Hypex NCx500 Class D Amplifier Review

[Rob Fens]

As I posted, from Amir's measurements, the monoblock amp is capable of 700W at 2ohms. Since my speakers have a 2 ohm impedance, yes, I am ok with that. Yes, the modules would come closer to their potential with a beefier smps, which is what I have been saying over and over.

I guess nobody disagrees about the influence of the psu, it is a fact that a smaller psu will cause the amp to deliver less power. Even laymen will understand, if somebody does not get enough food, this person will (under)perform accordingly. But i guess it is only about the word "bad". Since everything is transparent, the discussed phenomenon should be expected and will not be a surprise for the well informed, and people on this forum are very well informed. So an amp with a too small psu will not stop the system working. The only "BAD" thing which happens is that the maximum SPL will be a few db less. I think that nobody can hear he difference between 106 or 110 db. I agree, if you want the higher SPL, it is a disappointment, but calling it bad, you would not even notice.

 

[Sokel]

Here is THD vs Power measure of a NCx500 monoblock amp (identical to review unit) using my new test setup (E1DA Cosmos ADC with high power dummy load)...
View attachment 295017

While have not been able to get noise down to Amir's levels, the power curve is very comparable with clipping at 420 watts and 1% distortion around 660 watts.

Pretty good given that it did not cost anywhere close to what Amir spent on his AP!

THD or THD+N?

 

[RickS]

THD or THD+N?

THD. As I mentioned, have not gotten noise fully tamed as yet…

In loopback, get to about 4 uV. With input shorted, measures in tens of uV. With all wiring and filter is over 100 uV. As shorting input gives me a good relative read, is good enough to know whether there is major issue or not.

 

[mdsimon2]

THD. As I mentioned, have not gotten noise fully tamed as yet…

In loopback, get to about 4 uV. With input shorted, measures in tens of uV. With all wiring and filter is over 100 uV. As shorting input gives me a good relative read, is good enough to know whether there is major issue or not.

When you say 4 uV in loopback is that DAC to ADC? If so that DAC will probably limit from a noise perspective when making amplifier measurements at lower power levels, especially when using the buffer. What DAC are you using?

Michael

 

[RickS]

W

When you say 4 uV in loopback is that DAC to ADC? If so that DAC will probably limit from a noise perspective when making amplifier measurements at lower power levels, especially when using the buffer. What DAC are you using?

Michael

Yes, DAC is Topping E50 and noise level was very close to Amir’s measurement of it.

 

[mdsimon2]

W


Yes, DAC is Topping E50.

I thought it would have been a bit better (I get 3.5 uV on my Okto which is higher noise than the E50) but it will depend on the Cosmos input setting.

Amplifier power sweeps are challenging as ideally you have an autoranger to keep the ADC near 0 dBFS and you have similar automatic analog attenuation on the DAC side. You can make good one-off measurements (say at 5 W in to 4 ohm to match ASR) by setting the ADC input level appropriately and using a voltage divider on the DAC output.

Michael

 

[RickS]

I thought it would have been a bit better (I get 3.5 uV on my Okto which is higher noise than the E50) but it will depend on the Cosmos input setting.

Amplifier power sweeps are challenging as ideally you have an autoranger to keep the ADC near 0 dBFS and you have similar automatic analog attenuation on the DAC side. You can make good one-off measurements (say at 5 W in to 4 ohm to match ASR) by setting the ADC input level appropriately and using a voltage divider on the DAC output.

Michael

The power curve is so close to Amir’s, may just be dealing with DMM accuracy or dummy resistor tolerances. If I round up the RTA cal a bit, pretty sure inflection points would match his.

 

[Heuboda]

Thank you Amir for all the effort and tests you do for us. Because the tests for the Hypex NCX500 and the Topping A70 and D70 has been so good, I was buying them and I am not disappointed regarding sound quality and power. Even my loudspeaker with an impedance of 0,6 Ohm handled the Hypex modules very well.

 

[Matias]

@Heuboda welcome to ASR. That is one minimalist and beautiful system, congrats!

 

[Sokel]

Even my loudspeaker with an impedance of 0,6 Ohm handled the Hypex modules very well.

Which speaker is this?

 

[Heuboda]

Which speaker is this?

Martin Logan Renaissance 15A. I think the impedance at 20kHz is even 0,4 Ohms. I have to double check.

 

[RickS]

To my point about the 700 watt rating of the NCx500, we know this is at 1%THD with a 4 ohm load. While we may argue audibility at this level, I had pointed out earlier that the amp was clipping at that point. Something always bothered me about being "comfortable" with the rating, but could argue that it is useful for comparison purposes. Now with REW as my measurement software, there is an oscilloscope feature, so thought I would try it out. The test tone is at 1 kHz and here is how it looks just shy of the rated output...

As you can see the tops and bottoms of the sine wave are clipped (slightly). So, while the NCx500 hits its rating, it is hardly ideal. Imo, would seem more appropriate to comfortably call it a 400 watt amp (at 4 ohms and really low distortion.) Amir's measurements appear to mostly support that level. If you are good with that, well what about a more complex load? For now will leave that to others. Here is a look at my 4 ohm power curves...

 

[Matias]

But wouldn't other amps show similar clipped sine waves at 1% THD?

 

[goryu]

Then you can call the Purifi a 250W amp. Or whatever else you want. I will compare using legitimate manufacturer's nominal ratings. What's relevant for my use are the outputs relative to other amps.

 

[antcollinet]

But wouldn't other amps show similar clipped sine waves at 1% THD?

Exactlly - see the waveforms here:

c200 THD and Full Power Testing @ AmpsLab

Before we proceed with power testing, substitute the dummy load with a 200 watts, 8 ohms resistor.

ampslab.com

 

[RickS]

But wouldn't other amps show similar clipped sine waves at 1% THD?

Yes, was just illustrating what it looked like as have not had any oscilloscope capability previously. Thought it might be useful for some members too!

p.s. should add clipping is one form of waveform distortion. you could have a waveform distortion without a visibly clipped waveform.

 

[RickS]

Btw, for more comprehensive discussion of distortion, see @DonH56‘s useful thread here:

Harmonic and Intermodulation Distortion

This post provides a quick comparison of how a distortion percentage relates to dynamic range in dB. That is, if an amplifier has 1% distortion, what does that mean? How soft (or loud) is 1%? Figure 1 shows a 1 kHz voltage signal with 1% second harmonic distortion (HD2) added. The spectral...

www.audiosciencereview.com

I was not aware of this content previously, but visually shows examples of different cases. Thanks Don!

 

[pawsman]

Btw, for more comprehensive discussion of distortion, see @DonH56‘s useful thread here:

Harmonic and Intermodulation Distortion

This post provides a quick comparison of how a distortion percentage relates to dynamic range in dB. That is, if an amplifier has 1% distortion, what does that mean? How soft (or loud) is 1%? Figure 1 shows a 1 kHz voltage signal with 1% second harmonic distortion (HD2) added. The spectral...

www.audiosciencereview.com

I was not aware of this content previously, but visually shows examples of different cases. Thanks Don!

Rick,
What's your opinion of the IceEdge1200as Module compared to the new Hypex NCx500? I've got the 1200as from Mivera Audio in a cheap case; I've been
happy with it; it has plenty of power for my Legacy Calibre Monitors. BTW, are the specs for that amp valid (600/8 ohm ; 1200/4 ohms)? I don't see how that module can deliver the current for 1200 watts. Would it be worth trading up? Thanks-

pawsman

 

[Sokel]

Rick,
What's your opinion of the IceEdge1200as Module compared to the new Hypex NCx500? I've got the 1200as from Mivera Audio in a cheap case; I've been
happy with it; it has plenty of power for my Legacy Calibre Monitors. BTW, are the specs for that amp valid (600/8 ohm ; 1200/4 ohms)? I don't see how that module can deliver the current for 1200 watts. Would it be worth trading up? Thanks-

pawsman

I also have it for lows,power is there as we saw from Amir's test of Peachtree (1200/4 Ohm refers to 1 channel driven for 90 sec if you read the data sheet).
Mind that Peachtree is not the bare module,it also has some "audiophile" buffer in front of it,probably adding noise:

Peachtree amp500 Amplifier Review

This is a review and detailed measurements of the Peachtree amp500 stereo amplifier. It is on kind loan from a member and costs US $1,499. The amp500 comes in the same packaging of many previous Peachtree products. I wish company would innovate here as the design looks kind of dated. Then again...

www.audiosciencereview.com

 

[RickS]

Rick,
What's your opinion of the IceEdge1200as Module compared to the new Hypex NCx500? I've got the 1200as from Mivera Audio in a cheap case; I've been
happy with it; it has plenty of power for my Legacy Calibre Monitors. BTW, are the specs for that amp valid (600/8 ohm ; 1200/4 ohms)? I don't see how that module can deliver the current for 1200 watts. Would it be worth trading up? Thanks-

pawsman

I have eyed the IceEdge amps but have plenty of Hypex and a Purifi amp. Reportedly they are a step down in terms of performance but liked the construction and protection features. Would not expect any diff in sound quality and seems like the 1200as has plenty of power. If you are happy, would not change. If you are curious, would take advantage of a trial period on Hypex or Purifi amp.