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Apollon NCx500ST Stereo Amplifier Review

Rate this amplifier:

  • 1. Poor (headless panther)

    Votes: 3 0.7%
  • 2. Not terrible (postman panther)

    Votes: 4 0.9%
  • 3. Fine (happy panther)

    Votes: 31 7.2%
  • 4. Great (golfing panther)

    Votes: 392 91.2%

  • Total voters
    430
When they specify 20-20000 Hz, they are clear that it covers the test frequency from 20 to 20,000 Hz. You are right, without also specifying the test bandwidth, they are not being clear about the bandwidth used for the measurements.
If that is the case, then @restorer-john these manufacturers published spec doesn't carry too much weight.

The moral of the story? Buy your own audio measuring equipment or send everything to Amir to test. My QuantAsylum is coming in sometimes this week, I had enough of these intentional ambiguity from manufacturers.
 
The NCx amp is still great with the test frequency up to 5 kHz. At the higher frequency, for class D amp I think you can expect it would not be as pretty because the output filters are not brick walls.
100% agree, even at the worse measured test frequency input, it's still less than .05%. But if that is the current technical limitations of Class D, then this gives a lot more reasons why Class AB is not antiquated and its not the technology of yesterday. AND. . .that Class A/B still is deserving of your desires today.

@amirm any reason why you stop the test frequency input at 15kHz? Why not go up to 20kHz?
 
This is all FAQ #7.

 
This is all FAQ #7.

Agree that it's inaudible, just like 100db SINAD is way beyond our human hearing threshold, yet. . .here we are, still measuring and buying based on these measurements. :facepalm:

I can't tell you why others do it, but I do it because I appreciate the engineering marvel, I have OCD and it gives me a peace of mind and let's me sleep better at night.
 
OK, I'll bite. Where does your 99% number come from? You and I both know the answer to that...

Peak or continuous power at 1kHz has always been a cop-out for amplifiers incapable of delivering their rated continuous power across the audible bandwidth. Because amplifiers back in the day (and plenty now) could not produce their rated power at frequency extremes. It's always been the "realm" (your word) of manufacturers who attempt to game the system with smoke and mirrors. It was one of the main reasons the Amplifier Rule was created and enforced in the first place!

We've been having this discussion long before you were screwing Hypex/Purifi modules into boxes and will continue to do so long after. Reputable manufacturers rate their amplifiers in accordance with FTC requirements for advertising power output specifications, which provide for continuous average (not peak) power across a defined bandwidth (usually 20Hz-20kHz), a specific load and with distortion not exceeding a specified amount at any power level from 250mW to continuous rated power. You do not do that.

The design of these amplifiers means they cannot sustain continuous rated power at high frequencies.

Let's pick 4 of the most reputable amplifier brands in the world shall we? Randomly chosen, currently available models.

McIntosh:
View attachment 311387

Accuphase:
View attachment 311388

Bryston:
View attachment 311389

Boulder:
View attachment 311390

And here is an NAD, using Purifi modules (they are smart enough to derate the amplifiers so they are compliant):
View attachment 311395
View attachment 311394Top


Your ratings for this review amplifier are as follows:

View attachment 311391


  • Your power rating does not specify a bandwidth for full rated power.
  • Your rated power output does not include a distortion number.
  • Your distortion figure is useless, as you don't specify a power output it is measured at. (we know it's just a best case, bottom of the curve number)
And
  • You make NO mention anywhere of the 1kHz frequency you are apparently rating your amplifiers at.
Dear @restorer-john

Per our recent discussions, I have conducted comprehensive tests with two NCx500 modules incorporated into our Apollon NCx500 DM dual mono amplifier. In order to rigorously assess their performance, I subjected the NCx500 to demanding conditions: running them continuously for 5 minutes at 20kHz over 500 watts into a resistive 4Ohm load (0.001 THD+N), and at 1kHz over 500 watts into a 4Ohm resistive load (0.1 THD+N).

I'm pleased to report that the amplifier performed exceptionally, maintaining 500 watts at 20kHz for the entire 5-minute duration. Interestingly, the NCx500 modules exhibited lower temperature increases at 20kHz compared to 1kHz. After the test, the NCx500 modules reached temperatures of 60 degrees Celsius (140 degrees Fahrenheit), while the Hypex SMPS 1200 power supplies and the enclosure maintained a consistent 30 degrees Celsius (86 degrees Fahrenheit).

To further align with FTC standards, the amplifier was preconditioned at one-eighth of its rated total power output for one hour using a 1,000 Hz sinusoidal wave.

Through this examination, I hope to conclusively demonstrate the robust capabilities of class D amplifier modules, particularly in response to skepticism about their performance at higher frequencies and continuous power. The modules in the test were housed in a 2.5mm thick enclosure. Given this, it's exciting to contemplate their potential performance in our more robust 10mm all around aluminum enclosures or within our premium amplifiers, which feature expansive heat sinks.

Reflecting upon the capabilities showcased, I am compelled to ask: who might require power beyond what this offers? This isn't merely a powerful amplifier; it stands as a testament to unparalleled power, delivering remarkable performance, especially when considering its compact form, weight, affordable price and efficiency.

For optimal clarity, kindly ensure that the video quality on YouTube is set to 1080p or 720p.



In light of your valuable feedback, I concur that our website should provide more detailed specifications showcasing the true prowess of our amplifiers. Not doing so would indeed undersell their capabilities. Rest assured, we will be updating this information shortly.

Thank you for your insightful suggestions and unwavering support.
 
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100% agree, even at the worse measured test frequency input, it's still less than .05%. But if that is the current technical limitations of Class D, then this gives a lot more reasons why Class AB is not antiquated and its not the technology of yesterday. AND. . .that Class A/B still is deserving of your desires today.

@amirm any reason why you stop the test frequency input at 15kHz? Why not go up to 20kHz?
My guess is that the AP AUX filters are not rated for precision measurements above 40 kHz. Amir reports his wide bandwidth THD+N to 45 kHz, which covers HD3 up to 15 kHz.
AP AUX Filters.png
 
Agree that it's inaudible, just like 100db SINAD is way beyond our human hearing threshold, yet. . .here we are, still measuring and buying based on these measurements. :facepalm:

I can't tell you why others do it, but I do it because I appreciate the engineering marvel, I have OCD and it gives me a peace of mind and let's me sleep better at night.
We can debate the merit of measuring up to less than 20,000 Hz, or even a little higher, but I don't think anyone would claim, or even suspect they can hear 30,000 Hz and above. So the time and effort to measure SINAD at 20 kHz or higher should better be spent on additonal test/measurements that are more useful, potentially. Even at 20 kHz, as you know the lowest frequency of the harmonics is 40 kHz. Above that, even dogs, including the OCD ones, are not going to complain:

The point is, 100 dB SINAD being way beyond human hearing threshold is not a definite thing, especially when frequency, and the harmonic contributing harmonics are not specified, but the hearing threshold for the high frequency well above 20 kHz, such as your suggested 40 kHz (2nd harmonic of 20 kHz) is not even debatable, as far as I am aware.

From Wiki:

1694538753570.png
 
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Dear @restorer-john

Per our recent discussions, I have conducted comprehensive tests with two NCx500 modules incorporated into our Apollon NCx500 DM dual mono amplifier. In order to rigorously assess their performance, I subjected the NCx500 to demanding conditions: running them continuously for 5 minutes at 20kHz over 500 watts into a resistive 4Ohm load (0.001 THD+N), and at 1kHz over 500 watts into a 4Ohm resistive load (0.1 THD+N).

I'm pleased to report that the amplifier performed exceptionally, maintaining 500 watts at 20kHz for the entire 5-minute duration. Interestingly, the NCx500 modules exhibited lower temperature increases at 20kHz compared to 1kHz. After the test, the NCx500 modules reached temperatures of 60 degrees Celsius (140 degrees Fahrenheit), while the Hypex SMPS 1200 power supplies and the enclosure maintained a consistent 30 degrees Celsius (86 degrees Fahrenheit).

To further align with FTC standards, the amplifier was preconditioned at one-eighth of its rated total power output for one hour using a 1,000 Hz sinusoidal wave.

Through this examination, I hope to conclusively demonstrate the robust capabilities of class D amplifier modules, particularly in response to skepticism about their performance at higher frequencies. The modules in the test were housed in a 2.5mm thick enclosure. Given this, it's exciting to contemplate their potential performance in our more robust 10mm enclosures or within our premium amplifiers, which feature expansive heat sinks.

Reflecting upon the capabilities showcased, I am compelled to ask: who might require power beyond what this offers? This isn't merely a powerful amplifier; it stands as a testament to unparalleled power, delivering remarkable performance, especially when considering its compact form, weight, affordable price and efficiency.



In light of your valuable feedback, I concur that our website should provide more detailed specifications showcasing the true prowess of our amplifiers. Not doing so would indeed undersell their capabilities. Rest assured, we will be updating this information shortly.

Thank you for your insightful suggestions and unwavering support.

I appreciate the information, but I don't think @restorer-john is suggesting your products can't achieve those performance level, but was suggesting that your published website information does not provide such details. It would probably help if you include the information in the specifications published on your website, data sheet, owner's manuals etc. It may attract more customers and increase our wait time so that's could be a negative for the potential customers lol..

By the way, since you have the AP, is it possible for you to do a FFT not using 1 kHz test signal, but say, 5 kHz, or even 10 kHz. I keep thinking above since no reviewers has published such FFT, how can we be sure that the harmonics profile don't get worse or even much worse than that reviewed by the FFTs using 1 kHz test frequency. Or it is because the AP does not have the capability to plot FFT at such high test frequency? Thank you in advance.
 
I appreciate the information, but I don't think @restorer-john is suggesting your products can't achieve those performance level, but was suggesting that your published website information does not provide such details. It would probably help if you include the information in the specifications published on your website, data sheet, owner's manuals etc. It may attract more customers and increase our wait time so that's could be a negative for the potential customers lol..

By the way, since you have the AP, is it possible for you to do a FFT not using 1 kHz test signal, but say, 5 kHz, or even 10 kHz. I keep thinking above since no reviewers has published such FFT, how can we be sure that the harmonics profile don't get worse or even much worse than that reviewed by the FFTs using 1 kHz test frequency. Or it is because the AP does not have the capability to plot FFT at such high test frequency? Thank you in advance.
The statement from @restorer-john was: "Peak or continuous power at 1kHz has always been a cop-out for amplifiers incapable of delivering their rated continuous power across the audible bandwidth. Because amplifiers back in the day (and plenty now) could not produce their rated power at frequency extremes. It's always been the "realm" (your word) of manufacturers who attempt to game the system with smoke and mirrors. It was one of the main reasons the Amplifier Rule was created and enforced in the first place!"

Smoke and mirrors? :facepalm:

Certainly, I will proceed with measurements at the elevated frequencies as requested. Let me know if there are any additional specifics you'd like addressed.
 
Per our recent discussions, I have conducted comprehensive tests with two NCx500 modules incorporated into our Apollon NCx500 DM dual mono amplifier. In order to rigorously assess their performance, I subjected the NCx500 to demanding conditions: running them continuously for 5 minutes at 20kHz over 500 watts into a resistive 4Ohm load (0.001 THD+N), and at 1kHz over 500 watts into a 4Ohm resistive load (0.1 THD+N).

I'm pleased to report that the amplifier performed exceptionally, maintaining 500 watts at 20kHz for the entire 5-minute duration. Interestingly, the NCx500 modules exhibited lower temperature increases at 20kHz compared to 1kHz. After the test, the NCx500 modules reached temperatures of 60 degrees Celsius (140 degrees Fahrenheit), while the Hypex SMPS 1200 power supplies and the enclosure maintained a consistent 30 degrees Celsius (86 degrees Fahrenheit).

To further align with FTC standards, the amplifier was preconditioned at one-eighth of its rated total power output for one hour using a 1,000 Hz sinusoidal wave.
:cool:
R-E-S-P-E-C-T
 
The statement from @restorer-john was: "Peak or continuous power at 1kHz has always been a cop-out for amplifiers incapable of delivering their rated continuous power across the audible bandwidth. Because amplifiers back in the day (and plenty now) could not produce their rated power at frequency extremes. It's always been the "realm" (your word) of manufacturers who attempt to game the system with smoke and mirrors. It was one of the main reasons the Amplifier Rule was created and enforced in the first place!"

Smoke and mirrors? :facepalm:

Certainly, I will proceed with measurements at the elevated frequencies as requested. Let me know if there are any additional specifics you'd like addressed.

Only because you ask, I would add the one requested by @CleanSound on Amir. I suspectd Amir has already returned the DUT to it's owner, so there is no chance for him to do the 20 kHz test frequency graph even if he has time to do it.

So, I assume CleanSound wants to do the following one but with test frequency 20 kHz, Amir stopped at 15 kHz. He even admitted it is just for "OCD" so if you are kind enough to do it, I think people just want to see it once, no need to even do it again..:D

You probably would increase the bandwidth to the next step above 45 kHz, I assume..

index.php


The curve will be expectedly uglier, but I think no one will complain if your graph emphasizes the ugliness is due to noise and distortions in the ultrasonic range.

And for the FFT, it would be like the following it, but test freq 10 kHz, or at least 5 kHz, if possible:



index.php


Thanks again.
 
Dear @restorer-john

Per our recent discussions, I have conducted comprehensive tests with two NCx500 modules incorporated into our Apollon NCx500 DM dual mono amplifier. In order to rigorously assess their performance, I subjected the NCx500 to demanding conditions: running them continuously for 5 minutes at 20kHz over 500 watts into a resistive 4Ohm load (0.001 THD+N), and at 1kHz over 500 watts into a 4Ohm resistive load (0.1 THD+N).

I'm pleased to report that the amplifier performed exceptionally, maintaining 500 watts at 20kHz for the entire 5-minute duration. Interestingly, the NCx500 modules exhibited lower temperature increases at 20kHz compared to 1kHz. After the test, the NCx500 modules reached temperatures of 60 degrees Celsius (140 degrees Fahrenheit), while the Hypex SMPS 1200 power supplies and the enclosure maintained a consistent 30 degrees Celsius (86 degrees Fahrenheit).

To further align with FTC standards, the amplifier was preconditioned at one-eighth of its rated total power output for one hour using a 1,000 Hz sinusoidal wave.

Through this examination, I hope to conclusively demonstrate the robust capabilities of class D amplifier modules, particularly in response to skepticism about their performance at higher frequencies and continuous power. The modules in the test were housed in a 2.5mm thick enclosure. Given this, it's exciting to contemplate their potential performance in our more robust 10mm enclosures or within our premium amplifiers, which feature expansive heat sinks.

Reflecting upon the capabilities showcased, I am compelled to ask: who might require power beyond what this offers? This isn't merely a powerful amplifier; it stands as a testament to unparalleled power, delivering remarkable performance, especially when considering its compact form, weight, affordable price and efficiency.

For optimal clarity, kindly ensure that the video quality on YouTube is set to 1080p or 720p.



In light of your valuable feedback, I concur that our website should provide more detailed specifications showcasing the true prowess of our amplifiers. Not doing so would indeed undersell their capabilities. Rest assured, we will be updating this information shortly.

Thank you for your insightful suggestions and unwavering support.

Only the "like" isn't enough ... let me applaud. Thank you sir.
 
The statement from @restorer-john was: "Peak or continuous power at 1kHz has always been a cop-out for amplifiers incapable of delivering their rated continuous power across the audible bandwidth. Because amplifiers back in the day (and plenty now) could not produce their rated power at frequency extremes. It's always been the "realm" (your word) of manufacturers who attempt to game the system with smoke and mirrors. It was one of the main reasons the Amplifier Rule was created and enforced in the first place!"

Smoke and mirrors? :facepalm:

Certainly, I will proceed with measurements at the elevated frequencies as requested. Let me know if there are any additional specifics you'd like addressed.
I think that Apollon deserves credit for continuing to provide patient, thoughtful replies while basically being attacked for delivering high quality products and service at great prices.

Some of the negative opinions expressed here should really be directed at Hypex / Purifi and Class-D as an amplification topology in general rather than @ Apollon as a company.
 
The statement from @restorer-john was: "Peak or continuous power at 1kHz has always been a cop-out for amplifiers incapable of delivering their rated continuous power across the audible bandwidth. Because amplifiers back in the day (and plenty now) could not produce their rated power at frequency extremes. It's always been the "realm" (your word) of manufacturers who attempt to game the system with smoke and mirrors. It was one of the main reasons the Amplifier Rule was created and enforced in the first place!"

Smoke and mirrors? :facepalm:

Certainly, I will proceed with measurements at the elevated frequencies as requested. Let me know if there are any additional specifics you'd like addressed.
Too be fair to @restorer-john, he is pointing out a legitimate reason why he wanted 20kHz. And he also pointed out the reason why (most) manufacturers don't do it.

But the wording did come across as lumping Apollon with other manufacturers who intentionally don't do 20kHz.

Either way, this amp is a win for consumers. Although, the dual mono, Lux version is on the pricier side. But I guess, after how Apollon showed up here, they may have earned it.
 
So, I assume CleanSound wants to do the following one but with test frequency 20 kHz, Amir stopped at 15 kHz. He even admitted it is just for "OCD" so if you are kind enough to do it, I think people just want to see it once, no need to even do it again..:D
???

Actually, until this review, I ran the test up to 20 kHz. I do not show it because the measurement is misleading as it under-represents the level of distortion due to limited bandwidth of 45 kHz. Here is the sweep from the amp I tested before this one with 20 kHz now highlighted in red:

1694544460708.png


Notice how it is much lower value than 10 and 15 kHz (blue and green) which obviously is not correct. 45 kHz only allows one harmonic to be included in the computation of THD whereas we have 2 to 3 in 10 and 5 kHz respectively.

You might say that measurement bandwidth should be expanded to include more harmonics. We had this argument at length when I first introduced this test. If I increase the bandwidth, it will suck in the noise shaping that occurs in class D amp. That would cause people to then think there is distortion when in reality it is ultrasonic noise. You can see this in the spectrum of Purifi amplifier:

index.php


Notice how noise level increases as we approach 100 kHz. Even at 45 kHz I am probably picking up some of that and with it, disadvantaging class D amps a bit.

Net, net, this is a difficult test to get right and we are the only outfit that is running it against every amp right now. It gives us insight into the transfer function of amplifier at multiple frequencies so the criticism that we only focus on 1 kHz is flat wrong.

Note that the wiggles you see in class D amps like this are more highlighted due to their very low noise. If noise were higher, it would mask them and graphs would look much smoother.
 
???

Actually, until this review, I ran the test up to 20 kHz. I do not show it because the measurement is misleading as it under-represents the level of distortion due to limited bandwidth of 45 kHz. Here is the sweep from the amp I tested before this one with 20 kHz now highlighted in red:

View attachment 311540

Notice how it is much lower value than 10 and 15 kHz (blue and green) which obviously is not correct. 45 kHz only allows one harmonic to be included in the computation of THD whereas we have 2 to 3 in 10 and 5 kHz respectively.

You might say that measurement bandwidth should be expanded to include more harmonics. We had this argument at length when I first introduced this test. If I increase the bandwidth, it will suck in the noise shaping that occurs in class D amp. That would cause people to then think there is distortion when in reality it is ultrasonic noise. You can see this in the spectrum of Purifi amplifier:

index.php


Notice how noise level increases as we approach 100 kHz. Even at 45 kHz I am probably picking up some of that and with it, disadvantaging class D amps a bit.

Net, net, this is a difficult test to get right and we are the only outfit that is running it against every amp right now. It gives us insight into the transfer function of amplifier at multiple frequencies so the criticism that we only focus on 1 kHz is flat wrong.

Note that the wiggles you see in class D amps like this are more highlighted due to their very low noise. If noise were higher, it would mask them and graphs would look much smoother.
Thanks, now I remember.. seems like 15 kHz is a better limit especially for class D amps. I actually think 10 kHz is enough, and it wasn't me who suggested the 20 kHz test.
 
Too be fair to @restorer-john, he is pointing out a legitimate reason why he wanted 20kHz. And he also pointed out the reason why (most) manufacturers don't do it.
He is not fair. He has read the datasheet so he should very well know that these class D amps come with level of documentation and measurements that no traditional audio company provides. Here is the very thing he is asking about from Hypex NC500 datasheet:

1694545248713.png


Yes, the graph is wrong above 10 khz due to the same limitation in bandwidth but as I noted about the amps he post, who knows how they made their measurements.
 
Only because you ask, I would add the one requested by @CleanSound on Amir. I suspectd Amir has already returned the DUT to it's owner, so there is no chance for him to do the 20 kHz test frequency graph even if he has time to do it.

So, I assume CleanSound wants to do the following one but with test frequency 20 kHz, Amir stopped at 15 kHz. He even admitted it is just for "OCD" so if you are kind enough to do it, I think people just want to see it once, no need to even do it again..:D

You probably would increase the bandwidth to the next step above 45 kHz, I assume..

index.php


The curve will be expectedly uglier, but I think no one will complain if your graph emphasizes the ugliness is due to noise and distortions in the ultrasonic range.

And for the FFT, it would be like the following it, but test freq 10 kHz, or at least 5 kHz, if possible:



index.php


Thanks again.
Here you go:


Bench 1kHz 4Ohm .png

Bench 5kHz 4Ohm .png

Bench 10kHz 4Ohm .png

Bench 15kHz 4Ohm .png

Bench 20kHz 4Ohm .png

THD+N vs Measured Level 4Ohm.png
 
Many thanks! This amp is super clean, do you ship to Canada? Wonder what the shipping and import duty would cost, in addition to our HST, harmonize sales tax.:D
I hope you will include such test data on your website, that will for sure keep the OCD type happier.;)
You are very welcome. We offer global shipping. Kindly be advised that the measurements provided pertain to the NCx500 DM dual mono version, which I have readily available in my studio. At this moment, I do not have the smaller NCx500ST version with one power supply on hand. The distinguishing feature of the dual mono version is that each NCx500 module is paired with its own dedicated Hypex SMPS1200 power supply.

We recognize the importance of these details for our customers, and thus we are in the process of updating our website to incorporate this information. It will also be included in forthcoming manuals. We appreciate your patience as we enhance our online presence.
 
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