Fosi Audio S3

The market for compact, affordable digital audio devices is currently one of the most active and competitive in all of Hi-Fi Land. From long-established and venerable brands like Cambridge to relative newcomers like WiiM, there are numerous companies ready and willing to put you in touch with the sonic delights of wireless digital audio and networking streaming without parting you from a huge amount of money or selling you a great big space-hungry box.

Fosi Audio, established in China’s manufacturing powerhouse Shenzhen back in 2017, is becoming increasingly prominent in this market, thanks to what looks very much like one of those seemingly straightforward formulas that’s nevertheless extremely tricky to pull off. The idea of developing compact and affordable digital audio equipment, offering a degree of end-user customisation, and delivering performance that belies the asking price, is hardly revolutionary - but Fosi Audio seems able to make it work far more often than it doesn’t.

This S3 is just the latest example. Here’s a compact (47 x 173 x 173mm, HxWxD) DAC / preamp / network streamer with plenty of specification highlights, wide-ranging compatibility in terms of both streaming services and connectivity, a very acceptable standard of build and finish, and an asking price of £239. It’s not witchcraft, no - but equally it’s far from usual.

On the outside, the S3 is an unassuming little box that’s available in the established Fosi Audio livery of grey with orange accents. The fascia features two rather overworked control buttons, a row of four tiny LEDs and a volume control. One of the buttons handles power on/off and input selection, the other deals with Bluetooth pairing, output selection, and can also perform a factory reset. Those LEDs, meanwhile, confirm the selected input and output, that the S3 is in Bluetooth pairing mode, or that the machine requires a firmware update. Committing the various colours and their meaning to memory is not exactly the work of an instant.

At the rear, meanwhile, there’s an Ethernet socket (for maximum network stability), an HDMI eARC input, a digital optical input, and a stereo RCA input - the digital inputs can operate at 24bit/192kHz PCM. Outputs consist of stereo RCA, balanced XLR, digital optical and a pre-out for use with a powered subwoofer. Dual-band wi-fi is on board, naturally, and there’s also Bluetooth 5.3 wireless connectivity with SBC and AAC codec compatibility.

Wi-fi (or Ethernet) allows the S3 to be compatible with the ‘Connect’ versions of Spotify and TIDAL, to work with AirPlay 2 and Google Cast, to be compatible with UPnP devices, and to be Roon Ready - used with Roon it’s able to deal with resolutions of up to 32bit/384kHz. By the time this review is published, there’s a good chance the Fosi Audio will be compatible with Qobuz Connect too - if it isn’t, it will be very soon.

Any and all incoming digital audio information is dealt with by a chipset that includes the AKM 4493SEQ DAC and Texas Instruments OPA1612 op-amps laid out in a balanced configuration. Or, at least, it does if you’re using the S3 as a DAC and/or a pre-amp - it’s possible to set it up purely as a network streamer, of course, by using its digital optical output to connect to an external DAC or preamp.  

sound quality

Connected to a system via its digital optical output and used simply as a network streamer, the Fosi Audio S3 has plenty to recommend it. Compared to the (much more expensive) Arcam streamer I use as a reference it’s short of the last shred of fine detail and is relatively lacking in outright drive and dynamism, it’s true - but in the context of the asking price it’s a balanced, informative listen, one with a decent grasp of organisation. Even when streaming enormously information-packed 24bit/192kHz content it remains composed and insightful.

Let it take care of digital-to-analogue conversion by connecting it to a power amplifier via its balanced XLR outputs and, if anything, it’s even more likeable and accomplished. It controls its fairly large and nicely defined soundstage well, and makes the layout of even quite complex and/or involved recordings explicit and easy to follow. It’s quite adept at giving the spaces between performers on the stage due prominence, too. Its tonal balance is fairly neutral (although there’s a fairly spirited rendition of the higher frequencies that won’t sit all that well with similarly treble-happy amplification and/or loudspeakers), and its frequency response is smoothly even-handed from the deep and textured low end to that lively treble.

It shapes bass sounds quite carefully, and is attentive to the attack and decay of individual occurrences at the bottom end, so there’s decent rhythmic expression available and a good sensation of momentum in those recordings that require it. It’s in the midrange, though, that the S3 does its most appealing work - it can extract quite a lot of fine detail from a voice (whether speaking or singing) and explain it in terms of character and attitude as well as tone and technique. It communicates very freely through the middle of the frequency range, and is all the more engaging to listen to as a result.

There’s appreciable dynamic headroom available, so any upticks in volume or intensity in a recording are made obvious rather than being alluded to. The Fosi Audio does good work with the more nuanced (but no less important) dynamics of harmonic variation, too. And despite its tendency to attack the top of the frequency range with unnecessary fervour, the S3 manages to hold its overall presentation together in a nicely unified manner - the vexed question of ‘timing’ is never really an issue.         

living with

Obviously the Fosi Audio S3 is not a large box - it’s less than half the width of a standard hi-fi shelf, and so will fit pretty much anywhere you need it to. And visually it’s not about to draw attention to itself when it’s there.

In terms of operation, you have a few options. There’s the rather counter-intuitive selection of buttons and tell-tale LEDs on the fascia I’ve already discussed - but the S3 also ships with a small and unremarkable remote control handset that is a fair bit more logical. It still only has a button to scroll through inputs rather than having one button per input, it’s true, but I guess you can’t have everything… 

There’s also a control app that’s free for iOS and Android. It’s hardly the last word in visual excitement, and it could be more straightforward to navigate - but as well as giving access to each source individually (both physical and wireless) and allowing you to specify the output you want to use, it also allows volume control, gives access to a five-band EQ, informs you of available firmware updates, and has all the network set-up access you need too. It’s generally stable and fairly logical after a period of acclimatisation.

conclusion

This is not Fosi Audio’s first rodeo - but the S3 could be the product that brings it to wider attention. There are more accomplished streamer / DAC / preamps around, sure, and they almost all are better where ergonomics are concerned - but if you’re interested in a value-for-money proposition down towards the entry-level of the world of network audio streaming, you ignore this device at your peril. 

listening notes

‍Bill Fay I Hear You Calling
The intimate, immediate nature of the voice in particular and the midrange in general is the highlight here, and the S3 is more than capable of teasing out the nuance and emotion in the delivery. It’s no slouch when it comes to controlling the tempo, either.

Joni Mitchell You Turn Me On, I’m a Radio
Warmly organic in sound and attitude, performed by an ensemble of absolute virtuosos and with a rhythm that just rolls along without any apparent effort, this is a recording that allows the Fosi Audio to showcase its naturalistic and direct way with timing and integration of the frequency range.  

‍Natural Magic Another Club Another Banger
The varied nature of the tonality of this motorik slice of full-on Kosmiche freak-out (somehow recorded in 2026, even though it’s quite obviously attempting to sound like it’s 1975) is expressed with real confidence by the S3.

Fancy some uncomplicated and uncomplicatedly enjoyable network streaming, perhaps with some DAC and pre-amp functionality thrown in, without spending an arm and a leg and without occupying too much valuable hi-fi equipment rack shelf space? Fosi Audio has you covered with the S3…

Persevering with the ‘small and beautifully formed’ theme, the Cambridge MXW70 is a compact, high-achieving power amplifier that’s absolutely ideal as the business end of the S3’s streaming, DAC and pre-amplification heroics.