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Amplifier Fosi Audio ZA3 Balanced Stereo/Mono Amplifier Reviews

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Here is the index of the videos and articles reviewing ZA3.

Title and Link​

Fosi Audio will DESTROY the Hifi Establishment with the ZA3 AmplifierVideo

Why you need a mono amp in your systemVideo
Fosi ZA3 TPA3255 Mono/Stereo Switchable Amplifier, and...Article
Fosi Audio ZA3Article

Michael Andrew​
Fosi Audio ZA3 Review: ChiFi Redefines HiFi!!Video

Honest Audiophile​
Fosi Audio ZA3 - Balanced Stereo & Mono Speaker Amp for $125?Video

Forever Analog​
Fosi ZA3 vs V3 vs Aiyima A07 Max - Which is the right amp for you?Video

ABX Audiophiles​
Hello hobbyists and Fosi,

This is my first time buying a chip amp and it's because of Fosi and their customers positive reviews that made me write a review.

I stepped away from audio for about 10 years.

A friend of mine pointed out a $300 dollar pair of speakers I might be interested in. These little speakers have a lot of hype, and then I notice Fosi on you tube, more hype, Fosi started the sparks even more. My hobby came back to life, no joking, it really did.. the sparks of joy in audio became more of joyful affect when I bought this za3 amp.

Thanks to the reviews, thanks guys. I pulled the plug.

I took a chance on buying the za3 and all I can say is.. wow.. I'm glad I did. One reviewer on you tube said, "It's good for back ground music" paraphrasing here.. but that is a complete sad joke. Not true.

I think this man never swapped enough equipment to find his weakest link, and hardly broke it in. The za3 in my strong opinion is not the weakest link. It's awesome.

I had amps in the price range of 5k all the way up to 18k.
Thank God some of them were in mint condition and used.

Most amps I bought were brand new, but I'm just trying to give you an idea of how amazing this little amp is.

I'm not bragging, it's far from that. I feel I wasted a lot of money with pricey amps and I am far from rich or even far from upper middle class, but I gained a pain staking lesson along with a trained ear, but the addiction for audio can make you a poor man, be careful people.

I don't want jewelry and what I learned is, you can make anything look good, whats more important is, it's in the inside that counts, and that is the circuit. Organic realism comes to mind when I hear this amp.

Here comes Fosi.. and Fosi, thank you so much for reaching out to people that can now afford audio fedelity and enjoy it at an affordable price.

I can no longer afford high priced audio and I turned away from it because of the insane high prices And lost quite a bit.

Fosi can stand up to those big guys. Yes, this little but big sounding amp is that good, and it might be even better if you try it out for yourself.

Just because you spend more, doesn't mean you'll be happy.

In my experience, I waited days and months to break in some units, and they never changed for the better. This amp did for the better

I wish the new mono blocks came out before, or at the same time the za3 was around. I would have waited for the mono blocks.

While I'm writing this, my second za3 is on it's way.
Hard to wait any longer. Lol.

Here's my almost one month experience with this little gem. Let it break in for at least 300 hours. Leave it on.

I was blaming this amp for sounding thin and bland and it really changed a few hours afterwards.

This amp has the capability for you to hear whats the weakest link in your set up.

Dont blame the za3 because of the price, you will be mistaken and get stuck in a merry go round like I did many years go.

I have no embarrassment expressing this, I am making no money doing this and I dont expect anything in return.

There are many snobs in this hobby that wanna trash a lower price product.

It's a very fine and affordable product and it's bursting a lot of bubbles.🤣

My za3 is connected to Tekton Enos. 94 dB and the book shelf speakers are 84db sensitivity and the za3 handles them with no problems, 8ohms.

Thank you Fosi.
I received my via their Kickstarter program at roughly $125 with the 48V power supply and thought I would post my review here for the benefit of the community:

Fosi Audio ZA3

What is in the Box, internals and overall Build Quality​

The ZA3 arrives in a larger package compared to other Fosi amplifiers. Contents include the ZA3 amplifier itself, a robust 48V 5A power supply unit (PSU) similar to the one that comes with the V3, and a comprehensive manual detailing connectivity options.

Note: depending on your order you will also either get an orange or a black volume control, I picked the orange one.

Here is the excellent power supply:

IMG_9134 Medium.jpeg

Internally the ZA3 is as nicely built as it is externally with the opportunity to swap out the NE5532 op-amp’s for tweaking the sound.

The build quality is outstanding, basically using the lesson learned with the V3, Fosi Audio have gone up to the next level with this Amplifier. I love the little design touches for example the quality of the vent holes on the side have a certain class about them:

side view.jpeg

The ZA3 is a little bit bigger than the V3 and the new Aiyima A07MAX:

IMG_9040 Large.jpeg

This photo from above really shows how much larger the ZA3 is:

IMG_9042 Large.jpeg

The extra size does allow more space for more connections (which I will get to in the Features section below) but also more space between the binding posts.

IMG_9043 Large.jpeg

Though what really sets the ZA3 apart from these 2 other class D amplifiers is its feature, lets look at the features now in detail:


Compared to the Class D amplifiers that Fosi Audio have previously released, the ZA3 has many new features specially designed to get the best sound quality out of your system. The features alone make it a significant device in the history of class D amplifier, this is the moment when Fosi Audio have upped their audiophile game and we the users who appreciate great sounding music benefit from the extra quality audio experience the ZA3 helps to provide.

Volume Control / Power toggle​

Some recent Class D amplifier can only be turned off my moving the volume back to 0 but for a Mono block especially this can be problematic, not so much with the ZA3. You can fix the volume and press and hold the Volume button to switch on the ZA3. Therefore, when you have matched the volume on 2 setup as monoblock it is key not to have to touch the volume again (typically you would control the volume to both ZA3’s via a pre-amp or in my case via the WiiM Pro Plus).

Mono Switch​

The Mono Mode switch on the front of Fosi Audio ZA3 is a probably its key new feature, enabling users to get the benefits of more power from 2 ZA3 acting in parallel, one ZA3 feeding the left speaker and the other feeding the right Speaker.

Here are the back of 2 ZA3 setup in Mono block mode, in this case one ZA3 is handling the Left and the other is handling the right:

IMG_9054 Large.jpeg

I also subjectively thought this not only provided more power but a cleaner signal, where there is no chance of channel leakage within a ZA3.

Balanced Inputs (as well as the usual RCA)​

Another of ZA3’s standout features is including balanced RCA and XLR/TRS inputs, offering versatility and improved audio quality. Here is an example where I have feed a TRS input into 2 ZA3 to provide extra clean audio using the Mono block setup:

Here is the back of a ‘fully loaded ZA3’ where both the balanced and RCA inputs are connected:

IMG_9130 Medium.jpeg

Simply using the RCA/BAL switch on the front will select the appropriate input. It should go without saying that a Balanced (XLR or TRS) input will potentially have less noise than an RCA but in practice the RCA will also be incredible clean sounding.

Subwoofer Output​

It also features a proper subwoofer output, so unlike previous Class D Amplifier that had a ‘aux out / subwoofer out’ this is a dedicated subwoofer that is controlled by the volume so can be blended with your speakers to provide that extra sub-bass when required. For example, here is an example of a measurement I made with a subwoofer added to the ZA3 providing subbass down to 30Hz where my speakers were rolling off at 50hz:
I believe the sub-woofer output also has a fixed Low pass filter of 300Hz but there is no high pass filter on the speaker output when the sub-woofer is connected - something to work on in a future version in my opinion.

12V Trigger input​

The 12V trigger input for integrated system control, currently I am using a Wiim Pro Plus as a Streamer and DAC feeding the ZA3 and using the trigger to wake up the ZA3 whenever the music is about to start playing.


So one nice side effect of this feature is the Amp is only drawing power when its music. A quick comparison of the energy used when in Standby waiting for a trigger and being triggered and playing music is:

ModePower used watts
Here is a typical 3.5mm trigger needed for the ZA3 (to work with a WiiM Pro Plus I had to buy a 3.5mm to 2.5mm cable such is the inconsistencies with trigger cables):

IMG_9131 Medium.jpeg

Because the Amp is switching itself on there is no danger of a power on signal damaging your speakers.

Sound quality, Measurements and Specifications​

The ZA3 exhibits clean, powerful sound with excellent stereo separation (especially when used as Mono blocks). The sound will be punchier compared to similar amplifiers due to its neutral frequency response (some similar priced Amplifiers will roll off before the sub bass and roll off the upper treble regions and therefore will not sound as rich and dynamic as the ZA3), When you then add a subwoofer to the ZA3 it is no competition at all with similar priced Class D amplifiers, the ZA3 has a unique set of features at this price point. The unit runs cool even at higher volumes, maintaining energy efficiency.

I will update this review with independent measurements when they become available but currently the official measurements provided by the Fosi Audio for the ZA3 have a SINAD value of 88db which is exactly the same as the Fosi Audio V3 and I would imagine independent measurements will back up this value. The SNR of 106db is actually better than the V3 (but again would need to be verified independently).

Specifications - I have highlight the key measurements below:

  • Amp Chip: Texas Instrument TPA3255
  • SINAD: 88dB
  • SNR: 106dB
  • Dynamic Range: ≥106dB
  • THD: <0.005%
  • Terminating Impedance: 2-8 Ohm
  • Rated Output Power:
    • Stereo Mode: 180W*2 @ 4 Ohm
    • Mono Mode: 240W @ 4 Ohm
  • Frequency Response: 20Hz-20kHz (‡0.1dB)
  • Power Input: DC 24V-48V
Overall these are exception, but its probably worth nothing that when in Mono Mode you do not get double the power as each ZA3 would get a max 240W into 4 Ohms.

What could be improved​

Very little at the price but possible the following could be implemented in a future ZA3 (maybe the ZA4):
  1. Move mono switch to the back (or underneath as with the Aiyima A07MAX)
  2. Add a switch and implement a High pass filter on the outputs to further take advantage of the subwoofer output.
  3. An implementation with Post Filter Feedback (PFFB) - this is an extension of the TPA-3255 design to better handle distortion and provide a more linear frequency especially in the upper treble when connected to specific speakers with high variations in speaker impedance.
    This will also improve the already impressive THD+N / SINAD of 88db
  4. A trigger out to pass the trigger onto a second ZA3 - this would be useful when the ZA3 is set up as a Monoblock, but you still want triggered input to wake both ZA3’s.
  5. A remote to switch the inputs and control the volume


The ZA3 represents in my opinion, tremendous value for money and has some outstanding features like support for subwoofer, trigger input for the price, coupled with a really nice design and excellent measurements this is a top pragmatic choice.

The Fosi Audio ZA3 is an impressive amplifier, offering high-quality sound, versatile features, and efficient operation. Its ability to run cool, coupled with its mono block support and balanced input options, positions it as a competitive option in the audiophile market.
Awesome review..
I have doubts about the usefulness of the mono-stereo lever. Once you've defined your setup, what's the point of changing from mono to stereo? Wouldn't it be better to use the lever instead for an LED or for on/off or as a subwoofer control?
I've been genuinely impressed by the performance and quality of the Fosi Audio ZA3 amplifier. The sound is clear, powerful, and detailed, while its compact design and sturdy build make it perfect for small to medium spaces. I appreciate its versatility, as it can be used for both stereo and surround sound systems. It's truly an excellent value for its price, and I confidently recommend this amplifier to all high-quality sound enthusiasts!
I've been looking for a small balanced amplifier for my desk for a long time. I've tried about a dozen different amps; most of which were not balanced because most balanced amps were outside the price I was willing to pay for a desktop amp, and was okay with a few of them and disappointed with the others.

The Fosi has been the amp I was looking for and I have been nothing but happy with the audio quality. Overall, I am incredibly happy with the the amp and am so glad Fosi released it.

There is one feedback I can provide, and it's relatively minor and maybe just myself, but I don't like the volume knob being the power button. I would prefer a dedicated power button on the front of the chassis, if that's possible in a V2.
Hace 40 años que vivo el mundo de la alta fidelidad, más concretamente el mundo del audiophil, del cual me considero pionero en España, en donde hace 40 años nadie sabía lo que dicha palabra significaba.

Gran sorpresa la mía con esta adquisición ZA3, que de momento estoy probando en modo estéreo y, no me puedo creer que un amplificador tan minimalista y de clase D esté compitiendo en mi casa con un HEGEL H20, un Musical Fidelity M6 500i o un previo Proton AP-1000 + etapa D-1200... increíble!

Lo instalé para probar con unas cajas Dynaudio 52 Audience, luego con unas recién adquiridas LiiSong Emmo Fast-6 (full-Range) y como son cajas pequeñas, compenso graves con el previo Proton AP-1000 y una etapa NAD-216 que alimenta un subwoofer Focal pasivo de doble bobina.

También lo probé con unas recién restauradas Focal Audiom 600L y en todas las pruebas el resultado a sido francamente inesperado... Bravo! Tan contento estoy que ya he comprado una segunda unidad para configurar en doble-mono balanceado, aunque en estéreo la diafonía es absolutamente brutal, la profundidad exquisita en los detalles, sutil, maravillosa, excelente trabajo el de Fosi Audio.

En un sector en el que cada vez hay más "literatura barata" sobre lo que es "audiophil" y lo que no lo es... no sabría qué decir, o mejor dicho si hay algo que decir es que.... señores, señoras... esto suena muy bien.



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Bought 2 ZA3 as well as 2 of the 48VDC Power supplies to go with them listened to them for a couple of hours on a pair of efficient 92db Energy tower speakers then compared them to a high end Sony AB power amp running a pair of Martin Logan's. They equated very nicely in both circumstance's much better then I thought they would be. So quiet surprised to say the least good job Fosi
I've been out of audio for several years, jumping back in now. This ZA3 looks like a 'must have' item. Can you suggest any home audio components that can utilize the balanced inputs? I've only found a couple, and those are on the commercial audio side. System will be minimal, open baffle speakers and OB subwoofer that I am building, CD, possibly Bluetooth unit like the Auris Blume, although I see the Denon ProDN-200BR does have balanced outputs, so that's a possibility. Anything else I could consider? Thanks!
check out Rolls audio.. MB15B and ifi 15v walwart power supply.. the rolls converts rca to xlr.. and it's clean as sounding as heck.. it turns my Conrad Johnson signal to xlr.. hope that helps