This is a review and detailed measurements of the AIYIMA A70 Mono TI TPA3255 based class D amplifier. It was sent to me by the company and is on sale for US $116.
The on/off and input type selectors have good quality feel to them as do the rotary controls. Right one is volume but left one had my scratching my head. Subwoofer frequency? That is something you set once so you don't need front adjustment. Even if you did, what is one in the back that has the same name?
As is, measurements showed that neither made a difference in frequency response of the speaker output. If you however toggle a switch underneath, the front control at least becomes active, setting the high frequency roll off. I could not figure out what the back control did. Reading the instructions didn't help but my conclusion was that the switch turns the amplifier into one that drives passive subwoofer (woofer and no amp). Passive subs have fallen out of favor in US at least for more than two decades. You can get ultra low cost subs that are active. AIYIMA has seemed to gone to great lengths to implement such a functionality with dedicated front and back controls. It is quite puzzling to me. Hopefully you all didn't talk them into this!
Nice to see trigger input so amp can be woken up by the source having the same output. And inclusion of extra gain for RCA solves the battle of what the gain should be by default. I like the default of it being off. But some want higher gain (which brings with it more noise and potentially channel imbalance).
I forgot to take a picture of the power supply but it is GaN based, 48 volt @ 5 amp for total of 240 watts in a relatively compact package. In use neither the power supply, or the case (top or bottom) warmed up let alone get hot. Either thermal management is very good or hot stuff inside care isolated from the case.
Note that there is another AIYIMA A70 amplifier (without mono). As with that unit, the mono version here implements post-filter feedback (PFFB) so should have high level of isolation from load/speaker dependency compared to units without. We will measure this.
AIYIMA A70 Mono Measurements
Let's start with XLR input at max volume:
Distortion is at inaudible -110 dB so noise dominates SINAD at 94 dB, placing the A70 mono at the top of the "competent" group of amplifier we have tested:
RCA input is similar despite higher gain:
I am happy to see 25 dB gain here as that is what I think companies need to target unless max power is not reached with 2 volt input.
Frequency response test shows that PFFB is working, sans a bit of increased output impedance:
Given that the 4 ohm also peaks at 20 kHz, the 8 ohm peak is now 1 dB higher than mid frequencies which may be audible to some young people.
SNR is excellent and matches spec fully:
I was surprised by the increasing intermodulation distortion in low frequencies in multitone test:
It is not something I have seen in other implementations. Fortunately our hearing threshold is pretty high at lower frequencies so likely not audible. The rise in the same at higher frequencies is typical:
Let's measure available power:
Sweeping at different frequencies we see the jump in distortion at lower end of the spectrum (20 Hz):
On positive front the curves are much smoother and don't rise as much as some other implementations.
Power is nicely maintained across full audible spectrum (with a degree of error):
I went to test the amp with my Loadbox reactive load but sadly, found the load box not communicating with the PC anymore.
Here is the impressive warm up performance:
I didn't take a thermal image because as I noted in the intro, the amp and its supply were at room temperature more or less.
Conclusions
AIYIMA A70 MONO amplifier brings highly competent performance to the table with performance that beats majority of amplifiers I have tested. Yet it costs so little. Having balanced input, selectable gain for RCA and trigger are much appreciated. I am at a loss as to what the subwoofer features are about but fortunately, they are disabled using a switch. To be clear, what we/I want is to roll off the main output and have an unmodified output for sub. The sub will have its own filtering. It is the mains that needs filtering.
I am going to recommend the AIYIMA A70 Mono 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/
The on/off and input type selectors have good quality feel to them as do the rotary controls. Right one is volume but left one had my scratching my head. Subwoofer frequency? That is something you set once so you don't need front adjustment. Even if you did, what is one in the back that has the same name?
As is, measurements showed that neither made a difference in frequency response of the speaker output. If you however toggle a switch underneath, the front control at least becomes active, setting the high frequency roll off. I could not figure out what the back control did. Reading the instructions didn't help but my conclusion was that the switch turns the amplifier into one that drives passive subwoofer (woofer and no amp). Passive subs have fallen out of favor in US at least for more than two decades. You can get ultra low cost subs that are active. AIYIMA has seemed to gone to great lengths to implement such a functionality with dedicated front and back controls. It is quite puzzling to me. Hopefully you all didn't talk them into this!
Nice to see trigger input so amp can be woken up by the source having the same output. And inclusion of extra gain for RCA solves the battle of what the gain should be by default. I like the default of it being off. But some want higher gain (which brings with it more noise and potentially channel imbalance).
I forgot to take a picture of the power supply but it is GaN based, 48 volt @ 5 amp for total of 240 watts in a relatively compact package. In use neither the power supply, or the case (top or bottom) warmed up let alone get hot. Either thermal management is very good or hot stuff inside care isolated from the case.
Note that there is another AIYIMA A70 amplifier (without mono). As with that unit, the mono version here implements post-filter feedback (PFFB) so should have high level of isolation from load/speaker dependency compared to units without. We will measure this.
AIYIMA A70 Mono Measurements
Let's start with XLR input at max volume:
Distortion is at inaudible -110 dB so noise dominates SINAD at 94 dB, placing the A70 mono at the top of the "competent" group of amplifier we have tested:
RCA input is similar despite higher gain:
I am happy to see 25 dB gain here as that is what I think companies need to target unless max power is not reached with 2 volt input.
Frequency response test shows that PFFB is working, sans a bit of increased output impedance:
Given that the 4 ohm also peaks at 20 kHz, the 8 ohm peak is now 1 dB higher than mid frequencies which may be audible to some young people.
SNR is excellent and matches spec fully:
I was surprised by the increasing intermodulation distortion in low frequencies in multitone test:
It is not something I have seen in other implementations. Fortunately our hearing threshold is pretty high at lower frequencies so likely not audible. The rise in the same at higher frequencies is typical:
Let's measure available power:
Sweeping at different frequencies we see the jump in distortion at lower end of the spectrum (20 Hz):
On positive front the curves are much smoother and don't rise as much as some other implementations.
Power is nicely maintained across full audible spectrum (with a degree of error):
I went to test the amp with my Loadbox reactive load but sadly, found the load box not communicating with the PC anymore.
Here is the impressive warm up performance:
I didn't take a thermal image because as I noted in the intro, the amp and its supply were at room temperature more or less.
Conclusions
AIYIMA A70 MONO amplifier brings highly competent performance to the table with performance that beats majority of amplifiers I have tested. Yet it costs so little. Having balanced input, selectable gain for RCA and trigger are much appreciated. I am at a loss as to what the subwoofer features are about but fortunately, they are disabled using a switch. To be clear, what we/I want is to roll off the main output and have an unmodified output for sub. The sub will have its own filtering. It is the mains that needs filtering.
I am going to recommend the AIYIMA A70 Mono 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/
