Fosi V3 - integrated amplifier

Amazing tiny amp

[Italian version here]

Product: Fosi V3 - integrated amplifier
Manufacturer: Fosi Audio - China
Approx. price:
V3 without PSU: 62,39$
V3 with 32V/5A PSU (as tested): 79,19$
V3 with 48V/5A PSU: 106,87$
Reviewer: Lucio Cadeddu - TNT Italy
Reviewed: June, 2023

[Fosi V3 - front view]
[Fosi V3 - front view]


The Chi-Fi wave (Chi-Fi stands for Chinese HiFi) seems unstoppable and more and more products are flooding the market. Fosi Audio is a small company with commercial headquarters in the Longgang district (Shenzhen, China) and a factory in the Longhua district, also in Shenzhen. We will soon publish a small factory report with the help of our kind Chinese collaborator Cora Chou. Fosi Audio has an extremely vast offer which they are going to expand further. What was missing, perhaps, was a small, super-minimalist, high power integrated amp. They launched a fund raising campaign on Kickstarter, and after a short while the V3 has finally come to light. Fosi Audio baptized it as “Audiophile Amp”. Let's see why.

A closer look

[Fosi V3 - datasheet]

The V3 is a small integrated amplifier with a single line input, a volume knob (which acts as a rotary on switch), an external 32V power supply and that's it. Ah no, actually there is a pre-out (on minijack) to control a possible active subwoofer. Oh yes, the package also includes a bizarre metallic carrot-colored volume knob that can easily be swapped out for the black one (but why then?). Nothing else: no built-in DAC, no multiple inputs, no headphone output, no remote or display. This minimalism, now even a little out of fashion, wouldn't be enough to define it as an audiophile amp, of course. At the heart of it all is a TPA 3255 chipset, claimed to output 150 watts per channel (peak) into 4Ω. Sifting through the official datasheet carefully, the values ​​are greatly reduced, but let's say that on 8 Ohm, with low distortion, we are easily above 50 watts per channel, that's quite a lot if you consider the size and cost of the unit.

Looking closely at the power vs THD curve declared by the chipset manufacturer (see pic), it seems that at 8 Ohm you can get 100 watts with 0.01% of THD, though using a 52V power supply. In this case the power supply is 32V/5A (but you can get the 48V power supply for another 60$ or purchase the amp already with the 48V PSU), so I think the real power output of the V3 is closer to 50 than 100W. The TPA3255 should be able to drive loads up to 1.7Ω. But even this would not be enough to qualify it as an audiophile amp. It is the care in the realization and the choice of passive components that make the real difference: Wima, Elna and NCC caps, Sumida inductors and, as if that weren't enough, interchangeable NE5532P operational amplifiers, so that you can play with some opamp rolling. The whole project, therefore, was ambitious: to create a small, high powered integrated amp, with a top-class sound, well beyond its price range. In fact, the guys at Fosi Audio describe it as “the best-sounding power amplifier in Fosi Audio's history”.

[Fosi V3 - power output]

[Fosi V3 - internal view]

Tech specs

[Fosi V3 - rear view]
Fosi V3 - rear view

Amazing tiny amp

In a market overflowing with small, low-cost amplifiers, often equipped with DACs, remote controls and many other functions, it took a great deal of courage to offer this V3: essential, not exactly user-friendly, truly stripped down to the bone. I still had the Aiyima T9 in my listening room, so I didn't hesitate to use it as a reference, by type and price range. The Aiyima is a Class D/tube hybrid, with built-in DAC, multiple inputs, Bluetooth, tone controls and remote. It uses a very similar chip, the TPA3250, instead of the TPA3255 of the Fosi V3. The cost is similar, a few tens of euros more for the Aiyima.

Let me immediately highlight my first observation: the V3 sounds better. Much better. I don't think the merit lies with the chipset, after all they are very similar, but with the simplicity of the circuit and the excellent supporting components. The difference between the two is significant, practically with all parameters.

This Fosi V3 has a clean, transparent sound, with such a low perceived distortion rate that it constantly invites you to turn up the volume. The Aiyima, on the other hand, appears more confused, at times dirty, vague and, certainly, the desire to turn up the volume is missing. As already written in the review of the T9, in fact, the T9 seems to give its best far from its natural limits. Not so the V3. Thanks to a non-linear volume potentiometer, this little amp starts flexing its muscles much, much beyond the classic 12 o'clock knob position. During my tests the potentiometer was constantly beyond 15 o'clock. Yes, I tend to prefer high listening levels, but certainly this V3 unveils its real power at unusual volume knob positions.

Warning: this doesn't mean that it sounds bad at low volume, far from it: the sound remains full and balanced, defined and transparent even at low volume. The fact is that its cleanliness always invites you to turn up the volume. Now, it may be that with the 48V power supply this phenomenon is lessened, because the output power increases, but with the standard 32V unit the phenomenon is quite evident, so as to be unsettling at first: one wonders where all the declared watts are hidden. Believe me, they are hidden in the final part of the rotation of the potentiometer. Many will not like this feature but, as I always say, don't be afraid to use the whole volume knob, not just its first half!

Tonally, I would define it as neutral, with a very slight tendency to sound open: it certainly doesn't sound euphonic or soft (like the Aiyima, on the other hand) but always taut, rhythmic, even with the most demanding genres. The low range has its best virtues in control, articulation and speed. There's PRaT in spades. Not only that, there is also a lot of energy in the first octave. Thus, both the violent electric bass of Rage against the machine and the subterranean synth notes of Massive Attack are reproduced without fear or noticeable tearing which, for such a small and cheap toy, is surprising.

The midrange is the audio range I liked the most: on vocals it has a clarity and cleanliness that rivals far more expensive amplifiers. The words of the vocals, even in the presence of large choirs, are clearly distinguishable, while the solo voices acquire a truly convincing sense of presence. To find a fault, though venial, I'd say that the lower midrange feels light at times - a feature I've found in other TPA series chip amps - but nothing really wrong. This character lightens lower tone voices a little, but you can live with it. I certainly would.

The high range maintains the same clarity and definition, and gives the listener an excellent harmonic content, as can be appreciated on the plucking of the acoustic guitar, on the cymbals of the drum kit or on the highest notes of the piano and organ. No euphony, as already mentioned, no artificial rounding but, on the other hand, no annoying exaltation.

From a dynamic and energetic point of view, this little guy does not let itself be intimidated by complex musical programs and large excursions. It manages everything with a confidence and absence of uncomfortable compressions, until it reaches its natural limits. The tonal balance doesn't change much, even at high volume, as it doesn't scream, it doesn't sound agressive: it plays loud as long as it has steam reserves. Frankly, I would have liked to test it with a more generous power supply, but Fosi sent a 32V one and I didn't have a 48V one at home. Despite this, the dynamics are convincing, the snare hits are violent when required and so is the kick of the bass drums: full, tense, fast. Compared to the Aiyima, which tended to slow down the bass in the most difficult passages (probably due to the tubes in the preamp section), this Fosi V3 has the grit necessary to give the right rhythm even to the most brutal genres, where a small error in scanning the musical tempo might destroy pathos and involvement.

The three-dimensional image is good, not huge, but still with decent lateral width and depth. The best dowry is the precision and stability focus of instruments and performers, armored in their respective positions, and with very precise contours. For a €100 amp, this is something of a miracle.

Summarizing, I really liked this V3, it doesn't do anything obviously wrong and, until now, it's the best sounding Class D amplifier in this price range I've listened to. The Fosi Audio risky goal would therefore seem to have been achieved: yes, it has nothing obvious to offer, its direct competitors give much more, but when the ball starts, this V3 dispels any doubts about its need to exist in this crowded market. That's all it does, nothing else, but it sounds damn good. A true audiophile amp.

Comments & Complaints


The Fosi Audio V3 will be globally available on June, 20th on Amazon, Aliexpress and the official Fosi Audio website. In case you are interested, Fosi is offering TNT-Audio readers a special discount with a 12$-off promo code: FAV3MKT12 (works on all platforms, just insert it before checkout).


The Fosi V3 is an anomalous object these days, designed exclusively to play as well as possible within an extremely small budget. The verdict is that this result has been achieved in full. Right now, to me, it's the best integrated amp out there at this price point. And the amp plays it fearlessly even in comparison with traditional and non-traditional amplifiers that cost 5-6 times more. It's not user-friendly, it has only one input, it doesn't have Bluetooth or even a remote control: it just plays music, and it does so in an astonishing way.

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