Fosi Audio ZA3 Amplifier Review

[dixter]

you guys are funny to read... in more ways than one...

 

[Toslink]

You really can't ask for more than this in a $149 amp! Entry level amps and DACs now at astonishingly low prices.

Agreed. It'd easily be a first choice for me if I were just getting started as a young audio enthusiast seeking to assemble a music system. It's pretty astonishing what one can buy in the amplifier and DAC category these days for very little. The price vs performance ratio is astronomical.

 

[Urib]

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:
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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:
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Continuing with XLR input testing, noise performance is excellent especially for the class:
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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:
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This means depending on your speaker impedance, high frequencies may be exaggerated a bit.

I measured subwoofer out and it seems good enough:
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Note that I was driving it from XLR input and it still routed that to the RCA sub out.

Crosstalk is very good:
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Using balanced input nicely eliminated low frequency spikes in low frequencies:
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Distortion does increase at higher frequencies though so 19+20 kHz intermodulation doesn't impress:
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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:
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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:
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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/

Thanks, for another great review. I personally don't consider buying any thing, before reading ASR review. It is the most important audio website out there and we are lucky we have Amir for his help improving the industry. Thanks again!

 

[Palladium]

Somewhere along the way I read the op amps included may be clone NE5532's and somebody replaced them with real 5532's and it was better. I just bought some, hopefully, genuine Texas Instruments NE5532's and Burr Brown OPA2604's off eBay and I'm going to find out. I've got about $40 into this experiment.

I am very sure this was a myth busted by Fosi themselves posting their NE5532 purchase orders in the V3 thread.

Back to the ZA3, I agree its of poor value relative their own V3.

 

[JSmith]

Not a bad little amp... balanced input is a plus, but unsure if worth the premium over the V3. Not so keen on the load dependency noted, but then again this is expected in these TPA3255 amps. The bass roll-off is unwelcome, but is only .5dB I suppose. All in all, nice to see the results on this anyway @amirm, as there is certainly a strong market.


JSmith

 

[375HP2482]

There is a picture of the internals here:

https://audiosciencereview.com/foru...ode-balanced-amplifier-za3.48552/post-1762896

It does have relays… And Fosi confirmed the “mono” mode is actually PBTL (the TI term for this parallel bridge-tied load mode):

https://audiosciencereview.com/foru...ode-balanced-amplifier-za3.48552/post-1789801

Yes, it needs a DPDT relay to switch, for example, the C OUT pin between the C output filter and the A OUT, and the D OUT between the D output filter and the B OUT. Additionally the M2 pin needs to be switched from GND to VDD, probably by the MONO switch that activates the relay. You end up using all 4 output stages for just two output branches, doubling the current capacity for the single MONO channel and spreading the chip heat over the entire heatsink pad. Seeing as you are voltage-limited by the supply, the main benefit of MONO operation is with 2-ohm loads, which should result in an even more overdamped HF frequency response and increased choke nonlinearity since you're still only using one pair of output filters in PBTL.

Outboard power supplies can have their benefits. With relatively modest ones like these they are usually small enough to be hidden at a distance from the unit. When electronics fail, especially more economic ones, the power supply is often what dies, and it's easier to just replace the power brick than to chuck the whole unit. Laptops, monitors and set-top boxes moved their supplies outside long before internal space became so critical.

 

[Talisman]

Somewhere along the way I read the op amps included may be clone NE5532's and somebody replaced them with real 5532's and it was better. I just bought some, hopefully, genuine Texas Instruments NE5532's and Burr Brown OPA2604's off eBay and I'm going to find out. I've got about $40 into this experiment.

Now ENOUGH with this false information, it had already happened with the V3 and the company intervened by showing the original purchase invoices from Texas Instruments (and was in no way required to do so), let's not spread these false rumors, no matter how we know about it and from what the company has demonstrated all the components are original and genuine, claiming otherwise is akin to slander.

 

[IAtaman]

Somewhere along the way I read the op amps included may be clone NE5532's and somebody replaced them with real 5532's and it was better. I just bought some, hopefully, genuine Texas Instruments NE5532's and Burr Brown OPA2604's off eBay and I'm going to find out. I've got about $40 into this experiment.

Can you share where you read that?

 

[DanTheMan]

Lets see if it comes close to the 3e audio 260-2-29A amplifier, as this seems to be the "state of the art" for TPA3255 based amplifiers.

Regarding this ZA3:
a) it measures worse than the V3
b) it costs more than the V3
c) it has a poor XLR implementation
d) it has a poor mono implementation
e) it seems to have better heat dissipation (and cabinet)

Simply adding a gold anodised knob and a few more switches does not constitute audio engineering; it is merely a lazy marketing tactic to boost sales.

Innovation is defined as something new that brings satisfaction and value to the customer. Therefore, an audio company should focus on providing genuine value to the customer.

Consumers do not typically perceive gadget features, lower specifications, and higher prices as innovation. Good engineering is what truly constitutes innovation.

Fosi Audio had to balance innovation with marketing for both the Chinese and global markets.

Excuse my ignorance, but what makes this XLR implementation a poor one? I’m looking into having this run my speakers make for my keyboard.

 

[DanielT]

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.

In practical, audible terms, especially if you are a bit older and have lost the ability to hear higher frequencies that you heard in your youth, it is a question of whether you can hear the tiny little load dependency? BUT I just find it strange, or bad, with amps that don't exhibit pancake flat FR. Would the price increase that much if a sensible PFFB were added to this amp? Would its power decrease much? Or is it due to something else?

 

[DanielT]

Then we had likes of Hypex and brought the filter into the amplifier feedback loop, thereby negating its load dependency. This has to be carefully done as to avoid oscillations. The IC uses here for amplification has that capability so it is a matter of implementation and any extra cost.

An additional cost, I understand that but is this additional cost that high?

 

[Hipocrates]

I've been observing this place.
Amir make a extremely well made review of a budget product that is well engineered, usually with desktop/convenience application in mind.
Then a bunch a grow up man rants for hours about how the design does not fit their personal application/Wishlist of features/prices or a dB here and there, with a lot of passion I must say.
Is very strange.

 

[amirm]

An additional cost, I understand that but is this additional cost that high?

I don't actually know the cost differential.

 

[iLoveCats]

Can you share where you read that?

No idea, not here, few people here care about op amp and tube rolling. Either YouTube comments or another forum I found from Google results. I did not see the purchase order posted here from Fosi. We have several threads here with ZA3 and V3 information mixed together. Had I seen that I would have saved $20 on other NE5532's and just got the Burr Browns. I will edit my post that the 5532's have been proven legit.

 

[iLoveCats]

Now ENOUGH with this false information, it had already happened with the V3 and the company intervened by showing the original purchase invoices from Texas Instruments (and was in no way required to do so), let's not spread these false rumors, no matter how we know about it and from what the company has demonstrated all the components are original and genuine, claiming otherwise is akin to slander.

I will edit my post. I feel like I saw everything on this forum related to the ZA3 but apparently not this purchase order. I'm still going to try what I bought but I guess I could have saved $20.

 

[jmillar]

+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 LIKE the volume control. In future it might be a good idea to provide a volume "bypass" switch to fully satisfy some users.

 

[Talisman]

No idea, not here, few people here care about op amp and tube rolling. Either YouTube comments or another forum I found from Google results. I did not see the purchase order posted here from Fosi. We have several threads here with ZA3 and V3 information mixed together. Had I seen that I would have saved $20 on other NE5532's and just got the Burr Browns. I will edit my post that the 5532's have been proven legit.

At the end of the V3 review Amir inserted an Edit about it to close the question, you can check it yourself

https://www.audiosciencereview.com/forum/index.php?threads/fosi-audio-v3-amplifier-review.45757/

 

[Sir Sanders Zingmore]

Can anyone answer the following question; what is the detectable threshold level of SINAD for amplifiers?

I'd be far more concerned about the load-dependent frequency response

 

[jaakkopetteri]

+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)

Hoping to see a power amp version with PFFB and a gain switch, as my cat likes volume knobs and screwing up my MSO setup

 

[DavidK442]

Have purchased three of these little class D amps in the last two years, even though I only have an on-going use for one. Thought the ZA3 might be number four, but I will wait. Though I likely can’t hear the difference would love to see something in this price range with specs closer to the Topping PA7+. With the rate of evolution, driven primarily by ASR’s relentless testing, maybe one day.