Great little amp.My stack is a Wiim amp pro (for streaming and eq), Fosi ZD3 preamp, and Fosi ZA3 with the 48v power supply running in stereo mode. Mostly run from an apple tv sending hdmi to the tv then optical from there. The whole setup was easily under $500.I chose this setup in case I needed more power, I can simply add another amp and run mono, but it's definitely not needed. Runs a pair of Q Accoustic 5020s easily to unlistenable levels in a small/med size room (450sq/ft).I have the whole stack switched with a smart plug and haven't had any issues with powering off or on (unlike my last set of powered Swans speakers which blew up on power up).I was occasionally getting a little pop on power up and also a computerized "bzzzrt" very occasionally during listening. I just googled and found there was a firmware update for the Preamp (no issue with the amp). Just contact Fosi support and they give you the url for the updated firmware. Easy to install with a windows laptop and usb cord. Haven't had either issue since. Really nice to see firmware updates so quickly! So used to products this cheap being treated as "disposable" and not getting real support.It's only been a month, but very happy with the performance and the support. I think it really helps that there seems to be a lot of love in the stereo community for this product. I hope it continues to get firmware updates in the future.The set looks really clean and very minimal. Used to do the whole rack or shelf system of components, but I'm over it. I tried to hide everything, but unfortunately, the IR signal wouldn't hit where I had it. Maybe I'll add an IR repeater in the future.There is one downer on this product. It has a sub out which is great. But when you connect a subwoofer, it still sends full signal to the speaker outs. At high volumes you can hear the small bookshelf speakers trying to put out bass that's not really needed with a sub. Makes me wonder if the sub out is also full signal. If so that seems like an oversight. Not sure how the sub filter would work but it would be great if it's something that can be added with an update.Originally only had the Fosi stack, but this and some weird room acoustics convinced me get the Wiim amp pro to use as an EQ. I just put a -3db shelf filter on for everything below 80 hz. My SVS SB1000 sub has tons of headroom so I just upped the gain a bit. I debated on returning the ZD3 preamp and just running the Wiim to the ZA3, but I am really liking the look and sound as it is now so I'll prob leave it as is.

I ordered a Fosi ZA3 from Amazon this past Wednesday and it arrived yesterday morning. Upon unboxing the nicely packed amp and 48V-5A power supply, both pieces were ice cold, so I had to allow for everything to warm up to room temperature before powering anything on.I connected the ZA3 amp to my Audio Research LS7 tube line stage, and played back tracks through my Raspberry Pi 4 running Volumio 3 connected to an SMSL SU-9 V. 2 DAC. Over a period of 2-3 hours, I could hear the sound signature changing from a bright, etched sound with narrow image and small soundstage to a warmer, full-bodied sound whose soundstage expanded beyond the outer boundaries of my modified Klipsch Forte 2 speakers. The image projected slightly in front of the speakers to behind them and grew in height. I could feel the bass lines coming through the floor and felt the impact of some deep notes through the air. With the Klipsch speaker efficiency rated at 98dB, I found myself dialing the volume down a couple steps as the amp burned in.A friend recommended leaving the ZA3 powered on, so I left it on all night with the volume turned all the way down. When I spun some vinyl the next day, I was really impressed with the scale of the soundstage compared to what I heard the previous day. The music has a really solid foundation in terms of imaging and separation. The musicians all have their place in the soundstage, and the tonality is very rich. This amp digs more deeply in the lower bass compared to my Pass DIY Sony VFET Class A amp and the McIntosh MC-240. It’s very dynamic with nice, sustained notes. It’s crazy how great this amp sounds for the $130 I spent on it.In the last photo, the Fosi ZA3 is sitting on top of a Pass DIY Sony VFET push-pull single-ended Class A amp I built several years ago. Next to that is a McIntosh MC-240 tube amp I had rebuilt with new power supply and coupling caps. Over the next several days while I have time off from work, I will compare these amps using my analog set-up, and the above-mentioned digital source:- Technics SL-1200GR- Audio Technica AT33/PTG II LOMC cartridge- Audio Research PH5 tube phono stage - single-ended connectionI split my time between two homes for my work. At my other home--an apartment--I plan to take this amp and try it out in the system there:- Bill Neumann (Fix My Dual) rebuilt Dual 1229 idler wheel-drive turntable- Shure V15 Type III MM cartridge- Schiit Mani 2 phono stage preamp - single-ended connection- Raspberry Pi4 running Volumio 3 USB-based streaming source- Denafrips Pontus 2 R2R DAC - balanced connection- Schiit Freya+ Tube/SS line stage with OS GE 6SN7's with side-getters (gain stage) and Tung Sol 6SN7's (driver stage) - balanced connection- Pass DIY Aleph J Single-Ended Class A power amp - balanced connection- KEF LS50 speakersIt's with this system that I am most interested in trying the Fosi ZA3 with balanced connections driving the less efficient KEF LS50 speakers. The Copper accents on the Fosi ought to coordinate well with the Copper-colored drivers on my KEF's.I've ordered some op amps from Fosi Audio to try out as well:- Texas Instruments OPA2134- Nisshinbo MUSES02

I love the size of the units, I'm running 2 za3 in dual mono, with the fosi zd3.And the footprint is very small😊I've run the set up through at least 3 sets of my available speakers, with and without my subs.The sound is very good!I'm not sure i really need to mess around with opamp rolling...I'm using it in balanced, so I guess at the least I could remove the unused left opamps...But for now I'm listening to everything I have, in vinyl, cd, and streaming! It sounds awesome!Thank you Fosi for making affordable hi-fi!I have at least 5 other units of your products, and all have been excellent!

This small amplifier is well designed and good value for the money with connectivity for many options.It is ideal for anyone needing a small desktop or bedroom amp especially.For music sound quality you would be better served by buying the entry level receiver from Yamaha.These small amps just can’t compete with the larger integrated or power amps for music listening .That said,I am keeping this as it works well and the Fosi people did a good job designing and implementing this. I am looking forward to future products they introduceThe ZA3 has a clear sound with defined left and right separation, the trade off to this benefit is a shallow depth soundstage and lean BassBass is there, just not a lot of authority.The ZA3 may work best in conjunction with a preamp as at low volumes the potentiometer is touchy

I used this amplifier to drive the JBL 530 which is a 6 ohm nominal load and 86 db/w sensitivity speakers and it drives them at all levels easily with no noise whatsoever, the character of this speaker/amp pairing is a bit laid back in mid range, fast and tight thumping bass, slightly rolled off in the treble,I’ve found the best dynamics with the potentiometer somewhere between 11:00-01:00 o’clock and the windows volume betwen 60-70%(Vrms of 1.95V DAC line-level output), this gives me about 70 db average listening level with 30+ db of dynamics headroom.I’m looking to try other op-amps in this amplifier and see how it affects it tonally, overall I’m plenty happy for such a good price and lower size profile that this amplifier provides, well done Fosi!

48v 5A adaptörü takıp kendi dahili dac.ı rca ile denedim evet ilgi çekiciydi fakat standart bi d -classtı. Daha sonra 3 adet muses02 opamp sipariş verdim ve elime ulaşıncaya kadar amfinin yanmasını bekledim. Nihayet geldi opampları değiştirdim ve sub opampı devre dışı bıraktım(kullanmadığım için) vee Xlr (cardas golden cross) ları bağlayınca vaaay müthiş ses!!Birçok pahalı amfiyi sınıfta bırakır çok net!! Opamp yükseltmesi yapıp güzel bir Xlr ile kullanınız şaşırcaksınız....

El Fosi ZA3 es un amplificador bastante económico con mucha potencia. No altera el sonido y reproduce exactamente la calidad de la fuente/DAC. No se aprecia distorsión y el balance es bueno. Muy importante la capacidad de usarlo como Monoblock si se implementan dos unidades.Pros:- Rendimiento/Precio imbatible.- Potencia de sobras y capacidad de hacer monoblock con 2 unidades.- Conexiones traseras, RCA - XLR - SUB Out.- Facilidad de uso y conexión.- Unidad con un tamaño perfecto, no aparenta tener la potencia que tiene por el tamaño.Contras:- Podría ser más sencillo de encender y apagar.- Petaca de alimentación de 48V bastante voluminosa (Entendible).

Needed something compact to run my bookshelf speakers in a limited space area.Bought a second ZA3 to match up with my other ZA3, both set in MONO modes.These sound great and have plenty of power running my high efficiency speakers.Great performance and great price!

*4 Month UpdateAfter using this amp for 4+ months and applying room correction to my system (via WiiM) I am actually happier than I was when I first tested and have therefore increased the star rating. I'm not sure if this is burn in or I've just done a better job with EQ now, but the amp paired with my WiiM Pro Plus and very basic (15 year-old) Sony Bookshelf speakers actually sound quite good. I'm yet to test with a better set of speakers, but I'm sure results will only be more impressive. I probably need to test with more sources, but this is a solid little amp! 👍*Initial review below.This is a nicely made and very powerful little amp for a very reasonable price.My system:- Fosi Za3 (48v PS)- WiiM Pro Plus connected via RCA- Sony mini-Hi-Fi bookshelf speakersIs it as good as they say?In terms of sound, on my system I need EQ (on WiiM) to bring the mid's forward and lift the bass a little. Without adjusting EQ the vocals are not clear enough and the bass is a little lean. After EQ the experience was much better for me, not amazing, but much better.Fosi appear to endorse Op Amp rolling, which I think may be a hint that the factory op amps are not the best available but allow Fosi to hit a price point. I will probably experiment in future but the more highly regarded op amps are expensive comparatively.If you are expecting an audiophile grade experience out of the box, you may find yourself a little disappointed. However, if you need a small but powerful package and are able to tweak EQ and or upgrade op amps, you may well get results you're happy with.All in all, a fun piece of kit which has brought my old system to life and I do like it. If you have spent a lot on speakers and want an audiophile experience please go to a store, listen and buy that way.