This is a review and detailed measurements of the Fosi Audio V3 stereo amplifier. It was sent to me by the company and costs US $89.99 with stock 32 volt supply. Price goes up to $109.99 with the 48 volt supply. There is a $10 discount coupon right now.
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Despite its budget price, the V3 manages to look elegant with the hole pattern on top and large and smooth feeling Volume/On/Off control. Power supply is external and as noted, you get a choice:
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As you will see later, you really want the 48 volt version:
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Yes, it is a larger supply but you are going to hide it behind your desk anyway so might as well live the good life with the increased power there.
The amplifier is based on TI TPA3255 class D amplifier IC. There are replaceable op-amps for those of you who have nothing better to do than mess with the design.
When I took the amplifier out of the package, I noticed something rattling in there. Fearing the worst, I took the unit apart. Turns out one of the two large power supply caps had lost its adhesion to the PCB. The putty used is to keep the cap glued to the PCB was too flexible and had broken loose. No harm though as the cap is laying on its side and can't go anywhere. The sound I was hearing was it moving just a hair up and down and hitting the top of the case. Suggest company use a different material to fix this.
I will post the pictures of the insides later. For now, a large aluminum couples the amplifier IC to the case. There is no thermal grease but the amp ran cool enough that I don't think you need to worry about it. But if you are, this you can remedy yourself. Despite me pushing the amp to max power repeatedly, it just got warm to touch. The protection circuit was the best kind with high tolerance of clipping and audio-restart.
Fosi Audio V3 Amplifier Measurements
I performed the low power tests using the 32 volt supply. The rest is done with both. So let's start with our usual dashboard:
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Distortion is nicely kept to -100 dB so we are noise limited causing SINAD to land around 88 dB. This is well above average for all amplifiers tested:
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Notice how many amplifiers it beats to the right of it!
Noise performance is also quite good for the class, almost clearing the hurdle for 16 bit content at just 5 watts:
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Frequency response shows load dependency which all class D amplifiers in this price range show:
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In English, this means that depending on which speaker you use, the sound may be a bit bright or a bit dull if your hearing extends to 20 kHz. You can counter with EQ (which you better have for good sound in your room).
Multitone and 19+20 kHz show good performance for the class:
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Edit: forgot to post crosstalk measurement:
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Let's see how much power we can get out of this little box into 4 ohm:
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You normally wouldn't expect to get more power with a 48 volt supply compared to 32 volt when their current ratings are the same. But as I noted in the picture at the start, the larger power supply is conservatively rated and is able to pump out more current for peaks. We can see this in our short-term power measurements:
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With 8 ohm volt, we are more in need of voltage so naturally we get tons more there as well with the 48 volt supply:
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Transfer function is quite good for class D and I was especially impressed with its ability to pump out same power at high frequencies as many amplifiers go into protection there:
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There is some pop noise when turning on and off but it is very mild:
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The amplifier is stable on power up:
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Some of you have been aiming at creating more work for me by asking for for efficiency tests. I developed a test that is semi-automatic and provides reasonable accuracy (within 5%):
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Note that part of the heat is dissipated in the power supply and part in the amp. The X axis is power per channel, not total (amp is driven in stereo).
Edit: here are the teardown pictures:
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Conclusions
State of the art DACs run on highly performant silicon that when well implemented, produces the best performance we have seen. We are seeing similar development with these class D IC amplifiers. Noise and distortion is quite low and beats many amplifiers in the market. They bring two drawbacks: external power supplies and load dependencies. If the latter is resolved, these amplifiers would obsolete large segment of the audio market!
The Fosi Audio V3 is well implemented and brings nice looks and design at a bargain price. Company is also quite receptive to customer input and is a delight to work with behind the scenes. I don't know what else we could ask for!
I am going to recommend the Fosi Audio V3 stereo amplifier.
EDIT: a few pages in the thread claim was made that the input buffer opamp must be fake as they don't look like the official TI chip packaging. Company chimed in a couple of days later saying they bought the ICs directly from TI. And showed the purchase order proving the same. It seems the "internet got this wrong" as far as what constitutes a fake as TI is using two different factories with different packaging.
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