Fosi S3 Streamer Preamp- Vintage Audio Review Episode #223

Fosi S3 Streamer Preamp- Vintage Audio Review Episode #223

Fosi S3 Streamer Review

Introduction to the Fosi S3 Streamer

  • The video introduces the Fosi S3 streamer, which also functions as a preamplifier. It is priced at approximately $260 on Amazon as of mid-May 2026.
  • The reviewer clarifies that they received the unit for free but are not compensated beyond keeping it for review purposes.

Features and Specifications

  • The Fosi S3 includes various inputs: optical input/output, trigger output, line input, and Bluetooth compatibility. It can be controlled via a dedicated app.
  • Notably, it lacks support for Amazon HD music streaming but does support Spotify through its app. Users can select their streaming device within the Spotify interface.

Included Accessories

  • The package comes with a 12-V wall wart (not USB), a standard remote control requiring two AAA batteries (not included), an optical Toslink cable, and an owner's manual. Overall build quality is described as satisfactory.

Performance Testing Overview

  • Initial tests involve measuring signal-to-noise ratio (SNR) and total harmonic distortion (THD) using a standard 1-kHz signal at maximum gain settings; results show excellent performance metrics with low distortion levels around 0.0009%.
  • Further testing reveals THD versus frequency data indicating minimal distortion across various input levels when using RCA connections; however, caution is advised against running at high dBV levels due to potential distortion increases.

Audio Quality Insights

  • Frequency response tests indicate good channel balance and flatness across normal audio ranges with minor deviations noted at extreme frequencies (20 Hz and 20 kHz). Overall performance remains strong in terms of clarity and fidelity during playback from NAS drives or UPnP sources.
  • Crosstalk measurements demonstrate superior performance compared to other devices tested, exceeding 100 dB crosstalk reduction capabilities under specific conditions. This suggests effective isolation between channels during operation.

User Experience Challenges

  • Issues arise when using the Fosi S3 with UPnP/NAS drives; users report limitations such as only being able to view up to 31 folders or songs at once, making navigation cumbersome compared to competitors like Wiim Mini which offers better file visibility and search functionality.
  • Additional concerns include lack of volume indication on the unit itself—only visible through the app—and small LED indicators that may be difficult to see in low light conditions while adjusting volume increments of about 2.5 dB per button press on the remote control.

Conclusion on Usability

  • While sound quality is praised when playing test tracks directly accessible from NAS drives, usability issues detract from overall experience; firmware updates are suggested for improvements in user interface functionality and additional streaming service support like Amazon Music HD could enhance appeal further among potential buyers.
Video description

In this episode I look at the performance & features of the Fosi S3 Streamer/Preamp. Here is a link to the S3 on Fosi’s website: https://fosiaudio.com/products/s3-balanced-hifi-streamer?gad_source=1&gad_campaignid=23068834942&gbraid=0AAAAABNZugTqo56gm506Xnx7HKAnCcnv9&gclid=CjwKCAjw8uTQBhAdEiwAVvtJyvVBkUOEeGBO3kV_btO__9_TbT1H8OYWhj224Rcyy_SWycGkl5Qg2RoCL_EQAvD_BwE UPDATE- Fosi's latest firmware/app update (6/17/26) fixed the problem with only showing 31 Files/Folders when viewing the UPnP (NAS) drive! However, using the Search Menu still caused my NAS drive to hang up requiring unplugging the power to it for a few seconds. 00:00 Introduction 04:40 Preamp THD/ SNR & harmonics (Unbalanced inputs & outputs) 05:37 Preamp THD vs Freq & Input Signal Level 06:41 Preamp System Noise 07:10 Preamp Frequency Response 07:49 Preamp Multitone 08:02 IMD 08:25 Crosstalk 08:48 THD/ SNR & harmonics via Streamer (via UPnP) using the Unbalanced outputs 09:48 THD/ SNR & harmonics via Streamer (via UPnP) using the Balanced outputs 11:50 Frequency Response harmonics via Streamer (via UPnP) using the Unbalanced outputs 14:02 Subwoofer Out Freq response 14:29 Volume control changes 15:32 Phase & Risetime 17:08 The S3 App “tour” 21:18 Listening & Final Comments