This is a review and detailed measurements of Onkyo M-282 Power (speaker) amplifier. It is on kind loan from a member who bought it a few years ago but had not used it. Seems like it was just discontinued as I checked the price yesterday and it was being sold for $300 or so from Amazon. The suggested replacement by Amazon is lower power (75 versus 100 watts for M-282) but is also cheaper at $210.
The box is quite large but other than the left side that is weighted down by a transformer, it feels rather light:
The front looks slick and high quality.
The back has two pairs of RCA connectors: one for input and one for output. There is a switch to select auto-on with audio, 12 volt trigger, or always on which is the mode i used.
There is trim potentiometer in the back to set the input sensitivity. At first I left this in the default middle setting but that showed fair amount of channel mistmatch. So I set it to max and the two equalled out.
There is a delayed on which I assume also includes a protection circuit.
The unit is rated down to 6 ohm I think but she had no problem handling my 4 ohm load for testing.
Let's get into measurements and see how it performs.
Measurements
Unlike previous amplifiers I have tested, this is a traditional class AB amplifier meaning it is much less efficient. This point was amply made during my warm-up exercise with copious amount of heat oozing out of its relatively small internal heat sink. I was only using 20 watts/channel but with less than 50% efficiency, the thing was likely generating 50+ watts of heat. Here is how the distortion rated during that time:
Pretty odd in that the more distorted channel (blue) got fair bit better as it warmed up but the other did not change much.
The infrared thermal image shows that the thing was cooking and cooking good:
The cursor indicating 71 degrees C is on the heatsink that holds the power devices for the amplifier. They are using a heatsink with very large fins which is good but there is just no mass to it. It is not connected in any substantial way to the chassis so relies on ample convection from the bottom through the top vents. Better give this amp plenty of room to breath.
Given the much elevated temps, I did not dare to run it for 5 minutes at full power. I did however sweep the input level to see how she could do in shorter period:
We are getting 110 watts which is just a hair over the rated 100 watts but that is at 8 ohm and my test is with 4 ohm. So not much headroom here with lower impedances due to shortfall of the power supply current.
Compared to the other two switching amplifiers, the Crown XLS 1502 (brown) is more noisy than it but has much lower distortion and has far more output power. The Hypex ncore (blue) beats it on all fronts but is also four times more expensive.
SIgnal to noise ratio is good and matches the spec from what I recall at 110 dB:
Frequency response is essentially perfect since class AB amplifiers don't need the output filters that switching amps have:
Likewise ultrasonic spectrum above 20 Khz is clean (sans the harmonic distortion of the amplifier):
Distortion+noise was very revealing of the amplification issues with respect to topology:
Notice how the distortion climbs on the switching Crown XLS 1502 above 1 kHz or so. The more power they produce (dashed lines), the more distortion climbs.
The class AB Onkyo M-282 had the opposite response. At lower levels of 1 and 5 watts, its distortion and noise was clearly better than Crown especially as frequencies rose.
Once pushed to tune of 150 watts, the Onkyo distortion rises up across the board which is not surprising. But look at the huge rise in distortion as source frequencies got lower than 50 Hz. The inadequate power supply has more of a problem with long cycles of low frequencies.
Both of these show evidence of what I subjectively hear when testing amplifiers with speakers: class AB amplifiers run out of steam in low frequencies first. Play something with heavy drums and gradually increase the level and pay attention to bass to see if the "thumps" get anemic.
In contrast, with class D/switching amplifiers, I find that they are exceptionally good at bass so the above test doesn't work. Instead, focus on clarity of high frequencies as you increase levels. Use content that has isolated high notes to make this easier.
Conclusions
I am torn when evaluating such equipment. On one hand I am astonished that a brand name power amplifier using class AB can be made, shipped and sold for so little money. The economics of this are mind boggling. I suspect these companies lose money on these low-end products and try to make it up with higher tier products.
On the other hand, this is not the type of performance I like to see in my system. We are so far, far away from level of distortion of our digital sources to the tune of 30+ dB. Designers often work hard to improve a system by 3 dB and here we have such a massive shotfal. As such, I can't recommend this amplifier unless funds are very low.
As we test more of these amplifiers we should get a better idea of what is out there that is a great find.
-------------
As always, questions, comments, recommendations, etc. are welcome.
They say you should save money for a rainy day. It rains for about 6 months here so I need plenty of that!!! Please consider donating funds using:
Patreon: https://www.patreon.com/audiosciencereview), or
upgrading your membership here though Paypal (https://audiosciencereview.com/foru...eview-and-measurements.2164/page-3#post-59054).
The box is quite large but other than the left side that is weighted down by a transformer, it feels rather light:
The front looks slick and high quality.
The back has two pairs of RCA connectors: one for input and one for output. There is a switch to select auto-on with audio, 12 volt trigger, or always on which is the mode i used.
There is trim potentiometer in the back to set the input sensitivity. At first I left this in the default middle setting but that showed fair amount of channel mistmatch. So I set it to max and the two equalled out.
There is a delayed on which I assume also includes a protection circuit.
The unit is rated down to 6 ohm I think but she had no problem handling my 4 ohm load for testing.
Let's get into measurements and see how it performs.
Measurements
Unlike previous amplifiers I have tested, this is a traditional class AB amplifier meaning it is much less efficient. This point was amply made during my warm-up exercise with copious amount of heat oozing out of its relatively small internal heat sink. I was only using 20 watts/channel but with less than 50% efficiency, the thing was likely generating 50+ watts of heat. Here is how the distortion rated during that time:
Pretty odd in that the more distorted channel (blue) got fair bit better as it warmed up but the other did not change much.
The infrared thermal image shows that the thing was cooking and cooking good:
The cursor indicating 71 degrees C is on the heatsink that holds the power devices for the amplifier. They are using a heatsink with very large fins which is good but there is just no mass to it. It is not connected in any substantial way to the chassis so relies on ample convection from the bottom through the top vents. Better give this amp plenty of room to breath.
Given the much elevated temps, I did not dare to run it for 5 minutes at full power. I did however sweep the input level to see how she could do in shorter period:
We are getting 110 watts which is just a hair over the rated 100 watts but that is at 8 ohm and my test is with 4 ohm. So not much headroom here with lower impedances due to shortfall of the power supply current.
Compared to the other two switching amplifiers, the Crown XLS 1502 (brown) is more noisy than it but has much lower distortion and has far more output power. The Hypex ncore (blue) beats it on all fronts but is also four times more expensive.
SIgnal to noise ratio is good and matches the spec from what I recall at 110 dB:
Frequency response is essentially perfect since class AB amplifiers don't need the output filters that switching amps have:
Likewise ultrasonic spectrum above 20 Khz is clean (sans the harmonic distortion of the amplifier):
Distortion+noise was very revealing of the amplification issues with respect to topology:
Notice how the distortion climbs on the switching Crown XLS 1502 above 1 kHz or so. The more power they produce (dashed lines), the more distortion climbs.
The class AB Onkyo M-282 had the opposite response. At lower levels of 1 and 5 watts, its distortion and noise was clearly better than Crown especially as frequencies rose.
Once pushed to tune of 150 watts, the Onkyo distortion rises up across the board which is not surprising. But look at the huge rise in distortion as source frequencies got lower than 50 Hz. The inadequate power supply has more of a problem with long cycles of low frequencies.
Both of these show evidence of what I subjectively hear when testing amplifiers with speakers: class AB amplifiers run out of steam in low frequencies first. Play something with heavy drums and gradually increase the level and pay attention to bass to see if the "thumps" get anemic.
In contrast, with class D/switching amplifiers, I find that they are exceptionally good at bass so the above test doesn't work. Instead, focus on clarity of high frequencies as you increase levels. Use content that has isolated high notes to make this easier.
Conclusions
I am torn when evaluating such equipment. On one hand I am astonished that a brand name power amplifier using class AB can be made, shipped and sold for so little money. The economics of this are mind boggling. I suspect these companies lose money on these low-end products and try to make it up with higher tier products.
On the other hand, this is not the type of performance I like to see in my system. We are so far, far away from level of distortion of our digital sources to the tune of 30+ dB. Designers often work hard to improve a system by 3 dB and here we have such a massive shotfal. As such, I can't recommend this amplifier unless funds are very low.
As we test more of these amplifiers we should get a better idea of what is out there that is a great find.
-------------
As always, questions, comments, recommendations, etc. are welcome.
They say you should save money for a rainy day. It rains for about 6 months here so I need plenty of that!!! Please consider donating funds using:
Patreon: https://www.patreon.com/audiosciencereview), or
upgrading your membership here though Paypal (https://audiosciencereview.com/foru...eview-and-measurements.2164/page-3#post-59054).