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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
I believe with a review like that, the numbers are simply assigned arbitrarily.

If the amp works well in your use case, it's a good one for you, and if not, then it isn't.
 
I might want to use this amp to run a secondary set of monitors in my home studio. I want to control the power to my main monitors and this amp with a single power switch.

Can you (safely) control the power away from the device? And will the speakers be protected from loud bursts?

And how about the V3? I'm still undecided between both.
 
mav said:
I might want to use this amp to run a secondary set of monitors in my home studio. I want to control the power to my main monitors and this amp with a single power switch.

Can you (safely) control the power away from the device? And will the speakers be protected from loud bursts?

And how about the V3? I'm still undecided between both.
Click to expand...
Hi MAV that will be possible, when switch also the 12Volt Trigger on. ;)
 
Mikig said:
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.
Click to expand...
I am thinking same. $ for value should be it's own metric perhaps. What would compete with it for that $? I'm looking to do a desktop/office system, and that's perfect and $ fair. I just ordered one.
 
Last edited:
Does the subwoofer out on this unit operate in digital domain? I am wondering if the signal is going through an additional AD and then DA conversion. If that is the case, it may be preferable to simply split the signal out of a DAC and feed it to a subwoofer and adjust the low pass filter crossover frequency there.
 
I have a few questions: Does changing the XLR op-amp in the ZA3 amount to any improvement or change in sound? Also, how can leaving the op-amps empty result in a sound improvement? Is really true? Is it okay to run the op-amps empty?
 
jbucla2005 said:
I have a few questions: Does changing the XLR op-amp in the ZA3 amount to any improvement or change in sound? Also, how can leaving the op-amps empty result in a sound improvement? Is really true? Is it okay to run the op-amps empty?
Click to expand...
There are people running the ZA3 with unused op-amps removed without any issue. Whether changes are audible is up for debate. I don’t know if anyone has taken actual measurements of with op-amps versus without.

-Ed
 
I am using a Fosi ZA3 to power Elac Debut 2.0 B6.2's with Elac Sub1010. I use the XLR inputs from a SMSL DL200 dac. I use the subwoofer output on the back of the amp. I changed all the op-amps to Sparkos SS3602. The sound is great and there is tons of power. I can't even turn it up to 25% before it gets too loud. I'm using these near field. I tried the ZA3 as dual mono but it didn't work as well. I had to use the volume on my dac, while keeping the amps turned up, and it didn't sound as good.
 
Without reading through 27 pages here, plus the rather fuzzy Fosi site, what's the real full bandwidth rated power on this amp and not the worthless 1khz test tone rating? You know....20hz to 20khz maybe.
 
amirm said:
Manufacturer Specifications:


View attachment 348848
View attachment 348849
Click to expand...
amirm said:
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.

------------
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/
Click to expand...
This report convinced me to buy one to use as a subwoofer amp. I purchased without a power supply for 109.00 on the Ebay Fosi store and then bought this 48 volt amp that I am sure is better than the Fosi one.... ( At least it's in a metal housing. ) https://www.amazon.com/dp/B087G5RLWJ?psc=1&ref=ppx_yo2ov_dt_b_product_details
 
jbucla2005 said:
I have a few questions: Does changing the XLR op-amp in the ZA3 amount to any improvement or change in sound? Also, how can leaving the op-amps empty result in a sound improvement? Is really true? Is it okay to run the op-amps empty?
Click to expand...
I’m using mine mono xlr with the op amps removed in the unused channels, the stock op amp in the differential position and a Sparkos op amp in the driver position. I can’t comment on whether it sounds better with the other op amps removed, but it definitely doesn’t sound worse. I’ve been using 4 of them configured this way for around 3 months, driving the woofers and tweeters on a pair of diy 3-way horns. They were an improvement over the class A and class AB amps they replaced.
 
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