Fosi Audio ZA3 Amplifier Review

[HalSF]

Thanks for the replies. Those reasons offered for the tilt toward the V3 monos— PFFB, better performance with some harder-to-drive speakers — seem valid but I'm not sure I see them as widespread factors that explain V3 mania vs. tepid ZA3 enthusiasm. (Also not sure I'm understanding the implication that the ZA3 is *not* "neutral/flat through the audible band," but maybe I missed that is Amir's testing?)

I'm still not really sure what the explanation for the discrepancy in interest may be — 160 pages of discussion in the V3 review thread vs. 43 here for the ZA3 review thread.

 

[gigantic]

Thanks for the replies. Those reasons offered for the tilt toward the V3 monos— PFFB, better performance with some harder-to-drive speakers — seem valid but I'm not sure I see them as widespread factors that explain V3 mania vs. tepid ZA3 enthusiasm. (Also not sure I'm understanding the implication that the ZA3 is *not* "neutral/flat through the audible band," but maybe I missed that is Amir's testing?)

I'm still not really sure what the explanation for the discrepancy in interest may be — 160 pages of discussion in the V3 review thread vs. 43 here for the ZA3 review thread.

I am running a quartet of ZA3 to drive the woofers and tweeters of a pair of 106db sensitive 3-way horns and am exceptionally pleased with their performance. They have Burson V7 Classic and V7 Vivid op amps in them. They’re quiet. They sound great. They drive my admittedly easy to drive, 8 ohm drivers with aplomb. There’s not much more to be said.

 

[JRowland]

I'm still not really sure what the explanation for the discrepancy in interest may be — 160 pages of discussion in the V3 review thread vs. 43 here for the ZA3 review thread.

Owners who nitpick and/or argue less perhaps?

 

[SoySalsaPicante]

...Also not sure I'm understanding the implication that the ZA3 is *not* "neutral/flat through the audible band,"...

4ohm speakers will sound darker to the tune of 0.5dB, 8ohm speakers will be brighter/more airy or have more sparkle, possibly excessively, depending on if a full 1dB is harsh sounding to you.


While on V3 Mono, there was a 0.5dB rise at most at 20KHz:

All that said, WiiM Amp Ultra trumps both Fosi amps:

 

[Power Pop 23]

View attachment 504719

4ohm speakers will sound darker to the tune of 0.5dB, 8ohm speakers will be brighter/more airy or have more sparkle, possibly excessively, depending on if a full 1dB is harsh sounding to you.


While on V3 Mono, there was a 0.5dB rise at most at 20KHz:
View attachment 504725


All that said, WiiM Amp Ultra trumps both Fosi amps:
View attachment 504728

Agreed.

For my aged ears, I consider the effect of speaker/load dependency up to a frequency of 15,000 Hz.

I appreciate the convenience of the ZA3's trigger input and until the introduction of the Topping Mini 300 at $139, I believe the Fosi Audio ZA3 was the lowest-cost amplifier to offer a 12 volt trigger input.

 

[obsessive9119]

Agreed.

For my aged ears, I consider the effect of speaker/load dependency up to a frequency of 15,000 Hz.

I appreciate the convenience of the ZA3's trigger input and until the introduction of the Topping Mini 300 at $139, I believe the Fosi Audio ZA3 was the lowest-cost amplifier to offer a 12 volt trigger input.

This was why I went with the ZA3 too - my speakers roll off a bit at the very high end, and I doubt I could hear the nonlinearity anyway. The power difference is minor and I like the volume control as an option.

Every now and then I’m still tempted to buy V3 minis just because they’re something cool about a couple of tiny monoblocks.

 

[somebodyelse]

V3 Monos have a design that keeps frequency response neutral/flat through the audible band. The ZA3 does not have that same circuitry (PFFB as pointed out by gigantic), so depending on the speakers attached to the ZA3, they may have elevated or rolled off high frequency response.

It's not just the top end of the HF response - see Erin's test with dummy loads representative of speakers rather than pure resistance and you'll see altered frequency response down to ~2kHz.
https://www.erinsaudiocorner.com/electronics/fosi_za3/

 

[Pulkass]

Manufacturer Specifications:


View attachment 348848
View attachment 348849

Used as a power amp--volume all the way up, connected to a Fosi Audio ZP3, strong noise if no signal is present, sputtering-motor like noise! If not connected to the pre amp there is no noise at all !!!!!

 

[obsessive9119]

Used as a power amp--volume all the way up, connected to a Fosi Audio ZP3, strong noise if no signal is present, sputtering-motor like noise! If not connected to the pre amp there is no noise at all !!!!!

Have you tried a different source?

 

[antcollinet]

Used as a power amp--volume all the way up, connected to a Fosi Audio ZP3, strong noise if no signal is present, sputtering-motor like noise! If not connected to the pre amp there is no noise at all !!!!!

Almost certainly a ground loop. A system problem rather than a component problem. What is driving the preamp?

 

[Pulkass]

Have you tried a different source?

The system is : Dac - USB fed from PC. Pre amp. Power Amp. It s just for the PC. System 3 of my abose.

 

[komhst]

The system is : Dac - USB fed from PC. Pre amp. Power Amp. It s just for the PC. System 3 of my abose.

Is the PC laptop or desktop?

 

[Pulkass]

A mini PC. Installed yesterday. Ryzen 7 6800. Got rid of the huge, noisy, warm, classical tower PC.

 

[komhst]

Does the power cord have two or three terminals? Is it grounded or not?

 

[Pulkass]

Does the power cord have two or three terminals? Is it grounded or not?

Three terminals. In the pre amp.

 

[J-Mo]

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
View attachment 348785
View attachment 348786

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

+1
Nice exterior design and power. Otherwise not superbly interesting

Has anyone tested the output impedance?

 

[staticV3]

Has anyone tested the output impedance?

Yes: https://www.erinsaudiocorner.com/electronics/fosi_za3/

 

[gwing]

A mini PC. Installed yesterday. Ryzen 7 6800. Got rid of the huge, noisy, warm, classical tower PC.

Try just the pre-amp and Fosi with the PC disconnected to establish which of these the interference is coming from.
Also - are you using XLR or RCA inputs?

 

[Pulkass]

Try just the pre-amp and Fosi with the PC disconnected to establish which of these the interference is coming from.
Also - are you using XLR or RCA inputs?

I m a balanced circuit and cables maniac

 

[gwing]

I m a balanced circuit and cables maniac

So looking more and more likely that you have a ground loop issue to fix.