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:
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:
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:
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:
Frequency response was flat into my resistive load:
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:
Dynamic range is good as well:
32-tone test resembling "music" shows rapidly rising distortion at higher frequencies:
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:
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:
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:
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:
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:
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:
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.
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/
Despite costing only US $90 including wiring, the case is nice:
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:
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:
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:
Frequency response was flat into my resistive load:
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:
Dynamic range is good as well:
32-tone test resembling "music" shows rapidly rising distortion at higher frequencies:
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:
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:
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:
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:
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:
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:
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.
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/
