Fosi Audio V3 Mono Amplifier Review

[burkm]

srry for my stupid question...but I want to know if after the 10 mins. without signal it remains hot at around 43° or shuts down completely?

By my observations it cools down a bit in "Auto"-mode. It does not shut down "completely"...

 

[Pulkass]

This is a review and detailed measurements of the Fosi Audio V3 Mono class D amplifier. It was sent to me by the company. The price with the power supply I tested is US $139.99.
View attachment 360697
I must say the concept of a "monoblock" amplifier in such a small size runs foul of any expectation a longtime audiophile would have! But monblock it is even though it is a very small block. Controls are on/off/trigger audio and selection of XLR vs RCA inputs -- just like the big boys! I am not showing the sides of the amp but there are very large holes with attractive orange color grid showing through. Nice. Back panel is again a bit of a shock to the system seeing XLR input:
View attachment 360698

The power supply as noted, is quite beefy with 48 volts at 5 amps on tap (240 watts). The amplifier is stated to have PFFB implementation which for a class D amplifier means it should have no load dependency together with lower distortion. Let's see if we get these with our measurements.

Fosi Audio V3 Mono Amplifier Measurements
Let's start with XLR input:
View attachment 360699
Wow, I did not expect this class of amplifier to break through the 100 dB SINAD barrier but the V3 Mono does exactly that, placing it in our prestigious category of "excellent:
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RCA input costs you some performance but I was relieved to not see any mains interference:
View attachment 360702

Distortion is still at provably inaudible -115 dB. I like that the gain is nominal 25 which is my new recommendation for amplifiers.

Noise performance is excellent and at full power, darn near approaches sate of the art:
View attachment 360703

Now the all important frequency response and load dependency test:
View attachment 360704

There is essentially no impact up to 20 kHz between the 4 and 8 ohm indicating very low output impedance, albeit with a bit of peaking. Compare that to non-PFFB amps such as Fosi Audio V3 stereo Amp:

Above we have 2 dB differential at 20 kHz.

Distortion is very low and only increases with frequency:
View attachment 360706

View attachment 360707

Let's see how much power we can get out of this little box:

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View attachment 360710
Efficiency must be quite high as we get essentially the power we put in (the power supply likely has some headroom).

There is decent amount of power even with 8 ohm and with very low noise:
View attachment 360712

As note though, distortion does rise at higher frequencies:
View attachment 360713

Fortunately it is good where our hearing is very sensitive (below 5 kHz).

I also threw my suite of my punishing reactive loads at it:
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Translating into watts:

View attachment 360716

Amazing that this little amplifier can handle even 2 ohm load! Note that these are short term power ratings.

There may be a bit of power on noise:
View attachment 360718

Conclusions
All I can say is wow! It is incredible how far these small amplifiers have come. It is the result of a manufacturer listening to our needs, implementing features such as balanced and trigger inputs, and proper feedback mechanism to essentially eliminate load dependency. I can't imagine asking for more from Fosi when it comes to such an amplifier. Everything is as good as you could possibly want.

It is my pleasure to recommend Fosi Audio V3 Mono amplifier.

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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/

Nice. I wish they had internal power supply, not that bulky box outside, considering you need two. Oh yes. Or one 10 A. Btw can l change the op amps inside ? What s the best solution?

 

[Killingbeans]

Btw can l change the op amps inside ?

Yes.

What s the best solution?

In terms of op-amps? Probably to leave the factory ones alone.

All of the measurements I've seen from different op-amps in products with sockets have shown sometimes marginal improvement (with doubtful audibilty), sometimes a sh¤tfest of added distortion, but mostly practically zero change. There's absolutely no correlation between performance and price/fancyness of the op-amps, since stability mostly rely on other factors. It's a complete dice throw, unless somebody has taken the time to actually verify the effect of a specific swap with measurements. And considering the data we see in this review, the chance of it being worth the trouble is slim to say the least.

 

[SMen]

This is a great review (I think someone posted the part 1 here or on the user impressions thread)

Part II: Fosi Audio V3 Mono Amp; Class D + PFFB, TI TPA3255 - Retail box with single 48V/10A power supply and filter. [Power, Distortion, and Subjective Impressions.] And on rejoicing over "Solved Problems" in audio.

A blog for audiophiles about more objective topics. Measurements of audio gear. Reasonable, realistic, no snakeoil assessment of sound, and equipment.

archimago.blogspot.com

"The Fosi V3 Mono sounds well balanced and "rich". Some people claim that Class D can sound excessively "thin". Well, maybe years ago this could have been the case but not with modern Class D amplifiers capable of hi-fi performance (low noise, full frequency response, low distortion, excellent transient response); they're just neutral-sounding these days".

Well put (you get down to this after all the measurements). Could not have put it any better.

 

[Sokel]

This is a great review (I think someone posted the part 1 here or on the user impressions thread)

Part II: Fosi Audio V3 Mono Amp; Class D + PFFB, TI TPA3255 - Retail box with single 48V/10A power supply and filter. [Power, Distortion, and Subjective Impressions.] And on rejoicing over "Solved Problems" in audio.

A blog for audiophiles about more objective topics. Measurements of audio gear. Reasonable, realistic, no snakeoil assessment of sound, and equipment.

archimago.blogspot.com

"The Fosi V3 Mono sounds well balanced and "rich". Some people claim that Class D can sound excessively "thin". Well, maybe years ago this could have been the case but not with modern Class D amplifiers capable of hi-fi performance (low noise, full frequency response, low distortion, excellent transient response); they're just neutral-sounding these days".

Well put (you get down to this after all the measurements). Could not have put it any better.

What's worth saying is how gain reflects in it's measurements,specially with RCA input and how a totally decent 91.4dB SINAD at 1kHz/1W goes down to either 79dB for 25dB gain or 77dB SINAD at 1kHz/1W for 31dB gain.
SINAD almost takes the same penalty as the numerical gain increase.

And it's worth noting that every time we see a review we should pay close attention to gain and compare with amp's results of similar gain.
It's extremely rare to see an amp that takes no penalty with higher gain.

 

[JLB321GO]

After seeing the soldering my two Fosi Audio V3 Mono's are going back to Amazon UK for a refund.

This whole V3 Mono story is a true debacle.

First, noise issues, then reversed polarities. What next?

 

[ninetylol]

Ouch at that introduced distortion with rca. Probably still below speaker thd, but that kinda makes the selling point for some of us invalid.

You get more power too yes, but in total to another TPA3255 thats more or less +2db more Max volume.

I still think its a great amp, but I think its not much better than any cheap TPA3255 like a V3 stereo for 1/4 of the price.

 

[JLB321GO]

Sorry to have made many friends confused. We can confirm the phase is the same for both RCA and XLR input based on the measurement using an AP analyzer.

Our engineer connected two V3 Monos, one with RCA input and the other with XLR input. We can find that the phases are the same based on the AP test result.
View attachment 386999

And did you reverse the test also?

 

[burkm]

@JBL321GO
Noise issues ? I never heard of any with my 2x 48VDC / 5A power supplies for 2 amps. Some "noise issues" have been introduced with that 48VDC / 10A power supply for two amps because of users trying to "save money and space" for the power supply. The supplied filter and ist siblings are nullifying this advantage now anyways.

Polarity issues ? I just reversed the speaker connections (banana plugs) which cured any "phase reversals" They will change - probably - the female banana colors on the back plate and the corresponding printing for the next batch. I did this already... It will be only a "real issue" when mixing different amps or systems, otherwise there is "none".

Never mind, aren't You exaggerating a bit ???

 

[JLB321GO]

@JBL321GO

Never mind, aren't You exaggerating a bit ???

I'm just being objective.

 

[DavidM1]

This whole V3 Mono story is a true debacle.

First, noise issues, then reversed polarities. What next?

Funny, I don’t see it that way. I guess it met and maybe exceeded my expectations. I always planned to use balanced inputs and I did what I thought was the obvious thing and chose two 5A power supplies. It is silent, it has heaps of juice, the auto functions without any issue and I feel like it does justice to my equally impressive and affordable SMSL DAC.

It seems every 6 months there is another amp on the market so if you sit tight there will be something new to fuss over. I won’t be changing these though.

 

[burkm]

I'm just being objective.

Are You ???

 

[Basilderat]

Interesting that Archimago measures single-tone distortion when using RCA input as 13dB worse (80dB vs 93 dB) than Amir's measurement.

Part II: Fosi Audio V3 Mono Amp; Class D + PFFB, TI TPA3255 - Retail box with single 48V/10A power supply and filter. [Power, Distortion, and Subjective Impressions.] And on rejoicing over "Solved Problems" in audio.

A blog for audiophiles about more objective topics. Measurements of audio gear. Reasonable, realistic, no snakeoil assessment of sound, and equipment.

archimago.blogspot.com

I wonder if it's because he is using the 10A PSU? He picks up 10-15dB of 60Hz mains hum whereas Amir did not.

 

[Sokel]

Interesting that Archimago measures single-tone distortion when using RCA input as 13dB worse (80dB vs 93 dB) than Amir's measurement.

Part II: Fosi Audio V3 Mono Amp; Class D + PFFB, TI TPA3255 - Retail box with single 48V/10A power supply and filter. [Power, Distortion, and Subjective Impressions.] And on rejoicing over "Solved Problems" in audio.

A blog for audiophiles about more objective topics. Measurements of audio gear. Reasonable, realistic, no snakeoil assessment of sound, and equipment.

archimago.blogspot.com

I wonder if it's because he is using the 10A PSU? He picks up 10-15dB of 60Hz mains hum whereas Amir did not.

It's because his measurements are at 1W and not 5W as Amir's plus whatever sample-to-sample variation may be and gain penalty.
You can see the penalty in XLR input here:

At 5W is 100dB SINAD and at 1W is near 95dB SINAD.

 

[antcollinet]

It's because his measurements are at 1W and not 5W as Amir's plus whatever sample-to-sample variation may be and gain penalty.
You can see the penalty in XLR input here:

View attachment 389910

At 5W is 100dB SINAD and at 1W is near 95dB SINAD.

Plus, Amir puts a lot of effort into the cleanliness of the setup to avoid introducing mains hum.

 

[Sokel]

Plus, Amir puts a lot of effort into the cleanliness of the setup to avoid introducing mains hum.

That's true but in this case (Arch's RCA input) noise competes with distortion at equal amounts.
It wouldn't have a better result even if one of two was way lower.

 

[ninetylol]

That's true but in this case (Arch's RCA input) noise competes with distortion at equal amounts.
It wouldn't have a better result even if one of two was way lower.

Golden sample? I dont think we can critizize archimagos results, He knows what hes doing.

 

[Sokel]

Golden sample? I dont think we can critizize archimagos results, He knows what hes doing.

No,no golden sample as Arch's XLR results are perfectly in check with Amir's.
More like a closer to real life result (well,that can be way worst than the lab conditions) .

And as a matter of fact,80dB SINAD is not bad at all,we're just spoiled here on ASR.

 

[saberger0357]

So is Amazon still shipping the reverse polarity versions?

 

[DCinATX]

So is Amazon still shipping the reverse polarity versions?

Definitely as of last week