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Amplifier Fosi Audio ZA3 Balanced Stereo/Mono Amplifier Reviews

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Join the discussion on ZA3! This thread is dedicated to users' insights, reviews, and experiences with ZA3. Your feedback is invaluable to our community. Furthermore, you can even showcase the setup you've created using the ZA3 here!


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

Author​
Title and Link​
Type​
Ebetf88oI8ghef_5fCpGw288hdkFIC5IWxY7pm0pgLy8zsEtBCbV0yxf0WRcmgJieYi9v3T7-Q=s68-c-k-c0x00ffffff-no-rj

cheapaudioman​
Fosi Audio will DESTROY the Hifi Establishment with the ZA3 AmplifierVideo
AIf8zZS85NZvwQuApAHZ2UqdOZL-50zHC0dlCkDbMfrV=s68-c-k-c0x00ffffff-no-rj

Masterclass​
Why you need a mono amp in your systemVideo
guddu​
Fosi ZA3 TPA3255 Mono/Stereo Switchable Amplifier, and...Article
jeromeoflaherty​
Fosi Audio ZA3Article
rDqLLodpNQMiJAjT-33s2WaZhYV3cJ7Wxys665DbmjCa3yc3TpZ6nXzRpVBM_Wy4yONYkEQwuQ=s68-c-k-c0x00ffffff-no-rj

Michael Andrew​
Fosi Audio ZA3 Review: ChiFi Redefines HiFi!!Video
AIf8zZSmQ-N_j5YM2O0ND0UvUpsByP0-1On70emi8-t-=s68-c-k-c0x00ffffff-no-rj

Honest Audiophile​
Fosi Audio ZA3 - Balanced Stereo & Mono Speaker Amp for $125?Video
JeQAWRixag2P8BqbYs6NSDswWFf645HOYMXEhkP1w4Wm9eruCiGctFtc3on9hU2Pn5ycRtJDJLs=s68-c-k-c0x00ffffff-no-rj

Forever Analog​
Fosi ZA3 vs V3 vs Aiyima A07 Max - Which is the right amp for you?Video
VFTYF9hzbm7k00Nk5zw5LVFSs8YV_grzO0Qpv-875xSU21FBv_g5LtwCH4CF_pFaU40fISEcAv0=s68-c-k-c0x00ffffff-no-rj

ABX Audiophiles​
BEST ULTRA BUDGET CLASS D AMP OF 2023?!Video
 
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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!
 
Hi,

I have just cancelled my order [on Amazon UK] for two of these ZA3's because I am unclear as to whether the method of turning the amps on and off will work for me!

To clarify: when using my Fozi V3 - which has a latching on/off switch built into the volume control - I have it plugged into a smart plug board.
This allows me to turn the V3 on and off remotely by leaving the volume control at it's set position and simply using a voice command to switch the plug board on and off instead. This works well for me.

Now, according to the manual, the ZA3 still uses an on/off switch integral to the volume control, but instead of being a simple latching switch, it has a press and hold [for two seconds] functionality which I suspect is to activate a relay. And, if this is indeed the case, a voice activated smart plug board would no longer allow for the remote activation of the amp.

Can you clarify if my assumptions about the ZA3's on/off switch are correct and that, as a result, the ZA3's power state cannot be controlled by using the afore mentioned smart socket.

Many thanks.
Phil.
 
Hi,

I have just cancelled my order [on Amazon UK] for two of these ZA3's because I am unclear as to whether the method of turning the amps on and off will work for me!

To clarify: when using my Fozi V3 - which has a latching on/off switch built into the volume control - I have it plugged into a smart plug board.
This allows me to turn the V3 on and off remotely by leaving the volume control at it's set position and simply using a voice command to switch the plug board on and off instead. This works well for me.

Now, according to the manual, the ZA3 still uses an on/off switch integral to the volume control, but instead of being a simple latching switch, it has a press and hold [for two seconds] functionality which I suspect is to activate a relay. And, if this is indeed the case, a voice activated smart plug board would no longer allow for the remote activation of the amp.

Can you clarify if my assumptions about the ZA3's on/off switch are correct and that, as a result, the ZA3's power state cannot be controlled by using the afore mentioned smart socket.

Many thanks.
Phil.
Hello friend,

Sorry for the inconvenience. It's true that ZA3 uses an on/off switch integral to the volume control. When the power is cut off, we need to long press the knob to power it on. In this case, it could be a problem when using a smart plug.😢

We've marked down your concern and we'll probably change the switch mode, like moving the power switch to the toggle lever.
 
Hello friend,

Sorry for the inconvenience. It's true that ZA3 uses an on/off switch integral to the volume control. When the power is cut off, we need to long press the knob to power it on. In this case, it could be a problem when using a smart plug.😢

We've marked down your concern and we'll probably change the switch mode, like moving the power switch to the toggle lever.
Hi, and thanks for the prompt reply.
Yes, moving the on/off switch to a toggle switch would work well with a smart plug board [just like the V3].
And having that switch entirely seperate from the volume dial would, I imagine, suit a lot of other users too.

I just wander how long such a change would take to impliment! Because as an "early bird discount" buyer of two ZA3's I had qualified for a useful £60 discount which is, of course, time limited to 27th Dec.

Your thoughts please.
Regards.
Phil.

Ps. The ability of the ZA3 to retain it's volume level setting through a switch off and back on cycle is a great piece of functionality that should greatly enhance usability. Particularly after matching the outputs of two units in mono mode.
 
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.
internals.jpeg


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:

Features​

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:
ZA3-FR.png
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.

trigger-input.jpg


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
Standby0.9w
Triggered7.0w
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

Summary​

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.
 
Hello friend,

Sorry for the inconvenience. It's true that ZA3 uses an on/off switch integral to the volume control. When the power is cut off, we need to long press the knob to power it on. In this case, it could be a problem when using a smart plug.😢

We've marked down your concern and we'll probably change the switch mode, like moving the power switch to the toggle lever.
It's true that it's a problem to need to press the volume button...
With a plug connected or in use as a power amp on an amp / preamp that has an electrical output, it won't work, it's a real shame...
 
I would like to share also my opinion about the ZA3.

I like very much how the amplifier looks like and how you can feel it in your hands. The case seems to be very solid and give you a good impression and the effort that Fosi has put in the design is also quite clear with the choice of colors (I love the orange knob) and the side holes which, in addition to being very useful for heat dissipation, are very attractive due to the presence of the net with the same color of the knob.

Fosi Audio ZA3 is equipped with high-quality components like German Wima capacitors, Japanese NCC and ELNA capacitors, and Japanese Sumida inductors.

What about how this small amplifier sounds to me? My setup was a Pro-Ject turntable with integrated phono stage + Fosi ZA3 + Dali Oberon 5 speakers (6 Ω impedance). The turntable was connected to the amplifier via RCA cables.

The sound is warm and full with nice low frequencies, for sure due to the neutral frequency response showed by jeromeof, and the soundstage is large and detailed. You can feel the position of each instrument and musicians in front and behind the line of the speakers and this makes the listen experience more emotional, clean and vivid. I compared the same set up (turntable + speakers) with my Fosi Audio BT20A Pro, and I can easily say that the ZA3 sounds better and punchier.

At the end, what I liked:
  • of course how the music goes out of the speakers in terms of imaging and separation, it’s crazy how good this amp sounds for the price.
  • the design of this brand new Fosi amplifier.
  • The 12V trigger input, also if I didn’t test it but it is for sure very useful to have.
  • The possibility to change the op-amps very easily, so you can have your personal signature with your own amplifier.
I agree with previous comments about something to modify on this amplifier. For instance, the mono/stereo switch could be placed on the back or underneath (you do not need often to switch from mono to stereo, or vice versa, once you have defined your setup). Instead, I should appreciated that this switch could be used for the power on/off, to avoid frequent accidental change of volume setting especially in mono mode.
 
just a v quick one to say how much I love this. Was going to swap my WiiM Pro Plus for a WiiM amp but saw the various discussions, kept the streamer and brought this in. I'm no audiophile but like to try and get the best with what I can afford. It is wonderful. Just have set up with the WiiM Pro Plus with a Denon Prime Go set of decks coming in through the line in of that and the ZA3 and a wire for the trigger. Faultless. I love the little click when the trigger turns the amp on and off. The sound is off the scale.
 
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.
internals.jpeg


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:

Features​

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:
ZA3-FR.png
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.

trigger-input.jpg


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
Standby0.9w
Triggered7.0w
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

Summary​

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.
Hello jeromeof,
,
About the 12V trigger out/in connection between WIIM pro plus and Fosi ZA3, ..as I can see from your pic, on the WIIM side you have 2 pole 2,5mm jack. Do you have on the Fosi side 2 pole 3,5mm jack or is it 3 pole (stereo) jack?

Borislav
 
Last edited:
Hello jeromeof,
,
About the 12V trigger out/in connection between WIIM pro plus and Fosi ZA3, ..as I can see from your pic, on the WIIM side you have 2 pole 2,5mm jack. Do you have on the Fosi side 2 pole 3,5mm jack or is it 3 pole (stereo) jack?

Borislav
A 2 pole 3.5mm on the Fosi side - I found I had to 'fiddle' with it a bit to get it working but once connected it worked well
 
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