Fosi Audio ZA3 Amplifier Review

[musicforcities]

Thanks on behalf of everyone for going above and beyond in alerting fosi about the early issue with the distortion and gain.

The power trigger and sub out are great additions.

The trigger especially allows these little amps to easily integrate into home audio distribution systems. Fossi should make a rack mount bracket/shelf with two or three slots for the amp with a space for the power bricks on the side. Heck you could just use a standard shelf and some Velcro tape on the amps and power bricks to achieve similar neatness and security. Or just buy the amp and use a different single power supply that can give 48v at 10amps for two amps. Such a solution makes more sense that Topping’s rack mount sub-line in that you could get two amps in the same space. Especially since one can bridge the amps.

The decreased performance when bridged is a serious bummer however as that would be the other main draw. the performance drop would be less of an issue in distribution systems and in ceiling/wall speakers, or surrounds however, vs the advantages of the increased power.

For now, 3e audio remains the performance champ of these 3255 amps. If you are ready for some diy.

 

[Ajax]

I think the main issue is a dearth of inexpensive, decent-to-good quality LR4 active stereo (or stereo to sub-out) crossover boxes with volume control. Without that, we're expecting amps to have to handle basically everything needed to control a 2.1 setup, when it should be something discrete and upstream.

Like the 2x4HD, except that it's still not that "cheap" and some people don't really need the DSP it offers. And no volume knob (but does have a remote). And doesn't come in balanced, FWIW.

Yes, you can add another box, but I'm not sure if I follow your logic?

Fosi stated that they chose to improve their product by adding several features:

"Based on the V3, we improved the heat dissipation design, added balanced input, and introduced the ability to switch between stereo and mono modes, along with adding sub-out and trigger-in ports. These features were all highly requested by users."

My point is that if you are going to add features then make them real features and functional, not window dressing, which the sub out currently is without properly integrated cross overs/filters. These filters will greatly reduce the work load on both the amp and main speakers by directing low frequencies away from them to the sub, which is designed for reproducing them.

A lot of audiophiles use 2.1 systems and I'm surprised that more front end products, eg integrated amps, pre amps, DACs etc, don't provide such an obvious improvement, one which has already been incorporated into subs themselves for a very long time.

 

[musicforcities]

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.

Unless the pot they use essentially bypasses the trace when turned to max.

 

[musicforcities]

Yes, you can add another box, but I'm not sure if I follow your logic?

Fosi stated that they chose to improve their product by adding several features:

"Based on the V3, we improved the heat dissipation design, added balanced input, and introduced the ability to switch between stereo and mono modes, along with adding sub-out and trigger-in ports. These features were all highly requested by users."

My point is that if you are going to add features then make them real features and functional, not window dressing, which the sub out currently is without properly integrated cross overs/filters. These filters will greatly reduce the work load on both the amp and main speakers by directing low frequencies away from them to the sub, which is designed for reproducing them.

A lot of audiophiles use 2.1 systems and I'm surprised that more front end products, eg integrated amps, pre amps, DACs etc, don't provide such an obvious improvement, one which has already been incorporated into subs themselves for a very long time.

Indeed, one can get some of the advantages of stand mount speakers but mitigate

I would never buy an amp with an external power brick. It's as big as the amp and you have to put it somewhere. It would be interesting to know how hot that external brick gets after an hour of use. Made in China Fire Hazard? I would certainly unplug the power brick when not in use.

their recent power supplies have been pretty well made. And run warm but not hot. The hottest power brick I have ever felt was for the Xbox 360: massive and far too hot.

I get tired of dealing with all these power bricks too but the amps brick is just another to add to the pile. We live in the age of power bricks.

I suppose There are a couple possible advantages or external power bricks, depending on ones set up and the equipment:

1) you can put the bricks on an enclosed or not visible location

2)if power supply fails, it is super simple to replace.

3) one can use a single ps with increased amp rating to power two amps.

4) one can more easily keep 120/240v ac power lines far away from line level interconnects etc.

5) if the ac power cord is detachable from the brick, you can swap it out with a short one. Less messy and less looping ac cords. It’s hard to avoid power bricks these days.

6) lower cost to manufacture the amp. One can get a brick certified and use it to power many different models of amps, and update amps and make new models with less certification hoops. Up to a point. 48v is not nothing.

7) plastic and double insulated power bricks may help with ground loop issues and in any case make it easier for manufactures to meet safety standards in expensively.

8) it’s also often easier to shield and isolate switching ps when it’s in a brick. take apart and old brick from an ibm laptop (when they made them). Plastic case, metal shield, then another layer of plastic wrapping the pcb and components. Shield grounded to safety earth pin, which is otherwise not used and needed due to double insulated construction.

 

[musicforcities]

Yes, you can add another box, but I'm not sure if I follow your logic?

Fosi stated that they chose to improve their product by adding several features:

"Based on the V3, we improved the heat dissipation design, added balanced input, and introduced the ability to switch between stereo and mono modes, along with adding sub-out and trigger-in ports. These features were all highly requested by users."

My point is that if you are going to add features then make them real features and functional, not window dressing, which the sub out currently is without properly integrated cross overs/filters. These filters will greatly reduce the work load on both the amp and main speakers by directing low frequencies away from them to the sub, which is designed for reproducing them.

A lot of audiophiles use 2.1 systems and I'm surprised that more front end products, eg integrated amps, pre amps, DACs etc, don't provide such an obvious improvement, one which has already been incorporated into subs themselves for a very long time.

Do said audiophiles use 2.1 without a DSP/measured room correction eq (which will also set low and high pass filters of course?). Getting a sub dialed in without dsp is a nightmare in terms of critical listening. They would be better off just using big towers for 2 channels in most cases if they need deeper base

 

[Ajax]

Do said audiophiles use 2.1 without a DSP/measured room correction eq (which will also set low and high pass filters of course?). Getting a sub dialed in without dsp is a nightmare in terms of critical listening. They would be better off just using big towers for 2 channels in most cases if they need deeper base

I doubt anyone buying such an inexpensive amp would use it for critical listening ... my point is that if you are going to add features then ensure that they can perform their intended role.

With a properly configured sub-out this could be an excellent amp for a second system using inexpensive book shelf speakers (say $500) with say a second hand sub ($200) plus a Streamer/DAC such as a wiim pro, total system cost < $1,000.

 

[mike70]

I doubt anyone buying such an inexpensive amp would use it for critical listening

It's not the price tag ... is the result / SQ .. and some of those "inexpensive amps" sounds as good as other amps with 3 zeroes in the price tag.
That's ASR mission, to show the truth.

 

[oldandintheway]

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/

I have no background in electronics, so feel free to correct me if I am wrong. I would like to question whether or not the gain adjustment mentioned early in this review is a good thing. Yes, you get a slightly better measured (and probably inaudible) SINAD result. The technical reasons for modern DAC's having 4-5 volt outputs and these small class D amplifiers having low gain are beyond me, but it is an issue if you have a system full of legacy equipment where a line level signal is expected to be 2 volts. What it means to me is that they are not really a direct substitute for many legacy amplifiers because they don't have enough gain. Comments?

 

[howard416]

Yes, you can add another box, but I'm not sure if I follow your logic?

All I'm saying is that there are so few options to make an affordable decent 2.1 system from separate components, that people are having to rely on the generosity of amp manufacturers to include the stuff to make it work.

 

[rj2wells]

+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)

I drive some in ceiling speakers with one of these, fed from a wiim. I put the input on max and the amp on min and then gradually dialed up the volume on the amp until the speakers began distorting - about half way. There it stays.

Now my wife as well as sometimes guests connect to the wiim via airplay/cast/spotify and they can put the volume to 100% and get the maximum usable volume, and I don't have to worry about some wackadoodle sending it to 11 and blowing out the speakers.

I am very glad to have the attenuator.

 

[lazerharp]

I have two of these and love them. One question. I have them hooked up to smsl DAC acting as preamp. Is it better to have the ZA3 at max and the DAC lower? Or doesn't it matter?

 

[HarmonicTHD]

I have two of these and love them. One question. I have them hooked up to smsl DAC acting as preamp. Is it better to have the ZA3 at max and the DAC lower? Or doesn't it matter?

Practically No.

Technically it optimizes the SNR when amp gain is lowest.

 

[lazerharp]

Practically No.

Technically it optimizes the SNR when amp gain is lowest.

Thanks, so theoretically it´s better to set the ZA3 lower if you don´t need the full power?

 

[HarmonicTHD]

Thanks, so theoretically it´s better to set the ZA3 lower if you don´t need the full power?

Yes

 

[Guddu]

Yes

Is setting up volume knob lower is same as having amplifier set to low again?

 

[Toni Mas]

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.

Maybe you are nostalgic about what was called these days an integrated amplifier. I personnaly don't need anymore all these (analog implemented) features, nor need anymore what was called these days a stereo preamplifier. What i need is a power stage with a volume control.

Btw i dont need either an amplifier with USB, BT, nor any kind of digital input. No interest in balanced inputs ( use short length cables)... And no need no bother with any subwoofer output, with or without adjustable xover...

Just need a few power amplifiers to hook to my sound card... More than 2 channels pocket size units warmly welcomed..

 

[musicforcities]

Unfortunately, we didn't manage to incorporate the PFFB technology into the ZA3 this time (in fact, we have recently mastered this technology).

I’ll be waiting then for the PFFB model…

There is a new fossi model every month it seems!

On the other hand, , I could really use that 12v trigger for some ceiling speakers…maybe I won’t wait.

 

[musicforcities]

I doubt anyone buying such an inexpensive amp would use it for critical listening ... my point is that if you are going to add features then ensure that they can perform their intended role.

With a properly configured sub-out this could be an excellent amp for a second system using inexpensive book shelf speakers (say $500) with say a second hand sub ($200) plus a Streamer/DAC such as a wiim pro, total system cost < $1,000.

Sure. Though couldn’t one use a DAC with variable line out ?

 

[Abstracted]

Is there a reactive load test?
I'd like to see how it responds to 2ohms.

 

[DanTheMan]

Is there a reactive load test?
I'd like to see how it responds to 2ohms.

no, unfortunately