This is a review and detailed measurements of the AIYIMA A70 stereo class D amplifier. It was sent to me by the company and costs US $190 with 48v @ 5 amp supply. As tested with 48v 10amp GaN supply, it costs US $220.
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As you see, the A70 comes in vertical desktop configuration. Controls are easy: push the button for power up and again to cycle between XLR and RCA inputs. Hold it for a few seconds and it goes into standby. Back panel shows nice inclusion of balanced XLR inputs:
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Yes, that 10 amp brick is the mother of all external power supplies!
At 480 watts, any heat dissipation would be challenging given the sealed box. Use of GaN transistors seems to have enabled high efficiency as it hardly warmed up during the testing. The amp's heat source is on the bottom. I wish the feet were taller to allow better convection cooling. Fortunately that area didn't get too hot in testing.
Nice to see trigger input to allow one button power up of the audio chain from the source. We also have a sub output wit variable filter output (yes, it is controlled by the volume setting).
Diagonal speaker terminals help some to fit beefier speaker wire termination.
There is a switch to add 3 dB of gain to RCA input. I didn't realize this until after testing. It is a smart move as the gain otherwise may be a bit low for some people.
The A70 is one of the few TI TPA3255 chip based amplification utilizing post filter feedback loop (PFFB). This should get rid of load dependency and improve linearity by dialing out the distortion from the output stage. Let's see if that is the case.
AIYIMA A70 Amplifier Measurements
Let's start with setting the volume to max using XLR input (all testing with 10 amp supply):
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We see a nice boost in SINAD as predicted, landing the amplifier essentially in our "excellent" category:
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RCA input has fair bit lower performance but still above average:
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Note that I adjusted the volume down to 25 dB per my recent standard of testing amps (used to use 29 dB).
Noise performance is excellent:
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Despite its lower gain with XLR input, you can still reach full power at 3.3 volts which is well below nominal 4 volts we see out of majority of DACs. So I am good with that.
Let's jump into frequency response as that is the other big deal:
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Nice! We see a bit of frequency dependency but it is outside of our hearing range.
I set the subwoofer output frequency to the lowest and measured this:
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I don't know how this is useful for anyone....
Crosstalk is extremely good:
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Good performance numbers give way as you go up in higher frequencies in multitone and especially in 19+20 kHz IMD:
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Let's see how much power we have:
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That's a lot coming out of this little box. We are talking nearly 360 watts total. 8 ohm output is naturally lower:
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Edit: as noted, performance does degrade above certain frequency:
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My reactive load doesn't like these bridged amps. The issue seems to be in one channel so I left that disconnected and drove only one:
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The amplifier is specified down to only 4 ohm but seemed robust enough to even handle 2 ohms, albeit with a good bit of voltage drop. Translating the above into watts we get:
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For those of who want to use these amps in mono, you now have that information as well.
There is likelihood of a turn on "pop" but turn off noise is completely eliminated:
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Finally, amplifier was essentially ready to go on power up:
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Conclusions
What a journey to have watched in these "chip amps." We have gone from $30 to $40 amplifiers with horrible performance to above average in less than $100. Load dependency remained though and so many of us pointing it out, we finally have a solution to that as well. Alas, cost has increased so we are not talking about a fast food meal but one at a nice restaurant. You have to decide now if the extra performance is worth it. It is to me as an amplifier doesn't obsolete so might as well get a good one and sleep easy.
I am happy to recommend the AIYIMA A70 stereo amplifier.
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