IOM 500s Stereo Amplifier Review

[JeremyFife]

Thanks for the review, this is an attractive price point for upgrading (from my point of view).

I'm left slightly disappointed, expecting too much perhaps: drop off in performance with RCA, some channel imbalance, potential distortion issues at frequency extremes (just 20-20k, not sub/super frequencies). Good amount of power though.

Personally, I like the small form case. However, that back panel does look cluttered and short on space - a few extra mm would have helped. Does anyone have concerns about thermal issues in that small space?

Overall, I'm left slightly uneasy / underwhelmed. I wanted to like this more.

 

[Ajax]

For similar price the Apollon NCx500ST still seems to be the best option.

Apollon NCx500ST Stereo Amplifier Review

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. While the case is stamped aluminum, it is a heavily customized one...

www.audiosciencereview.com

Hi Matias,

Amir's review of the Apollon implementation of the same module confirms your thoughts, as it is superior to IOM's effort in nearly every measurement.

 

[AndreaT]

I wonder if two more inches of breathing space could have helped to lower the noise. On the guts’pic the main line is very close to one of the amp modules. While a small enclosure is commendable, a too small one is not.
Thank you Amir for an impeccable review of a so-so product.

 

[Waxx]

It's fine, but it clearly got it's faults, and better is availeble for the money or even less. But it's on a level where it in reality wont matter much. But 1K for this, i'll probally go elsewhere if i was in the market for this kind of amp.

 

[sealman]

From the pics and the website I don't see any cooling holes or anything. Just a solid nice looking case without ventilation
How hot did it run while in testing?.

 

[Multicore]

Looks like too much squeezed into too little of a box.

That's what I was thinking too. A larger box should allow a less messy rear panel and might allow better routing inside to reduce those quirks in the noise. Though in fairness they are practically irrelevant.

 

[jaakkopetteri]

As a compact sized equipment enjoyer, I appreciate them squeezing down stuff even if they have to sacrifice a bit of user friendliness.

 

[sealman]

That's what I was thinking too. A larger box should allow a less messy rear panel and might allow better routing inside to reduce those quirks in the noise. Though in fairness they are practically irrelevant.

If you look at the equivalent Buckeye offering the case is slightly larger (and uglier ) with a lot more room in it.
You lose out on the RCA's and have different adjustable gain points however you gain some ventilation!

 

[Cogito]

The back of that unit is soooo crowded!

 

[ryanmh1]

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.

Exactly. The whole test is something of a muddle because of the test selections, too, in my view. Full output appears to be over 300W into 8 ohms if measured at the traditional 1% THD vs the arbitrary "pick a point on the plot" used for the "tested" figure. At the lowest gain of 11dB the voltage required to drive that output is off the chart. Literally. It's so absurd that it's off the boundaries of my handy reference chart. 10 or 15 volts or more. Most preamps won't drive this to full output at that setting. Even at 16dB gain, it's still crazy high--over 7V from the preamp. Many quality preamps won't even drive that. So why test there? 22dB will be the most common gain level for separates, where 4V is usually available (which is about what would be needed to drive it to full output). But, for a truly fair comparison, one would need to use the 32dB gain setting, which is where *most* amps are fixed at [edit: if they have this much output power]. How it performs with an 11dB or 16dB gain structure is more of a curiosity than anything. Few will even use those gain settings.

Unfortunately, we don't know how it does when set to "normal" mode. It's going to be worse. With an RCA input, it already falls apart. And the distortion in higher frequencies shows a lot of nonlinearities and issues typically of many Class Ds. Audible? I don't know, but I don't like it. Never have. It's just flat out poor performance, albeit remarkably decent... for a Class D. It basically performs on par (via RCA input) just below state of the art in 1978. The only nice thing here is that it weighs very little for the power. That's new, at least. That's what Hypex brought to the table (along with dozens of "manufacturers" all selling the same thing). As for reliability, we'll see. For what Monoprice/ATI are selling US made Monolith amps for these days, I really don't understand the appeal of these things for 2 channel except for the space constrained. And just which space constrained person needs 300/500 watts? "Space constrained" says bookshelf system. With "real" speakers there is probably room for a "real" amplifier that weighs 80 pounds and probably won't break and be unrepairable. I guess I'm just curmudgeonly, even if I'm not old yet...

 

[Paffi]

Regarding the optics, maybe a nice fit to the Wiim Ultra....

 

[Spkrdctr]

After closely examining the interior and exterior of the unit, it was quite plain to see why the RCA performance was so low. It was the obvious lack of tube connectors!!! Everyone knows this....

 

[Zwepp]

I'm not so sure, If we compare:
View attachment 384705
to
View attachment 384706
It's quite clear that there is way more interference for some reason.

So we're talking about a 2-4 dB difference, while if we got these numbers from an AVR it would've been hosanna to the moon and back three times over. It's all so relative and beyond our scope of hearing.

 

[voodooless]

It's all so relative and beyond our scope of hearing.

It surely is, but this is about a fine wrong excellence, not audibility.

 

[Zwepp]

It surely is, but this is about a fine wrong excellence, not audibility.

I understand. From an engineering point of view it could be better, therefore it should be better. Especially sinds it's already been done. On the other hand, how much does it really matter?

 

[pseudoid]

Shoot. If I had known about that model, I would have asked for it!!!

... and you probably would've never returned it back either!
Thank you for the review.

 

[georgehifi]

I started with the lowest gain (Naturally there is some loss when you increase gain)

Amirm hi, seeing there's a bit of difference, do you know if the lowest gain setting bypasses in the input buffer?, as I found it a decent sound quality bonus if it's done and your source still has high enough output voltage to use it for your loudest listening level
Cheers george

 

[Dougey_Jones]

Clearly unfinished product from IOM.
Probably the problem is badly designed input board and /or wiring.
INHO, not worth for the asking price.
Hypex NCx500 in a custom box must be better than this.

Significantly hobbled performance compared to my Apollon NCx500ST which was tested by Amir. Input board has to be bungled for the RCA inputs to perform that badly.

 

[617]

Amazing how good amplifiers have gotten for this kind of money.

 

[restorer-john]

At the lowest gain of 11dB the voltage required to drive that output is off the chart. Literally. It's so absurd that it's off the boundaries of my handy reference chart. 10 or 15 volts or more. Most preamps won't drive this to full output at that setting. Even at 16dB gain, it's still crazy high--over 7V from the preamp. Many quality preamps won't even drive that. So why test there?

Exactly. There's no point whatsoever.

This "low gain to extract the best numbers for an ASR review thing" has gotten completely stupid. As you say, absurd.

Don't take any notice of it, or the results. Demand more representative levels/gains and testing for typical usage scenarios. What's next? Take the 26.7V APX555B analyzer maximum output and do a unity gain, 178W@4R "power amplifier"? That will surely top the charts. I can't wait.

The consumer world of HiFi is not low gain. 99% of it is unbalanced and will remain so for decades to come. Standard levels have been creeping up since CD in 1982, but anything over 2V unbalanced and 4V balanced is not going to be remotely compatible with the vast majority of HiFi made in the past, the present, or the future.