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IOM 500s Stereo Amplifier Review

Rate this amplifier:

  • 1. Poor (headless panther)

    Votes: 4 2.0%
  • 2. Not terrible (postman panther)

    Votes: 35 17.7%
  • 3. Fine (happy panther)

    Votes: 134 67.7%
  • 4. Great (golfing panther)

    Votes: 25 12.6%

  • Total voters
    198

amirm

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This is a review and detailed measurements of the IOM 500 Hypex NCx500 class D based stereo amplifier. It was sent to me by the company and costs €1,099.00 ex VAT (US $1,199).
IOM 500s Stereo Hypex NCx500 class D amplifier review.jpg

We have a more premium case for the class with good bit of weight. The amplifier comes with both fixed or variable gain. The latter is what I have for testing:
IOM 500s Stereo Hypex NCx500 class D amplifier review back panel adjustable gain.jpg

I like the hefty weight and solid feel of the gain selector but it is squeezed tight between binding posts, making it hard to turn. It has a wide range of 11 dB to 34 which is very convenient as far as matching to the source output voltage. I tested it at 11 and 16 dB as you see below.

IOM 500 Stereo Amplifier Measurements
I started with the lowest gain which matches the Hypex NCx500 reference design:
IOM 500 Stereo Hypex NCx500 class D amplifier gain 11 measurement.png


While performance is a few dBs short of reference, it is still excellent enough to land in the middle of the top 20 amplifiers ever tested:
Best hypex class d stereo amplifier review.png

Naturally there is some loss when you increase gain:
IOM 500 Stereo Hypex NCx500 class D amplifier gain 16 measurement.png

For some reason though, the differential in SINAD between channels increases as gain is increased. I played with the wiring but could not resolve this.

Using RCA output made things much worse:
IOM 500 Stereo Hypex NCx500 class D amplifier gain 16 RCA measurement.png


So I stayed with balanced input for rest of the measurements:
IOM 500 Stereo Hypex NCx500 class D amplifier gain 16 SNR measurement.png

Left side says you have full transparency at just 5 watts for 16 or even 17 bit content! And at full power, you have better dynamic range than any content you are likely to have.

Frequency response is load independent and excellent:
IOM 500 Stereo Hypex NCx500 class D amplifier gain 16 frequency response measurement.png


But for crosstalk, it is not as good as I expected:
IOM 500 Stereo Hypex NCx500 class D amplifier gain 16 crosstalk measurement.png


Intermodulation distortion is kept very low:
IOM 500 Stereo Hypex NCx500 class D amplifier gain 16 Multitone measurement.png


IOM 500 Stereo Hypex NCx500 class D amplifier gain 16 19 20 kHz intermodulation distortion mea...png


Name of the game here is lots of power and indeed, that is what we get:
IOM 500 Stereo Hypex NCx500 class D amplifier Power 4 ohm measurement.png


Allowing 1% THD, gets us even more:
IOM 500 Stereo Hypex NCx500 class D amplifier Max Peak Power 4 ohm measurement.png


I wanted to add low frequency power measurements using the same metric and noticed that only 50 Hz is supported in CEA-2006/490A so went with that for both max and peak power:
IOM 500 Stereo Hypex NCx500 class D amplifier Max Peak Power 4 ohm 50 Hz measurement.png


So you lose about 15%. Here is 8 ohm performance:

IOM 500 Stereo Hypex NCx500 class D amplifier gain 16 Power 8 ohm measurement.png


Sweeping at different frequencies, I see more noise at 20 and 500 Hz at lower levels:
IOM 500 Stereo Hypex NCx500 class D amplifier Power 4 ohm vs frequency measurement.png



Warm up showed variable response until it stabilized:
IOM 500 Stereo Hypex NCx500 class D amplifier warm up measurement.png


Finally, power on noise is kept in check but turning off, many create noise:
IOM 500 Stereo Hypex NCx500 class D amplifier Power on noise measurement.png


We see the same warm up effect in one channel even though the amplifier was warm when I ran this test.

Conclusions
The IOM 500s is built on the excellent "bones" of the Hypex NCx500 OEM amplifier modules and it shows. Addition of a selectable gain stage has boosted distortion and noise a bit which could use some refinement. But as is, I expect the amplifier to be very powerful to drive any speaker and do so with minimum of noise and distortion if you use XLR. RCA performance may not keep up.

I am going to recommend IOM 500 stereo class D amplifier.
----------
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/
 
Without digging through older tests, it seems like this otherwise performant device takes an unusually big hit when switching from balanced to single-ended input.
 
For similar price the Apollon NCx500ST still seems to be the best option.

 
Overall good watts / dollar here, as expected, but I am surprised at the penalty for using RCA. Can't remember seeing another hypex amp do so poorly on that metric.
 
This is a review and detailed measurements of the IOM 500 Hypex NCx500 class D based stereo amplifier. It was sent to me by the company and costs €1,099.00 ex VAT (US $1,199).
View attachment 384660
We have a more premium case for the class with good bit of weight. The amplifier comes with both fixed or variable gain. The latter is what I have for testing:
View attachment 384661
I like the hefty weight and solid feel of the gain selector but it is squeezed tight between binding posts, making it hard to turn. It has a wide range of 11 dB to 34 which is very convenient as far as matching to the source output voltage. I tested it at 11 and 16 dB as you see below.

IOM 500 Stereo Amplifier Measurements
I started with the lowest gain which matches the Hypex NCx500 reference design:
View attachment 384662

While performance is a few dBs short of reference, it is still excellent enough to land in the middle of the top 20 amplifiers ever tested:
View attachment 384664
Naturally there is some loss when you increase gain:
View attachment 384665
For some reason though, the differential in SINAD between channels increases as gain is increased. I played with the wiring but could not resolve this.

Using RCA output made things much worse:
View attachment 384666

So I stayed with balanced input for rest of the measurements:
View attachment 384667
Left side says you have full transparency at just 5 watts for 16 or even 17 bit content! And at full power, you have better dynamic range than any content you are likely to have.

Frequency response is load independent and excellent:
View attachment 384669

But for crosstalk, it is not as good as I expected:
View attachment 384670

Intermodulation distortion is kept very low:
View attachment 384671

View attachment 384672

Name of the game here is lots of power and indeed, that is what we get:
View attachment 384674

Allowing 1% THD, gets us even more:
View attachment 384675

I wanted to add low frequency power measurements using the same metric and noticed that only 50 Hz is supported in CEA-2006/490A so went with that for both max and peak power:
View attachment 384676

So you lose about 15%. Here is 8 ohm performance:

View attachment 384677

Sweeping at different frequencies, I see more noise at 20 and 500 Hz at lower levels:
View attachment 384678


Warm up showed variable response until it stabilized:
View attachment 384679

Finally, power on noise is kept in check but turning off, many create noise:
View attachment 384680

We see the same warm up effect in one channel even though the amplifier was warm when I ran this test.

Conclusions
The IOM 500s is built on the excellent "bones" of the Hypex NCx500 OEM amplifier modules and it shows. Addition of a selectable gain stage has boosted distortion and noise a bit which could use some refinement. But as is, I expect the amplifier to be very powerful to drive any speaker and do so with minimum of noise and distortion if you use XLR. RCA performance may not keep up.

I am going to recommend IOM 500 stereo class D amplifier.
----------
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/
Can you do more rca testing? That's a major way of connecting amps....
 
Looks like too much squeezed into too little of a box. I WOULD like to see a review of their mono w/ power meter (if it still exists) with the current NCx500 module and an in-box separate power supply.
 
Last edited:
Considering the fact that it was tested with very low gain (16dB) that always favors results I wouldn't call this assembly successful.

The 15% penalty in power at 50Hz is not a good sign and it needs more investigation even lower than that (all the way down to 20Hz) as this is where the big chunk of power is needed.
Some mood for fun,some EQ,a little bigger room and listening distance and bass heavy music can drain large amounts down there with big speakers and no sub.

Otherwise,nice case despite the small factor.

Thanks Amir!
 
I'm not so sure, If we compare
Yeah it clearly could be cleaned up a little... not much space left in that case. That is why I didn't say excellent, only good. Seems to be a small issue with Ch2 as well and a bit of PSU noise, but certainly at very low levels. Still, as you show in comparison it could be improved.


JSmith
 
Yeah it clearly could be cleaned up a little... not much space left in that case. That is why I didn't say excellent, only good. Seems to be a small issue with Ch2 as well and a bit of PSU noise, but certainly at very low levels. Still, as you show in comparison it could be improved.


JSmith
The RCA mess is only with 16dB gain.
How would that measure when used after an AVR with weak pre-outs for example where 32dB gain would be needed?
It seems as there's something broken in there.
 
Is a reactive load test still possible?
I am quite far behind in reviews but I will see what I can do....
 
Maybe no excuse today, but the RCA performance is still at least as good as what we regarded as 'very good' performance forty years back when the higher end was becoming established! I do appreciate that for some readers here, forty to fifty years back is Jurassic times, but the HiFi industry was thriving then and a lot of gear was being sold, just to put things in perspective. Only 'criticism' I could possibly offer on the distortion spectra is how 'lumpy' it seems to be, despite the XLR levels being all but vanishingly low. Maybe a lack of noise shows it and makes it look worse, I don't know.

Cases look solid though, so visually quite elegant and attractive. Put together and from The Netherlands it seems, so maybe mostly of interest to us in and around Europe?
 
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