizards around here comment on this?
 

amirm

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Do you think adding additional heatsinks on top of the existing heatsinks would prolong the life of this SMPS?
It should but a less invasive approach may be to put a fan in there and have it only come on in extreme cases.
 

amirm

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@amirm what voltage level does it take to drive this Hypex amp to full power? I have noticed a lack of a published specification in this area.
I don't remember anymore. But here are the sweep parameters for the power graph:

1547233329915.png


As you see I had to go up to 2 volt to get past clipping point.

The 5 minute run was at 1.9 volt input to generate 335 watts at 4 ohms.
 

Ron Texas

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I don't remember anymore. But here are the sweep parameters for the power graph:

View attachment 20229

As you see I had to go up to 2 volt to get past clipping point.

The 5 minute run was at 1.9 volt input to generate 335 watts at 4 ohms.
Thank you. I suppose that is preamp optional with a lot of DAC's as many top out at 2V output.
 

RayDunzl

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Can you or any of the engineering wizards around here comment on this?
Your number looks reasonable.

Krell Amp Manual, three models in the series, 26.4dB gain for each:

1547234270398.png


Matching preamp:

1547234380896.png
 
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My almost 100% silent PC is in a cabinet, which does make it silent, and I have a pair of 200mm Noctua fans venting the cabinet. I have a cheapo voltage regulator dialing a power supply down to provide enough airflow without generating any noise. I had thought about doing something similar for several shelves in my stereo rack...
 

garbulky

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Just want to note that we don't know if we need to "prolong the life of the amp". There's no indication that there is a real life problem.
 
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