A member asked me a while ago to test the ultra cheap ($18)
UWAYKEY Mini Bluetooth Amplifier on Amazon. To make the clickbait title work
, I omitted the cost of the external power supply you need to bring yourself. What you get is a three board assembly:
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It took less than 5 minutes to put the heatsink on the main class D amp chip and sandwich the main board with the top and bottom. The chip used must be for smart speakers as it has voice prompts when you change inputs. Speaking of that, it has Bluetooth (which I did not test), analog and USB in. The little heatsink has no air flow and in testing, it got quite hot to touch at times.
For testing, I used my lab power supply and set the output voltage to 24 volts (max spec). The supply has 3 Amps max current. Amplifier is rated for dual 50 watts at that voltage input.
UWAYKEY Mini Bluetooth Amplifier Measurements
I started testing with analog input with volume adjusted for 29 dB gain:
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Considering the price, this is not half bad:
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I kludged up a USB type A to type A cable and ran the dashboard test again:
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As you see performance is not as good as analog input. Worse yet, just a few seconds later, it lost stability and would no longer work reliably. If I powered it down, it would work for a second or two and then go crazy again. It may be a design issue or my setup. Either way, I could only continue with analog input testing.
Noise floor is high as you can see in the FFT graphs above:
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Crosstalk managed to be worse than the worst I have tested so far:
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Multitone shows increased distortion at both ends of the spectrum:
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The most important test for class D amps shows strong load dependency:
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So the tonality you get will depend on speaker you hook up to it.
As usual, we fall way short of stated power levels:
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8 Ohm performance was a bit better:
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Response vs frequency is smooth but that may be due to high noise floor which masks distortion:
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Amplifier Listening Tests
I hooked up one channel to my
Infinity Reference 253 speaker and starting to listen. There was a lot more power than I expectedly, likely due to only having to drive one channel. The sound was surprisingly good until you cranked it to max volume. Speaking of which, if I paused input, the last 25% of the volume range produced tweeter hiss that was audible to about 1 meter/3 feet.
I was very satisfied with subjective performance until I landed on two clips, both of which were busy with both bass and treble notes. On these two tracks, the sound was very distorted at almost all volume levels. High frequencies would get gritty and distorted and bass response was bad as well. I power cycled the unit and let it cool and it seemed to play well for a couple of seconds and then would get distorted. It may be that the crest factor is too low causing the amp to drive hard most of the time with these two tracks. And then it overheats and distorts.
Conclusions
The first amplifier I ever built (with my brother when we were 10 or 11 years old) was this massive board and produced only 10 watts a channel. It also cost us many months of allowance. Compare that to this amplifier which for the price of a fast food meal for two, gives you stereo sound that most of the time is impressively good. If it did not distort on those two channels, I would say you could build an amp with two of them and be in business.
Given the distortion/heat issue, I can't recommend the UWAYKEY amplifier.
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