Fosi Audio ZA3 Class D HiFi Stereo Amplifier Review
Fosi Audio made a splash with their extremely affordable products. The ZA3 especially caught my attention, as I adore both my headphones and my stereo.The ZA3 is currently the top integrated amp from Fosi, bettered only by the freshest V3 Mono, which is a single-channel power amplifier. Both use one of the best class-D chips from Texas Instruments, although in different implementations. Back to the ZA3, why it’s so popular? It’s a set of features and final sound quality. A set of features focused on sound quality to be exact. More power than you’ll need. No problems with driving low impedance. Great specs. Looks nice. Sub out.
Packaging
Everything comes in a blue box. That’s it. It’s a solid box, with hard foam inserts. A proven and budget-friendly solution. Inside, you’ll find the amplifier, power supply, and mains cable. It is as barebones as can be to keep the price low.
The attached manual explains how to connect everything and has a small paragraph about swapping opamps. It is very short and lacks info about recommended types. It shows a picture of a stock NE5532 and a picture of Sparkos SS3602 and explains how to identify pin 1 of an opamp. Nice tip, if you don’t know.
Design and Build Quality
The chassis is all aluminum. The main part is a piece of an extruded sleeve, capped by front and rear panels. The color scheme is dark grey and orange accents: the volume knob and ventilation nets. There is also a variant with a dark grey knob, but I heard it doesn’t sell as well. Guess we all need a bit of color pop in our lives. In the back you’ll find small 2-way binding posts, accepting banana plugs and bare wire. They are really tiny, so I recommend using banana plugs for convenience. All in all the build quality is really good for the price and my biggest complaint for inconvenient speaker connectors is due to size constraints.
Inside, we’ll find a lot of high-quality parts from the biggest brands like Wima, Nippon Chemicon, or Elna. There is absolutely nothing to complain about. Stock opamps are the ol’ reliable NE5532 from Texas Instruments. But that is up to you… For the design portion, I really wish the front stereo/mono switch was moved to the back and replaced by a gain switch. When using the ZA3 in a close field, the gain was sometimes too much. With no remote, it is a primary setting for it.
But then we have to take a look at the whole lineup of Fosi Audio products. And there is a problem. Why in the hell does every single one of them look different and have a different size..? Reviewed Fosi Audio ZA3 looks different than DAC/pre ZD3 which looks different than V3 monos. There is also an LC30 speaker selector that is a useful thing for people like me swapping stuff all the time, which looks different than the rest and has a different form factor than all of the rest. I really wish they had a more unified design, especially devices that are supposed to go together.
Tech
The heart of the Fosi Audio ZA3 is TPA3255, a class D amplifier made by Texas Instruments. For some time it’s been regarded as one of the best amplifiers in its category. It provides a ton of clean power, giving the Fosi Audio ZA3 up to 155W @ 4Ohm per channel with the 48V power supply. With a 32V supply, it goes down to 95W @ 4Ohm per channel. The amp can work in mono mode delivering 235W @ 4Ohm and 110W @ 4Ohm respectively. Impressive numbers for such a small unit, but remember that the power supply is separate and is actually bigger than the amp itself. My version is the 48V one.
The TPA3255 here is used without Post Filter FeedBack (PFFB) technology, which is used in the V3 Mono. This technology offers even lower distortion and lower output impedance, but even without it, we are looking at impressive specs. The ZA3 cites THD < 0,006%, but no information about how it was measured. Inside the amp, you’ll find a rather complex preamplifier with XLR/RCA inputs, sub out and a line stage. Each of those has swappable opamps in DIP8 sockets allowing you to tune the sound to your liking. It is encouraged by Fosi, so go ahead and have fun. I’ll be reviewing the stock configuration with NE5532s, but had some fun with discrete opamps and can tell you it’s fun.
The amplifier has one XLR and one RCA input. The internals aren’t fully balanced and the XLR inputs are handled by a dedicated opamp. Sub out is a very pleasant addition, I have supplemented my KEF LS50 with Audiovector Mi Sub Signature to great effect. Reviewed Fosi AudioZA3 is designed as a barebones amplifier with two inputs. The only option for remote control is the trigger input in the back. It has its ups and downs. On one hand, all of your money goes directly towards performance. On the other, you need to get your ass off the couch to change the volume or source. Which can be tough after a 3rdhot toddy. I really wish Fosi would release a full-sized integrated amp with multiple inputs, phono, DAC, and amp sections like this one. That would be a painful kick in the nuts for fat cats of audio who only annually change the price of their products.
The sound of the reviewed Fosi Audio ZA3
In short, the reviewed amp keeps the sound neutral. It follows the “wire with gain” route. What stands out to me is the amount of detail and control it holds over speakers, even those hard to drive. You might say that the KEF LS50 Meta is not a suitable desktop speaker, but… It was a fantastic-sounding setup. They take a ton of space, yes. They have low sensitivity, yes. Yet they worked beautifully with the ZA3. A really good coaxial driver in close field does wonders both in games and movies.
It replaced the SMSL AO200 MKII in that role. I did some opamp swapping and can confirm that it is absolutely worth it. Sparkos SS3602 and Muzg Audio dual were clear standouts. I would say they helped tested Fosi ZA3 reach the next level of performance. For the review, I’ll stick to stock opamps, to give you the most out of a box impressions. With that much power comes a lot of control.
ZA3 handled a wide variety of speakers with zero issues. Bookshelf, floor standers. Even some ceiling speakers on one occasion. It is noteworthy how well the Fosi Audio ZA3 works with much more expensive equipment. In my experience, it absolutely handles speakers a couple of times more expensive than it is. Thanks to its resolution and cleanliness it can really deliver with really good accompanying equipment.
Bass
Reviewed Fosi Audio ZA3 is clean and powerful. It delivers what is recorded, and adds nothing. I loved how easily it handled every speaker in that regard. Multi-driver Pylon Pearl 27, low impedance and sensitivity KEF LS50 Meta made no difference for this little amp. It has complete control over the drivers. The lows are tight and have really good detail. Listening to Bob Marley’s Buffalo Soldier is a great example of how it handles bass notes: great textures and great extension. Extra power really helps to extract as many low frequencies as possible, even from small speakers.
On the other hand, Pylon Audio Pearl 27 has a lot of bass with a bottom-heavy tuning. I was curious how it will handle contemporary pop with a big, synth bass. So I listened to The Weeknd’s Save Your Tears and I’m happy to report that ZA3 hasn’t allowed the bass to be unnecessarily boomy or loose. It had ample weight and punch, characteristics I look for in this type of music. The dynamics even in larger rooms were unparalleled by the competition. The amount is spot on and it doesn’t bleed on the midrange. Speaking of which…
Midrange
It excels at dynamics and detail. Guitars in Southbound Again by Dire Straits are snappy and engaging. They draw you in instantly. The attack is fast and precise. Mark Knopfler’s vocals are presented a little behind the guitar. This also connects with how the sound staging is built, later on that. If you prefer warmness and richness, then ZA3 is not for you. Here you have a direct, uncoloured sound. You’ll get what you give, both in terms of source material and connected equipment.
Another song I played was No Light No Light by Florence + the Machine Unplugged. It further highlighted the technical and dynamic prowess of this surprising amp. It effortlessly goes from quiet to loud parts, with no loss of fidelity or tonality. The accompanying piano was completely separated and wasn’t influencing the vocals – something that often happens at this price range.
Treble
Is crisp and detailed. Long gone are times when class D had terrible top range. Even without PFFB, the ZA3 delivers excellent results. The cymbals in Bishop School by Yusef Lateef flow freely, nicely and smoothly. I like how clear-cut and separated they are. The precision and control of Fosi ZA3 come back again.
Then I tried something really tough: Bamboche by Jean-Louis Beaumadier. It shows that while in its price range, ZA3 performs really well and often above expectations, it shows its limitation in treble first. While it nimbly tackled the task at hand, it didn’t have the class and detail presented by a more expensive class AB amp. On the other hand, in this price range, it’s mostly class D amps anyway.
Soundstaging
The Fosi ZA3 builds the space in between the speakers, with a surprising reach to both sides. It does struggle a bit with depth. It shows in Take Five from the album Jazz At The Pawnshop by Arne Domnerus.
Precision is on point, with clear sound sources. As mentioned before, it performs really well with width, but due to shallow presentation, it builds a soundstage which is far (between the speakers) and relatively flat as it doesn’t come too close to the listener. On the other hand, its direct competitor does the opposite. It’s narrow but deeper, so pick your poison.
Fosi Audio ZA3 Review – Summary
Well, what Fosi ZA3 actually is? It’s an incredibly capable, yet extremely barebones integrated amplifier that has an extremely affordable price. If you’re looking for an amp that won’t add anything and drive everything, you’re golden. This is exactly what it is.
“Wire with gain” sound signature, meaning you get what you give. It handles basically any reasonable speaker in any reasonable room. Even if it isn’t on the performance level of accompanying equipment, it still sounds just good, not cheap or bad. Fantastic way of getting into stereo, or a temporary amp for the future.
For many: first and last amp they’ll buy. If that sounds up your alley, then there isn’t much else on the market that matches the value of this little amp. Kudos to Fosi Audio for bringing this gem. It’s an instant classic.
Highly Recommended!
