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Fosi Audio ZA3 Amplifier Review

Rate this amplifier:

  • 1. Poor (headless panther)

    Votes: 9 2.7%
  • 2. Not terrible (postman panther)

    Votes: 52 15.5%
  • 3. Fine (happy panther)

    Votes: 203 60.6%
  • 4. Great (golfing panther)

    Votes: 71 21.2%

  • Total voters
    335

amirm

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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.
Fosi Audio Stereo Class D Amplifier ZA3 balanced XLR review.jpg

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:

Fosi Audio Stereo Class D Amplifier ZA3 balanced XLR back panel subwoofer out review.jpg


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:
Fosi Audio Stereo Class D Amplifier ZA3 Measurements.png

This is the level of performance I expect. Using RCA, you get similar performance but gain is a bit higher:
Fosi Audio Stereo Class D Amplifier ZA3 RCA Measurements.png


This nicely lands ZA3 above average of all amplifiers tested regardless of price and almost next to its V3 sibbling:
best class d cheap amplifier review.png


best class d cheap amplifier zoom review.png


Continuing with XLR input testing, noise performance is excellent especially for the class:
Fosi Audio Stereo Class D Amplifier ZA3 SNR Measurements.png

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:
Fosi Audio Stereo Class D Amplifier ZA3 frequency response Measurements.png

This means depending on your speaker impedance, high frequencies may be exaggerated a bit.

I measured subwoofer out and it seems good enough:
Fosi Audio Stereo Class D Amplifier ZA3 subwoofer frequency response Measurements.png

Note that I was driving it from XLR input and it still routed that to the RCA sub out.

Crosstalk is very good:
Fosi Audio Stereo Class D Amplifier ZA3 Crosstalk Measurements.png


Using balanced input nicely eliminated low frequency spikes in low frequencies:
Fosi Audio Stereo Class D Amplifier ZA3 Multitone Measurements.png


Distortion does increase at higher frequencies though so 19+20 kHz intermodulation doesn't impress:
Fosi Audio Stereo Class D Amplifier ZA3 19 20 kHz Measurements.png


Inclusion of beefy 48 volt power supply pays dividends in available power:
Fosi Audio Stereo Class D Amplifier ZA3 balanced power 4 ohm Measurements.png

Fosi Audio Stereo Class D Amplifier ZA3 balanced max and peak power 4 ohm Measurements.png

Fosi Audio Stereo Class D Amplifier ZA3 balanced power 8 ohm Measurements.png


Running power sweeps at different frequencies shows again the issue with jump in distortion at higher frequencies:
Fosi Audio Stereo Class D Amplifier ZA3 balanced power 4 ohm vs frequency vs distortion Measur...png

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:
Fosi Audio Stereo Class D Amplifier ZA3 Mono Mode Measurements.png

Distortion is increased causing SINAD to drop by some 13 dB. In exchange for that, you do get more power:

Fosi Audio Stereo Class D Amplifier ZA3 Mono Mode Power 4 ohm Measurements.png


Other Amplifier Measurements
ZA3 was stable on power up:
Fosi Audio Stereo Class D Amplifier ZA3 Warm up Measurements.png


Pop noise was slightly reduced compared to V3:
Fosi Audio Stereo Class D Amplifier ZA3 power on off noise Measurements.png

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.

------------
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/
 
Last edited:

_thelaughingman

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It's finally up!
 
Last edited:

Bleib

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Load dependency remains and solving that would be the next logical feature request.
+1
Nice exterior design and power. Otherwise not superbly interesting
 

iLoveCats

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I just hooked mine up. Been waiting for over a month. Replacing a PA5. First impression is it sounds a tad dark? I like it. The gain is higher than the PA5 because I barely have to turn up my preamp. Really nice case. I'll run it a couple weeks and if it's ok I'll buy another for monoblocks.
 

Talisman

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Thanks Amir, I was just wondering why the review was taking so long.
Frankly, this product has some points in favor but some against it. The xlr input and the trigger are two great additional features, as is the nice and efficient enclosure, however the mono is not true mono, and the 13 db of sinad lost is a bit disappointing, especially given a boost certainly not exceptional in power. At present, for those who don't need the particular features of this model, I would still suggest aiming for the V3.
But in reality Fosi is getting used to it well and the rumors of a project with PFFB implementation intrigue me a lot, I will await future projects with extreme interest, I consider this as a hybrid which at the moment doesn't make me want to open my wallet.
 

dogmamann

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I just hooked mine up. Been waiting for over a month. Replacing a PA5. First impression is it sounds a tad dark? I like it. The gain is higher than the PA5 because I barely have to turn up my preamp. Really nice case. I'll run it a couple weeks and if it's ok I'll buy another for monoblocks.
What is dark?
 
OP
amirm

amirm

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In US, where do you buy it at that price?
I have only seen non-XLR version?
I was going by the Fosi website product page with that pricing. It says it is not available yet until next month.
 

Mikig

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some considerations:

1) I think there are very few amps with balanced inputs at this price

2) the price/performance factor is scary. It would probably put it at the top of any ranking

3) I had a V3, taken for testing, and I admit that it was a really good amplifier, not at all intimidated even with quite large speakers. So this shouldn't be any less.

4) the only note: the system proposed by Fosi which makes it usable also as both a stereo and mono power amplifier, it seems fun, to experiment and play a bit, but leaves me a little perplexed: two or three potentiometers on the same line seem too many to me. I am afraid that the signal may have deteriorated in some way. I would prefer a pure power amp therefore without controls.

5) congratulations to Fosi for this line of products, which is essentially spot on for the price.
 

phoenixdogfan

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So the major improvements over the V3 are the XLR inputs and the mono-bridging switch. Again, seems like a really good deal. $130 USD gets you performance which equals or betters a great many "high end" amps being sold even today, XLR input, and the option to bridge to mono.

It is basically an Aiyima A7 or a V3 with those two added features. It also comes with the 5amp, 48v power supply, so need to upgrade there.

For anyone just starting out, the best thing is to max out on the speakers, and buy these kind of electronics. An amp like this could deliver years of trouble free high quality performance driving those Kefs, Revels, Ascends, Buchardts, and Wharfdales. You may forget how little you paid and just enjoy the music.
 
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amirm

amirm

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+1 to that!
Volume should come out of the DAC.
Power amp should have zero volume control, and (at worst) MAYBE three gain settings (lo / med / hi)
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.
 
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amirm

amirm

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The table shows the Wiim amp 88 SINAD. When has the Wiim amp been tested in ASR and where can I find the test?
It is in the process. I found an issue with my sample and they sent me another one. I hope to get that done very soon now.
 

Power Pop 23

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I was going by the Fosi website product page with that pricing. It says it is not available yet until next month.

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

 
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