Fosi Audio S3 Balanced HiFi Streamer

A compact, 3-in-1 balanced Hi-Fi network streamer, DAC, and preamplifier designed to serve as the digital control hub of a modern home audio or desktop system.

 

Key Features & Internal Architecture

• Flagship Audio Chipset: Built with an Amlogic A113X streaming processor, an AKM AK4493SEQ Velvet Sound DAC, and a Burr-Brown PCM1894 ADC for clean digital-to-analog and analog-to-digital processing.
• Fully Balanced Circuitry: Employs dual Texas Instruments OPA1612 op-amps in a differential configuration to feed its balanced outputs, minimizing noise and improving soundstage separation.
• Isolated Power Design: Features split digital and analog power paths, ELNA capacitors, and ultra-low-noise LDO regulators to deliver a highly accurate signal with a Total Harmonic Distortion (THD+N) of ≤ 0.00018% and an SNR of ≥ 120dB.
• High-Res Audio Formats: Supports audio streams up to 32-bit / 384kHz PCM and is capable of lossless rendering over network streaming protocols.

 

 

Connectivity Matrix

Inputs	Outputs	Wireless & Protocols
• Stereo RCA Analogue • TOSLINK Optical • HDMI eARC (with TV sync) • RJ45 10/100M Ethernet	• Balanced XLR Line Out • Unbalanced Stereo RCA • Dedicated Active Subwoofer Out • TOSLINK Optical Bridge	• Dual-Band Wi-Fi 6 & Bluetooth 5.3 (SBC/AAC) • Apple AirPlay 2 & Google Cast • TIDAL Connect & Spotify Connect • DLNA / UPnP & Roon Ready *

 

Physical Design & Ergonomics

• Chassis Build: To prevent signal blockage of its internal Wi-Fi 6 antennas, Fosi utilizes a high-quality plastic resin shell treated with a metallic space-gray spray coating. It measures 17.3 x 17.3 x 4.7 cm.
• Fascia Interface: The front panel features a prominent orange volume dial, two small control buttons, and four tiny color-changing status LEDs. Because the front panel indicators are minimalistic, configuring the device is much easier via the included Bluetooth remote control or the official mobile app

 

Performance & Sound Signature

Reviewers from audiophile forums like Audio Science Review and Head-Fi highlight that the S3 focuses heavily on clean, uncolored transparency. The AKM DAC layer yields a smooth, "velvety" signature that prevents listening fatigue over long sessions. While the top-end treble has a slightly energetic character, the midrange is highly descriptive and articulate with vocals.

The primary critique at launch is the companion app's early software ecosystem. The digital equalizer is currently limited to a basic 5-band configuration, though Fosi Audio's active global firmware roadmap includes an upgrade to a 10-band precision EQ and a streamlined UI redesign.

 

 

System Pairing Recommendations

The S3 serves as an excellent digital preamplifier to pair directly with Class-D power amplifiers—such as the Fosi Audio ZA3 or V3 Mono monoblocks—creating a highly compact, fully balanced, and audiophile-grade desktop or living room stereo stack.

 

Description:

 

All in One HiFi Streamer: The S3 combines digital transport, DAC & preamp in one chassis. The flagship AK4493SEQ DAC supports PCM up to 32bit/384kHz with THD+ N ≤0.00018% and SNR ≥120dB—delivering reference-grade sound for serious home audio systems

WiFi 6 & Bluetooth 5.3: Dual-band (2.4/5GHz) Wi-Fi and Bluetooth ensure wider coverage and faster wireless connections. Supports AirPlay 2, Spotify Connect, TIDAL Connect, Google Cast, and DLNA. Stream music from NAS or online services with ease

Balanced Circuit with Premium Components: Isolated analog/digital architecture, Japan ELNA capacitors, ultra-low-noise LDO power supply. Dual op-amp differential amplification with XLR balanced outputs, engineered for greater separation and a wider soundstage

Intelligent Control & Home Theater Ready: Easy setup with the Fosi Audio App to control playback and fine-tune the sound via EQ. With HDMI eARC and a dedicated SUB OUT, you can connect to your TV and active subwoofer to build an immersive 2.1 home theater

Reliable Streaming Amplifier with Smart Protection: 12V trigger sync, overcurrent/overvoltage safeguards, bottom heat dissipation. Compact 6.81" design—integrated amp companion with audiophile performance

 

Specifications

 

Chipset
Amlogic A113X + AKM 4493SEQ + OPA1612

Network
802.11 a/b/g/n/ac/ax dual-band Wi-Fi (2.4G and 5G) 10/100M Ethernet port

Bluetooth
Bluetooth 5.3, A2DP, AVRCP, BTLE; supports SBC and AAC codecs

Remote Control
Bluetooth connectivity with a range of over 15 meters

Power
DC 12V 1.5A

Input Sampling Rate
OPT: PCM 24bit / 192kHz
BT: PCM 24bit / 48kHz
Google Cast: PCM 24bit / 96kHz
Airplay 2: PCM 16bit / 48kHz
HDMI: PCM 24bit / 192kHz
Roon Ready: PCM 32bit / 384kHz
Wi-Fi: PCM 24bit / 192kHz

Streaming Protocols
Google Cast, AirPlay 2, DLNA, Roon Ready, Spotify Connect, Tidal Connect

APP
Fosi Audio APP Download on Google Play and the App Store

Dimensions
17.3 × 17.3 × 4.7 cm (6.81 × 6.81 × 1.85 in)

 

What‘s in the box？

• Fosi Audio S3
• Bluetooth Remote Control
• Quick Guide
• DC Power Adapter
• Optical Cable

 

FAQs

Ques: What versions of AirPlay does the S3 support?

Ans: The S3 supports AirPlay 1 and 2

Ques: What devices does the Fosi Audio App support, and where can I download it?

 

Ans: The Fosi Audio App is only available for iPhone/iPad and Android phones or tablets. You can search for "Fosi Audio" on the App Store or Google Play to download and install it.

 

Ques: The Fosi Audio App includes some feature options such as mute control and clock settings, but they don't work on the S3. What's the reason?

Ans: Some feature options in the App are reserved for future versions and are temporarily unavailable. The software is currently being continuously optimized, and we will gradually complete and unlock these features in future updates.

 

Ques: Does the S3 support Roon streaming playback?

Ans: Roon Ready certification is currently in progress and is not yet supported. Other functions work normally, and you can connect to Roon via AirPlay 2 or Google Cast.

 

Ques: Can I connect a turntable directly to the S3 streamer?

Ans: No, turntables without a built-in phono preamp must be connected to an external phono preamp first before connecting to the S3 streamer.

 

Ques: How to download S3 firmware?

Ans:

1. Enter the URL: https://support.fosiaudio.com/products/s3/

2. Click on "Manuals & Downloads", and then click on "Firmware"

3. Select the latest firmware version and click to automatically start the download

4. After the download is complete, unzip the file, and you will see two folders: "Global" and "China". You only need to keep the folder corresponding to the region you need

 

Ques: How to update firmware via computer？

Ans:

1. Open the Fosi Audio app, click on "My Device", and record the IP address of the current device (the string of numbers below the device name)

2. Turn on your computer (please ensure that the computer and the current device are connected to the same network), open your browser, enter this IP address in the web address bar, and add /settings.fcgi (as shown below)

3. Press "Enter" to enter the device's debugging interface and locate the "File" column in "Firmware Update"

4. Click "Select File" to open the file that was just unzipped, and select the folder for the corresponding region

5. Select the "image.XXX.swu" file, and then confirm. Finally, wait for the device upgrade to complet