Fosi Audio ZA3 Amplifier Review

[AudioSceptic]

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

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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:
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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/

It's a shame that they don't put the PS in a nice matching case, one you would see and not hide away.

 

[Talisman]

It's a shame that they don't put the PS in a nice matching case, one you would see and not hide away.

A useless waste of money in an amplifier that makes low cost its strong point, I don't know why so many people are so annoyed by external power supplies, for me they are fanatical because they can be hidden anywhere and do not take up space on the main surfaces, as well as reducing the possibility of interfering with the performance of the amplifier

 

[Ajax]

I can't understand the filtered sub out. An unfiltered pre out is more flexible, subwoofers have their own filter anyway.

According to the review below the sub out does not place a high pass filter on the mains, which is unfortunate as it would have allowed you to run the mains above a certain crossover, and the sub below, and therefore take pressure off this little amp, and make it a great buy for a second system.

Even a fixed crossover at around say 70hz would work really well for most speakers.

Fosi Audio ZA3 - Initial Review

In this review, we will get into the details of the new Fosi Audio ZA3 Amplifier - the latest TPA3255 amplifier Fosi Audio. I received my via their...

www.superbestaudiofriends.org

 

[Barry_Sound]

Guys, I trade your old A/B high end amps for this Fosi thing anytime. They sound the same anyway, right? Just let me know when you want to make the trade.

 

[somebodyelse]

It’s not a bridging switch. It’s just a single channel driven- suck less power from the PSU mode…

Please, Make it clear.

"Mono" on ZA3 means BTL, PBTL or just one-channel possible?

It is very confusing.

From my understanding the mono mode just shuts down one channel, resulting in more power to the other one with the same PSU. No bridging is done.

A TPA3255 configured for stereo operation is already bridged. The operating modes can be seen in Table 1 of TI's datasheet.
As shown in post #34 the documentation says that in mono mode the minimum load is 2R. This strongly suggests mono mode is PBTL - using both channels in parallel. The related 1xBTL mode (single side driven, other side not switching which should reduce waste heat a bit) wouldn't change the minimum load.

 

[DSJR]

Thank you for your review Amir.
_____


Quite important with an amp that is not load dependent, has good FR (the most important criterion?). But okay, if you want to color the sound, why not.

What if a speaker exhibits, say, 15-20 Ohms at 8-10 kHz, what would this amps FR look like?

Hmm - You might still be able to hear +/-0.5dB at 15kHz and +1dB at 20kHz, but the former frequency was lost to me decades ago and I don't think my hearing even as a teenager ever went much past 18kHz, which I could definitely perceive at age 15 on the science lab's headphones such as they were

 

[DanielT]

Hmm - You might still be able to hear +/-0.5dB at 15kHz and +1dB at 20kHz, but the former frequency was lost to me decades ago and I don't think my hearing even as a teenager ever went much past 18kHz, which I could definitely perceive at age 15 on the science lab's headphones such as they were

It was good that you pointed that out. You can test how high up in frequency you can hear and then take it from that, how to approach this amplifier's FR that is.
I think I can hear up to 15 kHz, but it's been a few years since I tested. Probably 14kHz now.

Okay,
+/-0.5dB at 15kHz and +1dB at 20kHz is at 8 Ohms, but if the speaker presents higher Ohms, what happens? Even more deviation from FR? I do not know.

 

[restorer-john]

This strongly suggests mono mode is PBTL - using both channels in parallel.

Not in my book, but it could be I guess. It would require a few relays in the amp, to disconnect and reconnect the outputs from each channel to a common pair. Notice the output is just one set, not two.

I'd lay my money on them simply shorting the input to one channel and calling the whole thing "mono". Look at the specs, they are hardly changed.

And parallel BTL is a misnomer.

 

[Yorkshire Mouth]

Looks good.

Astonishing that they can do this at that price.

 

[restorer-john]

Astonishing that they can do this at that price.

What's astonishing exactly? A chip amp, in a tiny aluminium can, with an off-the-shelf SMPS. I don't see anything remotely astonishing about it. Personally, I think it's way overpriced for what it is (or isn't)

How grown men can get excited about an "amplifier" lacking pretty much everything that makes an amplifier remotely useful is beyond me.

One set of speakers- not switchable
No headphone socket
No tone controls
No filters
No loudness
No tone defeat
No signal routing options
No processor loops
No remote control
No muting
No phono stage
Only two inputs- LOL what a joke.

All of these things (except remote) were standard on ~USD$100 integrated amplifiers in the 70s/80s/90s and into the 2000s.

 

[T&T]

I own the Fosi V3 and Aiyima07 Max both with 48v power supply...using geshelli akm4499 and wiim pro....Aiyima07 Max sound Amazing with muses 02 and I prefer over V3 so V3 was sold....I know measure measure measure but for me is how sounds.

 

[somebodyelse]

Not in my book, but it could be I guess. It would require a few relays in the amp, to disconnect and reconnect the outputs from each channel to a common pair. Notice the output is just one set, not two.

It would require more components, but I don't see how else the allowed load would change. Unless their manual is wrong, which I'll grant isn't unheard of...

I'd lay my money on them simply shorting the input to one channel and calling the whole thing "mono". Look at the specs, they are hardly changed.

Could be. But then why is the distortion performance so much worse in mono than stereo? Perhaps @Fosi Audio can tell us exactly what they've done.

And parallel BTL is a misnomer.

Perhaps, but that's the terminology TI used in the datasheet. There's already more than enough confusion without adding to it by mixing terminology.

 

[Deleted member 48726]

What's astonishing exactly? A chip amp, in a tiny aluminium can, with an off-the-shelf SMPS. I don't see anything remotely astonishing about it. Personally, I think it's way overpriced for what it is (or isn't)

How grown men can get excited about an "amplifier" lacking pretty much everything that makes an amplifier remotely useful is beyond me.

One set of speakers- not switchable
No headphone socket
No tone controls
No filters
No loudness
No tone defeat
No signal routing options
No processor loops
No remote control
No muting
No phono stage
Only two inputs- LOL what a joke.

All of these things (except remote) were standard on ~USD$100 integrated amplifiers in the 70s/80s/90s and into the 2000s.

If you compare like that, true.
I tend to look at them like tiny load dependent power amplifiers with a huge power brick of questionable quality. Add to that, that a new model come out with shorter intervals than Samsung spit out smartphones.

But I shall not say more to avoid being schooled by the fans.

 

[Bruce Morgen]

All of these things (except remote) were standard on ~USD$100 integrated amplifiers in the 70s/80s/90s and into the 2000s.

The thing is, this is not an integrated amplifier -- it's a power amplifier with a few atypical features. My old Kenwood KM-8002 was like that, as was the McIntosh pictured earlier in this thread -- power amps with a couple of "bells & whistles" you won't find in your dad's Dynaco ST-70 because all the features you're kvetching about belong in a preamp, assuming the use case of the moment needs that stuff. I'm not tooting the horn for this product and I agree $150 USD is way too much -- with the 48V power brick, it's nearly twice the price of an Aiyima A07 + a similar PSU, and IMO it won't perform significantly better in most applications. Even though it's a little quieter and can deliver more power, there are relatively few low-priced systems that can really benefit from those technical improvements. As for $100 "entry-level" integrated amps from back in the day, IIRC they were pretty much crap -- just good enough to avoid staining the reputations of their makers and way short in power and S/N compared to today's sub-$100 TPA3255 chip amps.

 

[somebodyelse]

All of these things (except remote) were standard on ~USD$100 integrated amplifiers in the 70s/80s/90s and into the 2000s.

You had those things back then in a preamp or integrated because you had multiple sources, so it made sense to put the eq there. Now a lot of people only have one source - a streamer - with most of that functionality built in. What they need is closer to a power amp, hence things like this. A more relevant complaint is that it doesn't have bluetooth for people who only use their phone as a source.
Inflation has made your price comparison somewhat meaningless. In 1979 a NAD 3020 was £71, about £362 today, and gave you ~20W.

 

[DTTOM37]

It's harmless and allows use of a passive sub driven by a separate amp that doesn't have its own low-pass filter -- e.g. a second ZA3 in mono mode.

Am I mistaken that I am thinking (looking at the graphs) that the ZA3 in mono mode may be an excellent (and cheap) low-end amplifier for an active 2-way solution with an x-over at 250hz? What could go wrong driving two 15" bass modules in parallel at 4 Ohms and more than 90db sensivity per channel?
The rest of the audible spectrum is managed by a PA5 II.

 

[Power Pop 23]

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.

I can happily live with the volume control set to maximum on my ZA3. AFAIK, manufacturers like Topping, SMSL, Fosi, and their related brands do not offer a solid-state amplifier without a volume control (the Topping LA90 series amplifiers have a volume bypass switch). I find that surprising, given the breadth of audio electronics gear they offer for sale.

 

[RCL162]

I want a power amp...

 

[Yorkshire Mouth]

What's astonishing exactly? A chip amp, in a tiny aluminium can, with an off-the-shelf SMPS. I don't see anything remotely astonishing about it. Personally, I think it's way overpriced for what it is (or isn't)

How grown men can get excited about an "amplifier" lacking pretty much everything that makes an amplifier remotely useful is beyond me.

One set of speakers- not switchable
No headphone socket
No tone controls
No filters
No loudness
No tone defeat
No signal routing options
No processor loops
No remote control
No muting
No phono stage
Only two inputs- LOL what a joke.

All of these things (except remote) were standard on ~USD$100 integrated amplifiers in the 70s/80s/90s and into the 2000s.

Astonishing, in the meaning that I’ve seen so much less for so much more over the decades.

 

[Power Pop 23]

FYI - for those members who already own a performant power supply unit.......


Fosi Audio offers the option of ordering a ZA3 amplifier without a power supply unit for $109.99

Fosi Audio ZA3 Balanced Stereo Amplifier Home Audio 2CH Mono Amp with TPA3255 Chip

This new generation mini amplifier offers both stereo and mono modes, adapts flexibly to your diverse needs, allowing seamless mode switching.

fosiaudio.com