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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: 214 49.1%
  • 4. Great (golfing panther)

    Votes: 174 39.9%

  • Total voters
    436

Tio

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I have Wharfedale Diamond SX subwoofer which has speaker level and line level input and output.

Is it safe to connect the speaker out from Fosi V3 to the subwoofer speaker in and then from the subwoofer out into my stereo speaker? I read somewhere that is it not safe to do that if using class D amplifier. Thanks.
 

carlo

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From the amplifier's point of view it is extremely unlikely that you will be able to hear any kind of difference.
It should be noted, however, that the Bluetooth of the bta20pro does not have LDAC, so you could also think of a V3 combo with LDAC receiver (for now LDAC receivers are around 40/50 euros)
Make your own assessments. But whichever of these solutions you choose there will be no day/night difference
Thank you for your suggestion. I didn’t know about the existence of Ldacs…. Is there a dac inside? I just need to connect one of them to the amp via rca? Thanks
 

IndieSynth

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I'm curious how much load dependency could be impacting my system. My V3 feeds a pair of Diamond 12.2, which I think would be impacted to some extent. Is there a way of compensating for load dependency with EQ to see if I can tell the difference?
 

carlo

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From the amplifier's point of view it is extremely unlikely that you will be able to hear any kind of difference.
It should be noted, however, that the Bluetooth of the bta20pro does not have LDAC, so you could also think of a V3 combo with LDAC receiver (for now LDAC receivers are around 40/50 euros)
Make your own assessments. But whichever of these solutions you choose there will be no day/night difference
Thanks. I'll think about it. The external receiver could be cool but I'd have to disconnect the RCA cables any time I want to play something without BT....
 

somebodyelse

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I have Wharfedale Diamond SX subwoofer which has speaker level and line level input and output.

Is it safe to connect the speaker out from Fosi V3 to the subwoofer speaker in and then from the subwoofer out into my stereo speaker? I read somewhere that is it not safe to do that if using class D amplifier. Thanks.
It depends in the internals of the subwoofer. If they've treated the black terminals as common then you can't use it with any bridged amp. Bridging used to be unusual, but is now common in Class D chip amps like the V3. If you have a multimeter you can check the resistance between the left and right black speaker input terminals. If it's close to 0 Ohms then don't do it.
 

Tio

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It depends in the internals of the subwoofer. If they've treated the black terminals as common then you can't use it with any bridged amp. Bridging used to be unusual, but is now common in Class D chip amps like the V3. If you have a multimeter you can check the resistance between the left and right black speaker input terminals. If it's close to 0 Ohms then don't do it.
The resistance is around 3.5 when I set my multimeter to 200 ohm measurement. Is 3.5 consider close to 0? thx.
 

somebodyelse

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The resistance is around 3.5 when I set my multimeter to 200 ohm measurement. Is 3.5 consider close to 0? thx.
I was expecting a fraction of an ohm or a few k, so I've probably misunderstood what they're doing. I'd try asking Wharfedale whether it's safe to use with bridged amps. Anyone have a better understanding of this?
 

Tio

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What does your multimeter read with the two probes connected together?
around 4.5. I also try probe the red and black input and it show 1.

I'll stick using source line out into sub line in, and then from sub line out into V3 line in. Thank you very much for all of the replies.
 

T&T

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Dec 17, 2022
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Using Wiim Pro and geshelli akm4499 with sparkos...Aiyima07 Max with Muses02 sound much better than Fosi V3 both with 48v power supply so bye bye V3
 

PlasticDoc

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We already had SINAD, dB, percent, bits and ppm. Now, we have a new measurement: the "much better".

However, it is unclear how this new measurement is quantified (*).

(*) "If we can measure it, we can improve it".
 

PlasticDoc

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Ask ChatGpt to explain what it means "much better"!!!
My rant wasn't about semantics, it was about subjectivism and its units of measurement.

Perhaps the "muses" inspired the OP? Please note that the muses I am referring to are the nine sisters of Greek mythology. They are not the manufacturers of either the opamp or the amplifier.
 
Last edited:

asimze

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Perhaps the "muses" inspired the OP? Please note that the muses I am referring to are the nine sisters of Greek mythology. They are not the manufacturers of either the opamp or the amplifier.
OPA MUSES 02, MUSES 03 ...!!!
 

Abstracted

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Is there a reactive load test?
I'd like to see how it responds to 2ohms.
 

DrSpan

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Feb 2, 2024
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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.
View attachment 293692
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:

View attachment 293693
As you will see later, you really want the 48 volt version:
View attachment 293694

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:
View attachment 293696

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:
View attachment 293697

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:

View attachment 293698

Frequency response shows load dependency which all class D amplifiers in this price range show:
View attachment 293699
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:
View attachment 293700
View attachment 293701

Edit: forgot to post crosstalk measurement:
View attachment 293839

Let's see how much power we can get out of this little box into 4 ohm:
View attachment 293702
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:
View attachment 293703

View attachment 293704

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:
View attachment 293705

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:

View attachment 293706

There is some pop noise when turning on and off but it is very mild:
View attachment 293707

The amplifier is stable on power up:
View attachment 293708

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%):

View attachment 293709

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:
View attachment 294418

View attachment 294419
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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As always, questions, comments, recommendations, etc. are welcome.

Any donations are much appreciated using: https://www.audiosciencereview.com/forum/index.php?threads/how-to-support-audio-science-review.8150/
Thank you for all the work!
If i may wish something for the future it would be a little bit more information in the title or create categories so one can find easier things like

„ Class D Compact power amplifier“ Or Name X Classe D Power Amplifier Review, or Class A Integrated Amplifier etc etc .
Hope what i say makes sense
The way it is not if i dont know what each Amp model is by heart it is impossible to make the search more specific
 

OldTimer

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Nov 24, 2023
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Thank you for all the work!
If i may wish something for the future it would be a little bit more information in the title or create categories so one can find easier things like

„ Class D Compact power amplifier“ Or Name X Classe D Power Amplifier Review, or Class A Integrated Amplifier etc etc .
Hope what i say makes sense
The way it is not if i dont know what each Amp model is by heart it is impossible to make the search more specific
it’s not just the class d amp but tpa3255 chip amp.
 
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