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Fosi Audio ZA3 Amplifier Review

Rate this amplifier:

  • 1. Poor (headless panther)

    Votes: 11 3.1%
  • 2. Not terrible (postman panther)

    Votes: 54 15.2%
  • 3. Fine (happy panther)

    Votes: 211 59.4%
  • 4. Great (golfing panther)

    Votes: 79 22.3%

  • Total voters
    355
When you're looking for ZA3 info and that information buried in a V3 review, a typical person isn't going to find it. I edited my post with a disclaimer that I was wrong. SORRY.
ASR is an open forum… but I found there is an unwritten expectation for members to do *some* research before posting anything.

You bought your opamps on eBay. They may or may not be fake… regardless, unless you have a solid measurement toolchain, I bet you are going to hear differences! :p
 
Agreed. It'd easily be a first choice for me if I were just getting started as a young audio enthusiast seeking to assemble a music system. It's pretty astonishing what one can buy in the amplifier and DAC category these days for very little. The price vs performance ratio is astronomical.
My audio journey began in H.S. when as a junior I purchased an HK receiver, EPI 100 speakers and BIC turntable. I think I got the receiver and TT from the audio room section in the back of a Sam Goody store. That was 1974 and the receiver was a close-out and did not come with the intended wooden casing, so it was just an ugly metal. It may have been $150 or so. The BIC turntable at the time was a popular entry level choice. I can't recall the price but probably a bit over $100. And I think the EPI 100s were $99 each at the time. So in 2024, so 50 years later you can get far superior and transparent equipment for the same or less than it cost in 1974! There are very few consumer items one can make such a claim about.

I see the old TT on sale on eBay for $170! Yikes!

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This is a review and detailed measurements of the Fosi Audio ZA3 stereo amplifier with balanced XLR inputs. It was sent to me by the company and costs US $149.99 with 48 volt power supply.
View attachment 348770
The amplifier has really dressed up from its earlier origins of common enclosures in budget class amplifiers. It looks a lot more "beefy" and substantial. It also looks a lot better with nice series of holes on the sides where copper color is seen through it. Maybe due to these reasons the amplifier kept its cool for the entire test.

On controls, you push the volume control in to turn it on and off. Turning on causes an orange LED to light. Turning it off causes a delay in the light going out even though the output shuts off. Not an issue if you are listening to it but in testing, I am not so it was a bit confusing at first.

There is a misnamed "mono" vs "stereo" switch. Mono doesn't make both channels the same but rather, shuts off one channel allowing for more power in the channel that is left running. The other button is key in book which is support for balanced XLR input to help in avoiding ground loops:

View attachment 348772

The connectors are combo so you can either use XLR or 1/4 inch. There is still RCA inputs of course and support is provided for a filtered, and volume controlled subwoofer output. Finally we have trigger input so you can turn the amplifier on automatically if you power on your upstream product and it has trigger out, and vice versa.

You may have noticed that it has taken a bit of time to get this review out. I received a sample a while back. Upon testing, I noticed that the gain was substantially increased due to user feedback for louder volume. This was a regression from V3 amplifier and as a result, caused the ZA3 measured performance to drop by a a few dBs. I provided the feedback to Fosi and they made the decision to back out the extra gain and shipped me a new sample a couple of weeks ago. I am assuming newer models being sold are what I have tested but they would have to confirm.

Fosi Audio ZA3 Measurements
Let's start with our dashboard using XLR input:
View attachment 348774
This is the level of performance I expect. Using RCA, you get similar performance but gain is a bit higher:
View attachment 348775

This nicely lands ZA3 above average of all amplifiers tested regardless of price and almost next to its V3 sibbling:
View attachment 348776

View attachment 348777

Continuing with XLR input testing, noise performance is excellent especially for the class:
View attachment 348778
It takes around 1.2 volts to cause clipping which is well within the output level of just about any source.

Frequency response shows load impedance dependency which is part and parcel of class D amplifiers at this price point and lower:
View attachment 348779
This means depending on your speaker impedance, high frequencies may be exaggerated a bit.

I measured subwoofer out and it seems good enough:
View attachment 348780
Note that I was driving it from XLR input and it still routed that to the RCA sub out.

Crosstalk is very good:
View attachment 348781

Using balanced input nicely eliminated low frequency spikes in low frequencies:
View attachment 348782

Distortion does increase at higher frequencies though so 19+20 kHz intermodulation doesn't impress:
View attachment 348783

Inclusion of beefy 48 volt power supply pays dividends in available power:
View attachment 348784
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Running power sweeps at different frequencies shows again the issue with jump in distortion at higher frequencies:
View attachment 348787
Optimization at lower frequencies is impressive though with ultra smooth graphs at or below 1 kHz.

"Mono" Mode Amplifier Measurements
I switched to Mono and measured the dashboard again:
View attachment 348788
Distortion is increased causing SINAD to drop by some 13 dB. In exchange for that, you do get more power:

View attachment 348789

Other Amplifier Measurements
ZA3 was stable on power up:
View attachment 348790

Pop noise was slightly reduced compared to V3:
View attachment 348791
This could be sample to sample variation though.

Conclusions
It is nice to see this class of amplification with its bargain prices come in much more serious and substantial packaging while still remaining small and desktop oriented. Performance is as great as ever and inclusion of features such as balanced input is very much welcome. Load dependency remains and solving that would be the next logical feature request.

I am going to recommend the Fosi Audio ZA3 amplifier.

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As always, questions, comments, recommendations, etc. are welcome.

Any donations are much appreciated using: https://www.audiosciencereview.com/forum/index.php?threads/how-to-support-audio-science-review.8150/
@amirm This is not specific to this particular amp but in nearly every test, I see this increasing slope below 100Hz - ish with all measurements:

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I understand the high frequency content is white noise but why is there this increasing noise level at low frequencies and why does every device tested have it?
 
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@amirm This is not specific to this particular amp but in nearly every test, I see this increasing slope below 100Hz - ish with all measurements:

View attachment 349306

I understand the high frequency content is white noise but why is there this increasing noise level at low frequencies and why do every device have it?
It is hard to say what the nature of it is. It is not the analyzer though as high performance products don't have it:

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But why would you ask them to reduce gain, I'm using BE with 48V and it's not enough in HT use. Low gain.
 
I explained that in the review. Even with balanced input, it only needs 1.2 volts to reach clipping. The stock version has some 32 dB of gain. That is way too excessive.

Note that I did not tell them to do anything. I just showed them the measurements and explained the reasoning for regression.
 
It appears Fosi Audio is charging $129.99 for the ZA3 with a 32 volt, 5 ampere power supply and $149.99 for a ZA3 with a 48 volt, 5 ampere power supply

It costs $175.99 when I visit the website here in Germany:
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FYI, if buying from Europe :

 
It's the difference in VAT between EU countries. Due to competition avoidance laws, the VAT applied in EU e-shops is the one you shop from.
In Greece for example there's a tiny 24% @!#%@&^&
 
I explained that in the review. Even with balanced input, it only needs 1.2 volts to reach clipping. The stock version has some 32 dB of gain. That is way too excessive.

Note that I did not tell them to do anything. I just showed them the measurements and explained the reasoning for regression.
Just to be 100% clear, this is after they turned the gain down? So it could have clipped on a 1v dongle previously? My keyboard has 4v on its balanced output. This could make my life with this guy difficult.
 
Hello all, and thank you @amirm for this review.

It looks like the ZA3 is essentially an improved or expanded V3 with more functionality (better cooling, 2 inputs, filtered subwoofer output, trigger input, and 1 channel mode) and what I consider a step up in design. Great!

@Fosi Audio : could you please tell us more about the different products reviewed here? Was the first version sent to Amir and ASR a prototype with higher gain?
 
I'm a bit worried about the distortion rise between 1khz and 5khz. Would we expect this to have audible hiss if the volume knob is maxed out?
 
While I see your point, the volume control here gives you variable gain settings. In my testing I just set it to max and ran all the tests.
So a question… I understand a gain control, but will there presumably be a voltage input where the input section will effectively hit a ceiling and you can clip it if you send too much voltage in?
 
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