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ICEPower 125ASX2 Class D Amplifier Review

amirm

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#1
This is a review and detailed measurements of a DIY amplifier based on ICEPower 125ASX2 module in Ghentaudio case. It is on kind loan from a member. The owner says the total cost is only US $220. I can't find the amp at the price he bought it so maybe it costs a few dollars more but still, it is a good price.

Despite costing only US $90 including wiring, the case is nice:

ICEPower 125ASX2 Class D Switching DIY Audio Amplifier Review.jpg

I like tall feet on amplifiers to allow better cooling although this amp case barely got warm even under power.

The case may be budget priced but the beefy speaker connections are not:

ICEPower 125ASX2 Class D Switching DIY Ghentaudio case Audio Amplifier Review.jpg

The ICEPower 125ASX2 is a stereo amplifier and power supply all in one. So it is quite compact and easy to to put together.

In use, the unit was quite robust, never complaining once. Didn't shut down even well into clipping. This is far better than typical mass consumer AVRs and cheap stereo amplifiers which either go into protection mode or in case of my Sony receiver, outright kill themselves. Combine this with a DAC with volume control and you are Golden.

Amplifier Audio Measurements
As usual we start with our dashboard:
ICEPower 125 watt stereo class D amplifier Audio Measurements.png


The gain of 25 is a tad on the low side but I was able to get it to clip at around 1.4 volts. So any modern DAC with 2 volt maximum output should do fine.

I had to ground my floating RCA output on the analyzer to reduce the excessive mains leakage/noise at 60 Hz.

I wish both channels were the same but they are not, with one having 5 dB worse performance. Averaging the two still puts the 125ASX2 above average of all amplifiers tested:

Best Class D stereo amplifier DIY.png


Frequency response was flat into my resistive load:
ICEPower 125 watt stereo class D amplifier Frequency Response Audio Measurements.png


Datasheet says bandwidth is 130 kHz but I am shy of that at 80 kHz. Still, this is quite good.

There is a tiny bit of ringing due to output filter which may get worse with real speaker loads.

Crosstalk is good, besting our $25 amplifier (in red) but staying far of our reference Benchmark amplifier:

ICEPower 125 watt stereo class D amplifier Crosstalk Audio Measurements.png


Dynamic range is good as well:
ICEPower 125 watt stereo class D amplifier SNR Audio Measurements.png


32-tone test resembling "music" shows rapidly rising distortion at higher frequencies:
ICEPower 125 watt stereo class D amplifier Multitone Audio Measurements.png


Threshold of hearing also increases with frequency above 5 kHz so the graph is worse on the eye than the ear.

Power into 4 ohm gives us:

ICEPower 125 watt stereo class D amplifier Power into 4 Ohm Audio Measurements.png


Definitely not reference quality but also much better than our premium AVR (NAD). Noise floor is much lower but distortion starts to take over at just 2 watts or so. Fortunately it remains below 80 dB prior to clipping, giving us 96 watts. Using a 0.1% criteria for THD+N we get this versus frequency:


ICEPower 125 watt stereo class D amplifier Regulated Power 4 Ohm Audio Measurements.png


At 40 Hz (the highest amplitude in samples of music in my library) we achieve 111 watts. At 20 kHz though, due we fall flat to just 1 watt due to either noise or distortion. Note that this noise/distortion is ultrasonic so not an audible concern per se.

At 8 ohm power naturally drops:
ICEPower 125ASX2 stereo class D amplifier Regulated Power 8 Ohm Audio Measurements.png


But once again we beat the NAD AVR.

Spectrum of the amplifier at 5 and max power shows the usual switching noise but at lower amplitude than some:
ICEPower 125ASX2 watt stereo class D amplifier FFT Spectrum Switching Frequency Audio Measurem...png


I have seen switching amps that have only 20 dB or so attenuation of switching noise so this is an improvement.

Our tests have been at 1 kHz so let's see what happens at other frequencies:

ICEPower 125 watt stereo class D amplifier THD+N vs Frequency vs Level Audio Measurements.png


As noted earlier, distortion rises good bit at higher frequencies (top graphs).

Thermal Stability
I ran the amp at 5 watts and monitored its noise and distortion:

ICEPower 125 watt stereo class D amplifier Warm up Measurements.png


As you see, performance continued to degrade and did not converge. I got bored and started the test you saw earlier. So best to keep the unit in a freezer for best performance and stay away from my old home town, state of Florida. :D

That one glitch is a puzzle and something I see in amplifiers as I test them. May be due to cabling. I played with the cables and got that much smaller glitch that follows it.

On the right is the same THD+N but shown as parts per million to show that we are talking about small numbers.

Conclusions
The bottom of the amplifier market is comprised of single IC amplifiers. This class of products uses a full module with much elevated performance level. It is great to have a super efficient, cool and light amplifier that runs circles around the amplifier in mass market AVRs for not a lot of money.

Overall, I am happy to recommend the ICEPower ASX125 as a budget amplifier build.

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

Was driving home today after picking up another amplifier for review. Put one of the panthers in the passenger seat so that I could use the carpool lane. Well, got pulled over by the police and was handed a $320 ticket. Apparently animals don't count. While some of this story is not true, other aspects of it are, leading me to feel poor and depressed. Appreciate healthy donations as a remedy using: https://www.audiosciencereview.com/forum/index.php?threads/how-to-support-audio-science-review.8150/
 

SDC

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#2
Maybe the unit is cheap 125asx2 from aliexpress? Then the price is 115$ so 90$ case + shipping is 220$.

I've used 50asx2 from aliexpress, don't know whether it's fake or b-stock but worked without hiss and drove 2544r00 fine without protection caps and L-pads
 

bunkbail

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#5
Are you serious? IMO, this is a horrible amplifier.

View attachment 42879

View attachment 42880
Agreed, it's horrendous. You can get far better performance at ~$200, for example LJM L12-2 power amp, 120W @ 8 ohm, 200W @ 4 ohm (THD 0.0005% 1kHz at 10W). I own a unit and it sounded absolutely glorious with my Wharfedale EVO 4.2 speakers (I'm totally not biased btw).
 

Arnandsway

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#6
Because of the higher distortion in the high frequencies, I think the best use case for this amp would be to amp woofers in a 2 or 3-way, bi-amped system.
 
OP
amirm

amirm

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Thread Starter #7
Are you serious? IMO, this is a horrible amplifier.
I am serious and no, it is not. Most of us can't even hear 20 kHz let alone its harmonic distortion that is included in those graphs.
 

Juhazi

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#8
We must remember that ICEpower ASX series was one of the first modules, designed more than ten years ago. Still going strong. I have had two 125+50 modules driving 4-way speakers for six years now - no problems and power on 24/7.
 
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JohnYang1997

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#11
Does it have chassis and power supply? If not I can make one that has 0.0003%.
 

Koeitje

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#12
I am serious and no, it is not. Most of us can't even hear 20 kHz let alone its harmonic distortion that is included in those graphs.
Doesn't it take a massive dive in power after 8khz? I can see this work as an amplifier for a midwoofer in a powered system, but not for driving tweeters.
 

Tks

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#13
Alright, the AHB2 from Benchmark was shown off, when? Like 2013 or somewhere thereabouts?

On the market a year or two later I suppose? Anywho, it's been half a decade. And I know the device is quite costly. But I just can't understand how it's been THIS LONG, and after all these years, even devices near it's price point, aren't actually "that close".

>_>
 

bunkbail

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#15

VintageFlanker

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#16
http://vi.raptor.ebaydesc.com/ws/eB...0&pm=1&ds=0&t=1571128951000&ver=0&cspheader=1

This is the one that I bought, it has some graphs, including THD+N vs freq. Looks good to me, but still need some verification from people who own the latest analyzers.
https://rover.ebay.com/rover/0/0/0?mpre=https://www.ebay.com/ulk/itm/123223488897

Looks promising. About 300€ shipped, for such specs and volume control...o_O Would be glad to see this checked/measured by @amirm!
 

Koeitje

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#17

pma

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#18
Doesn't it take a massive dive in power after 8khz? I can see this work as an amplifier for a midwoofer in a powered system, but not for driving tweeters.
Yes, and non-linearity issues at higher frequencies almost always are transformed into lower frequencies as well, as intermodulations or another issues, as I have shown yesterday
https://www.audiosciencereview.com/...ax-396-integrated-amplifier.10410/post-287384

To prevent the higher frequency issues and intermodulations to lower frequencies one would need to cut input signal somewhere at 5kHz for this ICE "amplifier".
 

Juhazi

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#19
"a massive dive in power after 8khz? "

Hey, that's just the power vs. distortion curve! For sure it can drive tweeters fine, even with high signal level that happen only with measurement sweeps.
 
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#20
"a massive dive in power after 8khz? "

Hey, that's just the power vs. distortion curve! For sure can drive tweeters fine, even with high signal level that happen only with measurement sweeps.
Indeed. I am curious why people want to see this curve for anything but a subwoofer amp, as it does lead some to think the amp is no good :) I would prefer to see what output power it can manage across the full 20 to 20k audio bandwidth and still maintain that same 0.1% distortion.
 
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