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Amplifier Fosi Audio V3 Mini Stereo Amplifier Reviews

Fosi Audio Team

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Fosi V3 Review

So why try a Fosi V3 when my studio has a full active Paradigm Reference 5.1 system and I also have a Denon receiver for project power? Well there were two reasons, the first being all the positive reviews from diverse users regarding a small factor class D amp and secondly, I am designing a 3d printed turntable and want a very compact system for demo days.

The amp has been put into service powering a dsp controlled open baffle speaker I created from drivers I had lying around the studio. The portable requirement and open baffle was a perfect fit and enter the Fosi! The speaker is an unholy match up of a Celestion 12" Seventy 80 16 ohm guitar speaker and a 1990s Radio Shack 4" 4 ohm coaxial car speaker mounted to a piece of 3/4" plywood. On first power up the whole thing almost ended up in the bin, but..once the dsp crossover and eq was applied, it came to life. Driving an open baffle with a 12" driver is no small task to keep the excursion controlled and tight but the wee amp is doing the job extremely well! It is also using the stock power supply and at normal listening levels, transients and details are excellent.

The combo of the open baffle and the Fosi produce sound, especially for acoustic pop and jazz, that is surreal! It is almost like the artist is in the room with you. This effect of open baffle dipole speakers is well documented but being able to do it with a cost effective amp the size of a paperback and some leftover speakers is in fact a game changer.

I normally work with large systems from Meyer and L Acoustics and such and using DSP is a given, but bringing this tech down to numbers individuals can afford is what we have here. The system will be tuned and a second speaker will be built (this test was in mono) as well as another Fosi V3 will be added to create my demo rig to show of the turntable.

I have to thank Jerry from Fosi for sending me this lovely little beast to test and I am truly happy to have seen something very different and useful!

BTW, the Fosi sounds much better than the old Denom AV receiver.

•Compact size
•Very smooth sound for a class D amp
•Adequate power from supplied power supply for conservative listening levels
•Handles large drivers in an open baffle speaker very nicely

•binding posts very close together
•small power supply as standard
I’m amazed at what this little amp can do in my main system, driving a pair of single driver full range floor standers. It was only meant as a stand in whilst my tube amp gets fixed, but the drive and clarity are really eye opening. However, I did notice it falls apart somewhat with complex material, it becomes very hard to distinguish what’s going on, like my brain can’t quite decipher the wall of data into actual music? I wonder if this is a Class D problem, as I’m thinking of building a Hypex shortly and was hoping someone here might have experience of higher end designs?
Fosi Audio V3

I wanted to share with you another of my passions and one of those little diamonds that sometimes break into the audio market.

The Fosi Audio V3 is a little gem that doesn't need much light to shine.

What is it about?

From a minimalist amplifier from the company Fosi Audio, a brand that for some years now has been positioning itself as a reference in a market range that did not exist before.

HI-FI has historically been inaccessible to the general public.

Fosi is offering products with a high level of quality at a very competitive price that allow you to enjoy quality sound at a reasonable cost.

A great advantage of globalisation and new communication channels is that the customer/brand relationship has changed radically. In this case, the FOSI brand listens to its customers and takes their opinions into account in the product development phase.

Something unthinkable a few years ago and that changes the rules of the game, the client no longer buys what a brand has designed according to their ideas, the client is part of the project.

What does the FOSI V3 have to offer?



In a very compact enclosure measuring 105x143x40 mm there is a well thought-out selection of components which show their full potential in the sound test.


Large selection of components

The minimalist design features a front panel with an operation indicator LED and a volume adjustment dial with a very good feel and a silent connection - "there is no expected connection noise/pop".

There is no remote control and I don't think it is necessary, if you use it as a desktop amplifier it is within reach and if it is a remote installation, remember your old school days without this accessory.

The rear is still minimalistic, with RCA signal input connectors, speaker output with screw/banana plugs and a 3.5 mm stereo output with fixed signal level independent of the front fader.

Fosi indicates in future revisions of the device that it will be variable depending on the front-end controller.

For this test I have two V3 units, a 32V and a 48V version.

It is the same device where only the PSU varies, the 48V PSU is larger than the V3.

The listening tests were carried out with HECO VICTA PRIME 302 loudspeakers and a S.M.S.L DO300 DAC.

Two configurations

Configuration 1 - One V3 unit in normal connection mode

Configuration 2 - Bi-wiring mode with two V3 units (32V-48V)

The sound tests


Component preparation


PSU (Power Supply Unit) Comparative


Tests in bi-amplification mode


Adjusting audio levels and format

Wait a minute, where is the secret camera? How is it possible to obtain this power with these micro dimensions?


Declared power

These are the declared maximum power ratings, in the range of 20 to 20000 hz and with Thd < 1% they are lower but sufficient to drive any box on the market with quality.

Depending on the installation, we have a power of 60 to 100 watts per effective channel.

The Heco 302s offer a sensitivity of 90 dB 8 Ω - (2.8V/1M) and during tests with the 32 V and 48 V versions they perform well.

The potentiometer offers a logarithmic curve in its operation, this allows a more precise adjustment when using a lower volume, it may seem strange to you but it is a feature commonly used in professional audio.


The hated but necessary connecting cables
So 32 V or 48 V? It all depends on the set and the power you usually use.

If you want quality sound at low volume, the 32 V version is sufficient.

Is your installation demanding? Use 48v

The sound is balanced and there is no background noise. You can position the instruments in front of you and the timbre is completely neutral.

This sound will always depend on the speakers you use in your installation. The V3 is only a neutral link in the sound chain, it does not colour the signal.

For the V3, Fosi offers the possibility to replace the standard NE5532 operational amplifiers.

The V3 is compatible with a variety of dual 8-pin op-amps such as Sparkos SS3602, MUSES02, OPA2604, OPA2134PA, OP249, AD827, RM4559, LM4562, LME49720HA.

This level of customisation allows the user to easily modify the personality of the amplifier.

Across different musical styles, from classical, pop, rock to techno, the V3 shows no fatigue or distortion.

The Texas Instruments TPA3255 chip does an exceptional job, during testing and using bass-heavy techno music the external temperature of the V3 did not exceed 40ºC with a start-up temperature of 30ºC.

(Spain, August 2023, in the middle of a heat wave).


Bi-amp & crossover mode
In the bi-amplification tests I used the 32V version to feed the treble and the 48V version.


This results in an improvement in sound clarity, an improvement in detail as more dynamics are available to work with the loudspeaker.

In future tests I will perform a signal filtering prior to V3 to assign a frequency range to each V3.

The usual version on the market is the 32V version (32V/5A external power supply), although there is also a 48V/5A power supply version and a V3 only version without power supply, different options for different equipment. This, together with the possibility of customising the device, makes it a very useful component in the usual jigsaw puzzle that is high-end sound equipment.


A must-have component in primary, secondary and desktop systems.


Quality of construction

Value for money

Power module performance

Possibility to customise operational amplifiers


Remote control? May be necessary in some cases

Unregulated pre-output output.

In the same case as the remote control, a large majority of users do not use this function.


Max Power Output:
300Wx2 @4Ω

SINAD: ≥88dB

SNR: ≥110dB

Terminating Impedance: 2-8Ω

THD: <0.003% THD: <0.003% THD: <0.003% THD: <0.003

Power Amp: TI TPA3255

Op-Amp: TI NE5532 x2

Power Supply: 32V/5A, 48V/5A

Power Input Range: DC 24V-48V

Frequency Response Range: 20Hz-20kHz(±0.1dB)
Hi everyone,
Here is my review of the FOSI V3 amp in 48V.


Right out of the box, I am really impressed by the build quality of the amp.

Indeed, the V3 gives a more upscale impression. The paint is of excellent quality, the assemblies are perfect, the volume button is very pleasant to use. It is also the only button on the amp that also acts as an ON/OFF button.

Fosi Audio had the good idea of perforating the chassis on the top and bottom. So the air circulates well, the amp is just lukewarm after several hours of operation. .

The sockets at the back are a little close together, and so if you have thick fingers it's not always easy to use the screw connectors for the speakers, it's better to use banana plugs. Otherwise apart from an OUT output (which I have not tested) there is only one RCA input. At least the V3 is compact and doesn't take up space.

You can easily open the cover to change the original AOP, NE5532. They will change the sound signature of the amp, here are different compatible AOPs (Some are more expensive than the amp!!!): MUSES02, OPA2604AP, OPA2134PA

The 48V power supply is as big as the amp...

Sound rendering:

Here is the equipment used: my RECITAL AUDIO DEFINE, powered upstream by a HARMAN KARDON AVR645 and an FX AUDIO tube preamp (Raytheon Tubes) and finally the Fosi Audio V3 at 48V.

I also did some tests by connecting a DRAGONFLY BLACK DAC directly to the Fosi amp.

I turn the volume knob and a pleasant click is heard, and music starts coming out of RECITALs.

Despite the 48V power supply I find that you have to turn the volume knob quite a bit to get a loud enough sound. But by turning the knob more than 80% the sound becomes very loud. In any case, it’s more than powerful enough for my living room!!!

For the sound, we still find this quite impressive sound quality given the size of the amp and the price (around €100...).

The treble is very detailed, the stringed instruments sound very good, in short, nothing to complain about.

The bass is powerful and it goes down low with a nice depth, the amp has no trouble moving the Recital bass driver.

The paths are clear and perfectly in place.

The sound of the Fosi V3 is neutral than the A07 with a hint of warmth in the low midrange.

In conclusion,

The FOSI AUDIO V3 amp is an excellent amp, the sound is excellent, the quality of finish is TOP and for the price, it's a gift!!!

It will be ideal in an office with quality speakers, and even in a medium-sized room the power will be sufficient. Connected to a power amp behind a somewhat soft HIFI or home cinema amp, it will wake up all that!!!

Of course, there is no remote control and only 1 line input but at this price...

Ampll V3 is recommended.

Video of the test :

Really enjoying my V3 amp, it has been particularly useful because of the tapered volume pot. It is nicer to use in settings where one wants to be able to play at softer volumes (dining room, bedroom). It never gets other than warm to the touch when using 32v and 36v power adapters. I like its straightforward design and clean appearance. I've recommended it to a number of friends and music enthusiasts. While Aiyima makes some good competitive products, I think the V3 is still the champ of the Class D mini-amps. Fingers crossed for some true monoblocks without volume controls from Fosi down the road!
Many people say it’s good and leave many people in doubt, but sometimes you just really have to see it all for yourself and enjoy what you have. And that’s what I did. In this review I will give insights, criticism and final thoughts about the Fosi Audio V3.

Light disclaimer; The setup I am running is a FiiO KA3 as a DAC, running to a splitter going to RCA cables into the amplifier. My speakers at the time of review are the EPOS M12.2. Results from the amplifier may vary from speaker to speaker.

(Desktop amp configuration)

From the time of unboxing, you’ll be greeted by the cute unit that is the Fosi Audio V3, my mom refused to believe that this was an amplifier.
The Volume knob is special, it has a logarithmic potentiometer, so instead of hearing your volume go up in a straight line, it’s kind of a curve meaning that you have more fine adjustment on your sound level. The knob also goes up until it points almost exactly 90 degrees down which is funny having always seen volume stops at around 4 o’clock and a half.
The back of the amplifier has RCA stereo input, 2 pairs of speaker binding posts and a singular 3.5mm line out.

The criticism for this amplifier that I have is not very special. The experience I've had up to this moment has been very pleasing, but some things just surprise me every time.
The build quality of the unit itself is very good to say the least. It is made out of metal, has quite a little bit of heft to it, but when you see it in its place you really question if this thing is really capable of delivering some power seeing its size. To say that this thing is good is an understatement, I would say it is even excellent. This amplifier with the speakers that I have right now is a match made in heaven. I had a better experience in my own home than listening to a reference setup in my local audio shop completed with a preamp, amp and a pair of 30K$ floorstanding speakers. I have heard things that I never thought I would hear in my songs, it’s a new dimension, my mom almost even cried while listening.
The whole stage is brought to be when I play the right songs at the right level, it really brings out the best, the separation is insanely good, my mouth was wide open the whole time I first listened. The Fosi Audio V3 keeps on giving until this day.
It powers my current speakers like a charm, it was a well done upgrade to everything I ever heard. It effortlessly powers 8 ohm speakers to good levels.

Listening to The Weeknd’s song “Starry Eyes” you can basically hear things above you going around, also the song “Take My Breath” you can hear the synthesized voice at the start precisely where it is at all times, that’s how good the amplifier does at separating and spreading the output.

My final thoughts on this little beast is that it is something that is mind blowing, with the right cables, DAC and speakers you can achieve bliss. It punches way over its price range, you could tell me that this isn’t a 30K$+ setup and I wouldn't believe you. The sheer modularity that you can have on this, being the op amps and the power brick is something I can't get my head over. Fosi Audio has genuinely impressed me, and it is now one of my favorite companies.

The Fosi Audio V3 is Gab Approved.