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Fosi Audio V3 Amplifier Review

Rate this amplifier:

  • 1. Poor (headless panther)

    Votes: 11 2.5%
  • 2. Not terrible (postman panther)

    Votes: 37 8.5%
  • 3. Fine (happy panther)

    Votes: 213 49.0%
  • 4. Great (golfing panther)

    Votes: 174 40.0%

  • Total voters
    435

amirm

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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.
Fosi Audio V3 stereo amplifier budget review.jpg

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:

Fosi Audio V3 stereo amplifier budget back panel 32 volt power supply review.jpg

As you will see later, you really want the 48 volt version:
Fosi Audio V3 stereo amplifier budget back panel 48 volt power supply review.jpg


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:
Fosi Audio V3 stereo amplifier budget measurement.png


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:
Best budget stereo amplifier review 2023.png


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:

Fosi Audio V3 stereo amplifier budget SNR measurement.png


Frequency response shows load dependency which all class D amplifiers in this price range show:
Fosi Audio V3 stereo amplifier budget Frequency Response measurement.png

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:
Fosi Audio V3 stereo amplifier budget Multitone measurement.png

Fosi Audio V3 stereo amplifier budget 19 20 kHz measurement.png


Edit: forgot to post crosstalk measurement:
Fosi Audio V3 stereo amplifier budget Crosstalk measurement.png


Let's see how much power we can get out of this little box into 4 ohm:
Fosi Audio V3 stereo amplifier budget Power 4 ohm measurement.png

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:
Fosi Audio V3 stereo amplifier budget Max and Peak 48 volt Power 4 ohm measurement.png


Fosi Audio V3 stereo amplifier budget Max and Peak 32 volt Power 4 ohm measurement.png


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:
Fosi Audio V3 stereo amplifier budget Power 8 ohm measurement.png


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:

Fosi Audio V3 stereo amplifier budget Power 4 ohm vs frequency measurement.png


There is some pop noise when turning on and off but it is very mild:
Fosi Audio V3 stereo amplifier budget Pop on off measurement.png


The amplifier is stable on power up:
Fosi Audio V3 stereo amplifier budget warm up measurement.png


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%):

Fosi Audio V3 stereo amplifier budget Power Efficiency measurement.png


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:
Fosi Audio V3 stereo amplifier budget teardown Top PCB.jpg


Fosi Audio V3 stereo amplifier budget teardown bottom PCB heatsink.jpg

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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amirm

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amirm

amirm

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89w for $120 or so? hard to fathom
It is actually only $100 with the discount. Normal price is $110. Incredible value indeed.
 

Talisman

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Thank you very much Amir, I was looking forward to this review, a lot of hype has been created around this product, and Fosi's promises have unfortunately been only half kept.
Good noise and distortion, but still too much load dependence to talk about high fidelity. Aside from a few sinad points, the BT20a pro also performs a bit better in terms of load dependence.
The specifications advertised by the company of 20/20k +/- 0.1 db are not absolutely respected. What I expected was to get close to the performance of the pa5 topping, but we're not there.
I rationally realize that for a 100 euro product the performance is still excellent, but I had the illusion that they had worked a miracle.
A little disappointed (I say this as an owner)
 

TonyJZX

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here's the BT20

its about the same, a little more power, bit more amenities

i didnt think it would come close to even a $300 amp but to me a lot of this is academic because you may not be able to ABX a difference in real life
 

Jos

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amazing!
I would use it for my backchannels and try to turn it on via a wireless connection when I turn my main amplifier on....
Does it automatically turn the amp on when an input signal is becoming available?
For this reason I would really like to know what standby power consumption is measured.....
thx for your reply in advance!
 

potfur

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Thank you very much Amir, I was looking forward to this review, a lot of hype has been created around this product, and Fosi's promises have unfortunately been only half kept.
Good noise and distortion, but still too much load dependence to talk about high fidelity. Aside from a few sinad points, the BT20a pro also performs a bit better in terms of load dependence.
The specifications advertised by the company of 20/20k +/- 0.1 db are not absolutely respected. What I expected was to get close to the performance of the pa5 topping, but we're not there.
I rationally realize that for a 100 euro product the performance is still excellent, but I had the illusion that they had worked a miracle.
A little disappointed (I say this as an owner)
There appear to be two sets of specs stated on two Fosi sites (fosiaudioshop and fosiaudio). The frequency response spec on the fosiaudioshop website is as follows (which appears to tally with Amir's measurements). The rest of specs also look realistic, apart from the maximum power output of course, which they copy from the chip manufacturer, and which is WILDLY optimistic (300 W x 2 @ 4 ohm).
1687256714813.png


A better (unrealistic) frequency response is stated on the fosiaudio website:
1687256996225.png

I attach the two full sets of specs for comparison below:
1687257052973.png


1687257062058.png
 

Jeromeof

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If the latter is resolved, these amplifiers would obsolete large segment of the audio market!
Thanks again for an amazing review - I imagine they are squeezing the last bit of performance from the TPA3255.

So I know nothing about op-amp's but would it be possible to find an op-amp that helps the load dependency? Obviously EQ can solve it but maybe for some a specific op-amp that just lowers the high frequencies a 0.5 / 1 db etc
 
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amirm

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So I know nothing about op-amp's but would it be possible to find an op-amp that helps the load dependency?
Unfortunately not. The op-amps are on the input driving the class D amplifier where the load dependency is.
 
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amirm

amirm

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Obviously EQ can solve it but maybe for some a specific op-amp that just lowers the high frequencies a 0.5 / 1 db etc
Oh, you can't do this blindly as what you get depends on the actual impedance of your speaker and not just my 8 ohm graph. In reality the high frequency impedance of your speaker is variable so the response variation in high frequencies would likewise modulate. Here is a sample speaker impedance graph:


index.php


Notice how the response varies around 6 to 6.5 ohm above 5 kHz. Every speaker will have a different range of values there, impacting the amplifier differently.
 
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amirm

amirm

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Good to see some vent holes on this model... and cheers to @amirm for the time taken to test this amplifier.
Thanks for posting the pictures. The entire case acts like a heatsink here so the holes are not that necessary.
 

TheWalkman

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Glad to see Fosi tweaking their 3255 amp design by adding vents in the case, higher voltage capacitors, etc.

(I hope the folks at Aiyima are reading this!)

For anyone interested, here’s the coupon:


Get $10 off New Arrivals, Code: V3D10​

 

alvigg

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I have one on order. Amir have you tried remeasuring after Opamp rolling? On this or any similar amp?
 

UrSv

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Power = V*V/impedance. That raising to power of 2 gives you a lot of boost.
Still odd though. The 48 V PSU has 1.5 times higher voltage so that means 2.25 times higher power. 89/34 is about 2.62 so at least one value is off.
 

Fosi Audio

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Really appreciate Amir's measurement and review. :)


Again, we'd like to share an exclusive promo code with ASR members to save $12: FAV3ASR12

This promo code applies to all sales channels including Amazon, Aliexpress, and our official shop.
 
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