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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 1.0%
  • 3. Fine (happy panther)

    Votes: 30 7.2%
  • 4. Great (golfing panther)

    Votes: 377 91.1%

  • Total voters
    414

amirm

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This is a review and detailed measurements of the Apollon NCx500ST stereo class D amplifier based on Hypex NCOREx NCx500 modules. It was kindly drop shipped from the member and costs 1,090.00€ (US $1,168) with standard opamp.

Apollo NCx500ST stereo class D amplifier hypex NCOREx NCx500 review.jpg

While the case is stamped aluminum, it is a heavily customized one with attractive side vents. You get to select your color of choice. The back panel is where you notice the high value add:

Apollo NCx500ST stereo class D amplifier hypex NCOREx NCx500 back panel gain switch review.jpg

You have no less than four gain settings and even an LED brightness switch! FYI, I will have to confirm which op-amp is included with this sample.
EDIT: the default TI OPA1612 op-amp was in this sample.
EDIT 2: turns the amp used Sonic Imagery op-amps (by mistake).

To make sure I didn't go mad given the combination of input types and four gain settings, I stayed with XLR testing.

If you are not familiar with the tests that are about to follow, please watch my video on understanding amplifier measurements.

Edit: just realized I left out the "n" out of the name on all the notations. :(

Apollon NCx500ST Amplifier Measurement
I started with the lowest gain setting:
Apollo NCx500ST stereo class D amplifier hypex NCOREx NCx500 lowest gain measurement.png

While just a couple of dBs shy of the reference design, performance is good enough to easily land in our top 10 best amplifiers tested:
best class d stereo amplifier review.png

You need a ton of input voltage to get max power in this low gain setting so let's step up through the gain settings:
Apollo NCx500ST stereo class D amplifier hypex NCOREx NCx500 medium gain measurement.png


Apollo NCx500ST stereo class D amplifier hypex NCOREx NCx500 medium high gain measurement.png

Apollo NCx500ST stereo class D amplifier hypex NCOREx NCx500 high gain measurement.png


You can see the benefit of low gain in am amplifier for best noise performance especially since the dynamic range of the DAC improves as well with higher output.

Here are two SNR measurements:
Apollo NCx500ST stereo class D amplifier hypex NCOREx NCx500 lowest gain SNR measurement.png


I picked next to highest gain because it lets you drive it to max power with less than 4 volts on XLR:
Apollo NCx500ST stereo class D amplifier hypex NCOREx NCx500 medium high gain SNR measurement.png


In that reward, it would have been nice to have a different gain level optimized for 4 volts output from the source (here, we jump from 2.1 to 5 volts).

Notice how channel separation is also gain sensitive:
Apollo NCx500ST stereo class D amplifier hypex NCOREx NCx500 channel separation measurement.png


Frequency response is expectedly excellent and load independent:
Apollo NCx500ST stereo class D amplifier hypex NCOREx NCx500 frequency response measurement.png


Intermodulation is kept to very low levels:
Apollo NCx500ST stereo class D amplifier hypex NCOREx NCx500 lowest gain Multitone measurement.png

Apollo NCx500ST stereo class D amplifier hypex NCOREx NCx500 lowest gain 19 20 kHz measurement.png


This is one powerful amplifier:
Apollo NCx500ST stereo class D amplifier hypex NCOREx NCx500 lowest gain Power 4 ohm measurement.png

Apollo NCx500ST stereo class D amplifier hypex NCOREx NCx500 lowest gain max and peak Power 4 ...png


Apollo NCx500ST stereo class D amplifier hypex NCOREx NCx500 lowest gain Power 8 ohm measurement.png


The amp has a very robust protection circuit and did not mind at all being pushed way beyond clipping. This made it easy to measure with PowerCube:
Apollo NCx500ST stereo class D amplifier hypex NCOREx NCx500 lowest gain Reactive Power measur...png


An ideal amp would keep its voltage constant regardless of load. We almost have that at 4 ohm but at 2 ohms, the required current goes through the roof and output droops. Lest you get depressed about that, check out the amount of power you are getting:
Apollo NCx500ST stereo class D amplifier hypex NCOREx NCx500 lowest gain Reactive Power Watts ...png


For a moment, it produced 2.2 Killowatts on my 20 amp circuit! I should mention that I have modified these tests for burst rather than continuous power. With continues output, it is very easy to push the Powercube beyond its specs. The burst nature is the reason so much power was to be had at that 2 ohm load setting.

Anyway, the amplifier is extremely robust and doesn't care how difficult the load is.

Distortion is kept at a minimum at or below 1 kHz:
Apollo NCx500ST stereo class D amplifier hypex NCOREx NCx500 lowest gain Power 4 ohm vs freque...png

BTW, this test is also updated to have more frequencies represented than before (addition of 200 Hz).

Amplifier is stable on power up:
Apollo NCx500ST stereo class D amplifier hypex NCOREx NCx500  warm up measurement.png


And is extremely quiet on power on/off:
Apollo NCx500ST stereo class D amplifier hypex NCOREx NCx500 power on off noise measurement.png


Conclusions
The Apollon NCx500ST is a clear value added class D amplifier with lots of features compared to reference design. It gives up just a few dBs of noise performance but still manages to rank #6 in our list giving you confidence of transparency while producing copious amount of power. It is also easily sourced in Europe which is a benefit for many of our readers.

I am happy to put the Apollon NCx500ST amplifier on my recommended list.

Manufacturer Specifications:

Frequency Response: 0 – 70k Hz +0/-3dB
Low Distortion: THD+N – – 0.0002 % 20Hz-20kHz
High Input Impedance 50K
Signal to noise ratio: 137dB
Gain (dB) 12,8/20,5/27,5/29
Ultra High Damping Factor
High Current Output
Power rating: 675W @ 2ohm | 650W @ 4ohm | 380W @ 8ohm
Case Dimensions: 350mm depth x 90mm height (with feet) x 280 mm width
Weight: 2.9 kg

-----------
As always, questions, comments, recommendations, etc. are welcome.

Any donations are much appreciated using: https://www.audiosciencereview.com/forum/index.php?threads/how-to-support-audio-science-review.8150/
 
Last edited:
Wow! If I hadn't switched to active speakers this would've absolutely been my amp -- switchable gains (love that about pro amps, gain controls can be a lifesaver for noise issues), a trigger input and pass-through, balanced and unbalanced... and it measures really well!

Hats off to the designers, looks like an excellent piece of kit.
 
It was kindly drop shipped from the member and costs 1,090.00€ (US $1,168) with standard opamp.
A decent price for this level of SOTA performance and power. Thanks to whoever sent this one in and @amirm for the testing.

The case, connectors and design in general seem most professional. It's good to see XLR and RCA too as well as the gain settings. Also, @Apollon Audio nice job. :)

Apollon-Hypex-NCx500-Stereo-Amplifier-Inside-Isometric.webp


Apollon-Hypex-NCx500-Stereo-Amplifier-Sonic-Imagery-OPamp-rolling.webp



JSmith
 
Sleek and stylish no-nonsense amp, and not even expensive in its class. I probably would buy this one if I needed one.

A kind of a Q.E.D., proving that:
  • good amplification does not have to cost "an arm and a leg"
  • good design is possible with simple means / materials.
Great.
 
Wow! If I hadn't switched to active speakers this would've absolutely been my amp -- switchable gains (love that about pro amps, gain controls can be a lifesaver for noise issues), a trigger input and pass-through, balanced and unbalanced... and it measures really well!

Hats off to the designers, looks like an excellent piece of kit.
And looks nice :) Simply, but nice.
 
Game changer in this assembly (apart from performance) is the ability to adapt to any need (RCA or XLR,each with it's own choice of gains.
Back panel oozes quality.I love the fact that connections are also bolted on case,not only soldered on pcb so the later doesn't get the stress when connecting stuff.

Thanks Amir!
 
good design is possible with simple means / materials.
If you are willing to say that extremely advanced class D modules that only 2 companies in the world know how to make are simple that is.
 
This is a review and detailed measurements of the Apollon NCx500ST stereo class D amplifier based on Hypex NCOREx NCx500 modules. It was kindly drop shipped from the member and costs 1,090.00€ (US $1,168) with standard opamp.

View attachment 310220
While the case is stamped steel, it is a heavily customized one with attractive side vents. You get to select your color of choice. The back panel is where you notice the high value add:

View attachment 310221
You have no less than four gain settings and even an LED brightness switch! FYI, I will have to confirm which op-amp is included with this sample.

To make sure I didn't go mad given the combination of input types and four gain settings, I stayed with XLR testing.

If you are not familiar with the tests that are about to follow, please watch my video on understanding amplifier measurements.

Edit: just realized I left out the "n" out of the name on all the notations. :(

Apollon NCx500ST Amplifier Measurement
I started with the lowest gain setting:
View attachment 310222
While just a couple of dBs shy of the reference design, performance is good enough to easily land in our top 10 best amplifiers tested:
View attachment 310223
You need a ton of input voltage to get max power in this low gain setting so let's step up through the gain settings:
View attachment 310224

View attachment 310225
View attachment 310226

You can see the benefit of low gain in am amplifier for best noise performance especially since the dynamic range of the DAC improves as well with higher output.

Here are two SNR measurements:
View attachment 310227

I picked next to highest gain because it lets you drive it to max power with less than 4 volts on XLR:
View attachment 310228

In that reward, it would have been nice to have a different gain level optimized for 4 volts output from the source (here, we jump from 2.1 to 5 volts).

Notice how channel separation is also gain sensitive:
View attachment 310230

Frequency response is expectedly excellent and load independent:
View attachment 310229

Intermodulation is kept to very low levels:
View attachment 310231
View attachment 310232

This is one powerful amplifier:
View attachment 310233
View attachment 310234

View attachment 310235

The amp has a very robust protection circuit and did not mind at all being pushed way beyond clipping. This made it easy to measure with PowerCube:
View attachment 310236

An ideal amp would keep its voltage constant regardless of load. We almost have that at 4 ohm but at 2 volts, the required current goes through the roof and output droops. Lest you get depressed about that, check out the amount of power you are getting:
View attachment 310237

For a moment, it produced 2.2 Killowatts on my 20 amp circuit! I should mention that I have modified these tests for burst rather than continuous power. With continues output, it is very easy to push the Powercube beyond its specs. The burst nature is the reason so much power was to be had at that 2 ohm load setting.

Anyway, the amplifier is extremely robust and doesn't care how difficult the load is.

Distortion is kept at a minimum at or below 1 kHz:
View attachment 310238
BTW, this test is also updated to have more frequencies represented than before (addition of 200 Hz).

Amplifier is stable on power up:
View attachment 310239

And is extremely quiet on power on/off:
View attachment 310240

Conclusions
The Apollon NCx500ST is a clear value added class D amplifier with lots of features compared to reference design. It gives up just a few dBs of noise performance but still manages to rank #6 in our list giving you confidence of transparency while producing copious amount of power. It is also easily sourced in Europe which is a benefit for many of our readers.

I am happy to put the Apollon NCx500ST amplifier on my recommended list.

-----------
As always, questions, comments, recommendations, etc. are welcome.

Any donations are much appreciated using: https://www.audiosciencereview.com/forum/index.php?threads/how-to-support-audio-science-review.8150/
Excellent, and made in Europe (Slovenia). They also make amps with very nice casework <https://apollonaudio.com/apollon-audio-amplifiers/>.
 
I notice that Apollon indicates the following at their website: THD+N – – 0.0002 % 20Hz-20kHz. It seems this has not been met here?
How would you compare this with the Audiophonics equivalents (HPA-S600NCX and LPA-S600NCX)? Those seem to have quite lower specifications:
Typ : 0.0006%
Max : 0.001%
 
I don't like the curved side corners. Not a major flaw, just not good industrial design IMHO.

The more I see class-D amps filling the top ranks of the amplifier ratings, the more respect I have for Benchmark in designing a class AB amp that is right up there with them. I think class AB design and manufacturing to that exalted standard is very difficult. Seems to me that once the methods for top-quality class D amps have been worked out, it's somewhat easier to achieve this level of performance - especially if you are going to use a Hypex or Purifi module.

Good amps all sound good. I don't think there's an inherent sonic advantage in choosing class-D or class-AB; but class-D does have power consumption, weight and heat advantages over traditional class-AB designs.
 
Good amps all sound good. I don't think there's an inherent sonic advantage in choosing class-D or class-AB; but class-D does have power consumption, weight and heat advantages over traditional class-AB designs.
And the most important factor for a power amp: power.
Yep,top 2 ones are AB's (Topping) but power delivery may not be enough to meet the peaks if anyone wants high levels.
 
This seems incredibly solid and a ton of power if required. The pricing (even including VAT) seems more than reasonable, especially considering that it's EU made so you have some sort of customer protection laws there. Good job to the Apollon team.

Thanks for taking the time to measure it Amir and thanks to whichever reader sent this in!
 
I don't like the curved side corners. Not a major flaw, just not good industrial design IMHO.

The more I see class-D amps filling the top ranks of the amplifier ratings, the more respect I have for Benchmark in designing a class AB amp that is right up there with them. I think class AB design and manufacturing to that exalted standard is very difficult. Seems to me that once the methods for top-quality class D amps have been worked out, it's somewhat easier to achieve this level of performance - especially if you are going to use a Hypex or Purifi module.

Good amps all sound good. I don't think there's an inherent sonic advantage in choosing class-D or class-AB; but class-D does have power consumption, weight and heat advantages over traditional class-AB designs.
I agree about the casework. I can't explain it, but it just looks cheap, even if it's perfectly functional and well finished. The good news is that they also make amps with very nice casework (see link in my previous post).
 
Thanks !
Very interesting amplifier, at this price.

The price you listed in € is without VAT.
When shipping to Belgium with UPS, with VAT, it raises up to 1416€.

Would be good if they offer destination vat option. The 22% they apply is higher than many other countries. Think giant Germany. Makes +30 eur difference with German 19%. For me it would be >60eur difference
 
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