Measurement & Review of the AIMIYA A07 Power Amplifier

A few months ago I purchased the AIMIYA A07 Power Amplifier from Amazon for a whopping $60 during Prime Day. I’ve had the unit hooked up to my simple studio setup and have been very impressed with it so far. The performance-to-cost ratio is pretty remarkable. It’s worked flawlessly over the past months and I have been very happy with it. I currently have it hooked up to my modded Jamo’s and it sounds absolutely amazing. It has plenty of volume and never seems to run out of power. So today I finally decided to pull out my measurement gear and so I could get some real data on its performance, to see just what this amp is capable of. I know there are plenty of other reviews out there for this amp, part of the reason I purchased it in the first place, so I don’t think I’ll be sharing anything earth shatteringly new. But I enjoyed putting this thing on the bench and getting some data of my own just the same. So read on to see how she performs!

The heart of the AIMIYA A07 is a TI TPA3255 High-power Class D chip amplifier. The datasheet for this part can be found here This is a very popular chip amp and has made its way into many small home audio amplifiers from a variety of manufacturers. However, worth noting is implementation of this chip is still up to the designer and AIMIYA is no slouch in this realm touting a long line of amplifier options to suit almost anyone’s need. Overall output power is dictated mostly by how much raw DC power you can provide. AIMIYA supplies a very respectable 32V/5A power supply with the unit which for most people will be plenty, as I’ll show here. But note that that amplifier has more to give, if you’re willing to spend a little more for a larger, more powerful DC power supply. And based on the measurements I took with the stock power supply, I believe more power available in the TPA3255.

So a quick re-cap of my measurement setup (which take it for what it’s worth) is based on a simple loop-back measurement using REW, a PreSonous Firestudio audio interface and a custom balanced amp-level to line-level converter/load box that I designed and built for this exact purpose. I’ve played with this setup quite a bit and have basically got it dialed in as best as I can to take as accurate as possible frequency response and distortion measurements of amps that range from 10W to 400W watts. The Firestudio interface is calibrated (via soundcard cal) and is able to provide an overall THD of only 0.00074% and a THD+N of about 0.0063%. While probably not great for measuring high-performance DACs or headphone amps, this setup is fine for measuring most power amplifiers, or at least most of the amplifiers that I’ve come across, as their distortion levels are almost always much worse that this. I’ve included plots of the baseline loopback measurement of just my setup so you can get an idea of where the noise limitations exist. From this you can see that all of the amplifier measurements are higher than the baseline and are therefore going to be fairly representative of truth for this amp. Not to mention nothing I measured drastically contradicts anything already out there already showing what this amp can do.

So first let’s just look at the frequency response of the A07. One of the easiest things to measure, since REW was basically designed to measure frequency response of just about anything. I limited my measurement to 5-22,000 Hz which shows a very nice and flat response from 20-20,000 Hz where the response is down only -0.3 dB at 20 Hz and down -0.8 dB at 20 kHz. This was measured into a 4 ohm load. I did not do any measurements into an 8 ohm load, as I figured most speakers people are going to use with this amp are going to fall into the 4 ohm territory. Including the Jamo’s that I am current using with it. Basically you can assume the total available power will be lower, and the frequency response will peak slightly before cutoff, but it should be minimal. Overall this frequency response is excellent for a Class D amp and represents a decent filter design by the folks at AIYIMA. Take note that the response does start to roll off at around 5 kHz which when combined with a speaker that if normally sounds a bit bright, this roll-off will mellow it out just a bit, but not much, and will likely go unnoticed. The roll-off in the bass response when combined with the type of speakers that most people will use with this amp (ie, small bookshelf speakers) should also go basically unnoticed. That being said, I’d say this amp is about as neutral as you’d expect and should sound great with a majority of speakers.

I only ran one frequency response sweep of the distortion, so what you see for distortion across frequency is just at 5W into 4 ohms. Distortion is respectable at this volume and should be lower than just about any speaker you connect it to. The rest of the power and distortion measurements were done using the RTA Analyzer option within REW. All measurements were done at 1 kHz, with a 256k FFT length and 4 averages. These settings provide a reasonable noise floor balanced against the time to take each measurement, which ended up being about 8 seconds. I have a True RMS voltmeter measuring the voltage directly across the a 100W load resistor. I then calculated the power using Ohms Law P=E^2/R. For simplicity in the setup, while both outputs can be loaded with the 4-ohm load resistor at the same time, I can only measure the loopback through one channel at a time. All of these measurements were done using the left channel, however, I have no reason to suppose the right channel’s performance is very different. I do provide power and distortion curves however for both channels loaded vs. only one channel loaded. As you can see, there is not much difference in performance given the stock power supply.

So to summarize the power response of the A07, this amplifier provides a very respectable 87 watts RMS per channel, both channels driven, into 4 ohms at 0.022% THD and 0.031% THD+N. This exceeds AIYIMA’s max specified output power by 7 watts when using a 32V/5A DC power supply. At 88 watts, the protection circuit kicked in preventing me from driving the amp to 0.1% distortion, let alone 1% distortion where some amps are tested at. I suspect the protect circuit kicked in due to maybe an under-voltage condition caused by the power supply, since the amplifier itself, based on the distortion at this level, showed no signs of stress and was ready to keep going. With only one channel driven, I pushed the amp to 100W where the distortion finally turned the corner and climbed to 0.37%. I did not push the amp beyond this point as this appeared to be where the knee occurs for distortion vs. power and anything more we know the distortion would have climbed drastically, typical of any amplifier power curve. This is all very good though, from an amplifier that so small and so inexpensive, it exceeded my expectations and performed flawlessly in every test. Even the protection circuit kicking in shows that this amp can be pushed to its limit before shutting down, and is able to keep the distortion very low all the while.

So that’s about what you can expect from the AIMIYA A07 Power Amplifier. A solid frequency response and over 80×2 watts RMS into 4 ohms at around 0.031% distortion. The amp is nice and tidy, the volume knob feels nice, the all-aluminum housing feels solid and simple red LED and toggle switch are basically all that adorn the front panel. Standard banana posts for the speaker terminals with both RCA and 3.5mm input jacks making hooking up this amp a breeze. The lack of tone controls, good power, flat frequency response and low distortion, make this a real budget audiophile special that just about anyone can find a good use for in their stereo.

Setup Pics

Measurement Data

About Dan

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