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Fosi ZA3 Review by KonusAg

Audio amplifier device review: Fosi Audio ZA3
This is the second review I have written relating to a product from the FOSI brand, the first was relating to the Fosi K5 Pro Dac Gaming Audio, you can find it here:
while this refers to the FOSI ZA3 audio amplifier, with integrated TPA3255 high-end Class-D amp. which can be used in mono mode paired with another, or in classic stereo mode.
The product comes in a black and completely metallic case, with a veryminimal control panel, which includes:

  • Volume knob with integrated pressure ON/OFF system.
  • On the left a toggle switch for input selection between XLR and RCA.
  • On the right, a toggle switch that selects Mono/Stereo operation.
There is no IR receiver for remote control, so everything is managed locally like the 'PURE' amplifiers, without too many frills.
The equipment includes :

  • Amplifier.
  • 48 VDC 5 A or 32 VDC 5 A power supply.
  • The manual.

The amplifier features on the back :

  • 2 Balanced XLR inputs
  • 2 speaker outputs for cable / connector 2-8 Ohm
  • 1 exit for SUB
  • 2 classic RCA inputs
  • 1 Jack 12 V trigger input (for remote ON)
  • 1 input for 32 VDC / 48 VDC power jack

The specifications are as follows:

Channel: 2.0Amplifier
Chip: Texas Instruments TPA3255
SINAD: 89dBSNR: ≥106dB
Dynamic Range: ≥106dB
THD: <0.006%
Speaker Impedance Compatibility: 2-8Ω
Rated Power Output:
With 48V/5A PSU
Stereo: 180Wx2 @4Ω
Mono: 235Wx1 @4Ω
With 32V/5A PSU
Stereo: 95Wx2 @4Ω
Mono: 110Wx1 @4Ω
Frequency Response: 20Hz – 20KHz(±0.1dB)
Input Voltage Range: DC 24-48V

The power supply in my case is 48 VDC 5A, with considerable dimensions.


My first listening test was as seen in the photo below, conceived by connecting the XLR inputs present in the ZA3 to a Fiio K5 docking station, which also offers 2 3.5 mm jacks as balanced output on R and L.
The source associated with the docking is a Fiio X3 2nd generation, one of the first portable Fiio players with that form factor (I also own the X1) which it closely resembles.)

Let's not forget the speakers connected to these 2 jewels, 2 Indiana Line Tesi 560.
They seem to have been created for each other, connected and off you go, no background hiss and a lot of beautiful sound. I'll start by saying that this is the first time I've used balanced cables with XLR connectors and from the little I know they are used for connecting microphones and audio systems with mixer, immune to disturbances due to large cable distances.
Contained in the Fiio there are many songs in FLAC format, therefore with great definition in detail, and when listening with this ZA3 amp I was able to appreciate the spatiality of the reproduced sound expressed as separation between audio channels at the moment of generation but reunited once reached my ears. This is honestly the first thing I appreciated, the second is that my 11 year old son, climbing the stairs while I was listening, exclaimed 'GREAT SOUND', all his father...

My second listening test was, as can be seen from the photo below, conceived by connecting the RCA inputs of the ZA3 to a decidedly more recent portable player in my possession, namely a HIBY R5 Gen2, taking advantage of the headphone output connected to the specific cable.
For this test I moved to a desktop context, i.e. on my desk where I plan to keep my FOSI ZA3 connected to the PC through a Cambridge Magic 100 DAC, and in this case the speakers were downsized to the smaller Indiana Line Note 250 X.
'Nothing else matters' by Metallica is the first song in FLAC format taken from the Sinology Server where I keep the liquid music, which I play with the listening system, and I must say that apart from the slight lack of deep bass due to the not generous Woofers of the speakers, the spatiality remains precise and defined even at high volumes.
Then switching my HIBY to class A mode, warm nuances are added to the spatiality I was talking about before.
'Unfinished sympathy' in the orchestral version of Hooverphonic live at koningin elisabethzaal 2012, adds the theatricality of large live environments and the singer's incredible voice seems to come to life on my desk.
I now want to propose the various disassembly phases of the ZA3, useful for upgrading the two operational amplifiers that FOSI indicates can be replaced with other types of op-amps with characteristics of truly demanding audiophiles.

  • With a light lever (with the help of a plastic tool) I extracted the volume knob which is only stuck by interference in the plastic body inserted into the aluminum knob.

  • With this 10 mm insert applicable to a screwdriver, I unscrewed the nut and removed the washer to allow the detachment of the front panel. Needle-nosed pliers are also fine.


  • I proceeded by unscrewing the two screws on the rear panel.

  • Now with the same wrench I removed the two screws from the lower part of the ZA3.


  • This is the result of the disassembled components.


  • It is therefore possible by sliding them, extract the front panel with the two fixing rods, and then the sound card containing the amplification components.




By KonusAg