network streamer with AK4499EX DAC

The FIIO S15 is a full-size desktop media streamer built for network streaming, local playback, digital decoding, and preamplifier duties. Its AK4191 and AK4499EX DAC architecture works alongside dual ACCUSILICON femtosecond oscillators, a fully-balanced analog signal path, Android 12, HDMI ARC, extensive digital connectivity, and a 7.84-inch (19.9 cm) color touchscreen.

Full-size all-metal construction

At 16.93 inches (430 mm) wide, the S15 is sized to integrate naturally with full-size home audio components. Its all-metal chassis weighs approximately 12.45 lb (5.65 kg), while stable non-slip feet help limit unwanted vibration.

Large color touchscreen

A 7.84-inch (19.9 cm) automotive-grade color display provides direct access to playback, applications, and system controls. FIIO’s custom landscape interface for Android 12 is optimized for the wide display and includes a tailored version of FiiO Music, visual VU meters, and a customizable home screen.

Low-noise linear power supply

A 35W linear power supply uses a custom low-noise transformer and four 4700μF ELNA audio capacitors. Separate digital and analog power supplies reduce interaction between circuit sections, while multiple precision LDO regulators provide secondary regulation throughout the analog stage.

Flexible streaming and playback

The S15 supports third-party Android applications, AirPlay, DLNA, Bluetooth reception, and playback from NAS, LAN, and cloud storage through protocols including UPnP, SMB, and WebDAV. Local libraries can be accessed from internal storage, microSD cards, USB storage devices, portable drives, and an M.2 SSD installed in the supplied drive cage. Roon Ready certification was listed as in progress in the supplied product information.

Precision digital clocking

Two screened ACCUSILICON AS318-B series femtosecond oscillators operate at 45.1584MHz and 49.1520MHz. Their ultra-low phase-noise design helps maintain accurate clocking for decoding and digital output.

Digital audio purification

FIIO’s DAPS digital audio purification system combines a customized Android audio core with a low-jitter clock coprocessor. It enables system-level and application-level playback without forced resampling while matching the clocking requirements of PCM and DSD material.

Flagship AKM conversion

The S15 pairs an AK4191 digital processing stage with the AK4499EX DAC. This architecture separates digital and analog processing and incorporates AKM DWA Routing Technology to help reduce noise while supporting high signal-to-noise performance.

Fully-balanced analog architecture

The analog path remains fully-balanced from DAC conversion through the preamplifier stage. OPA1612 low-noise precision op-amps are used in the I/V and low-pass-filter sections, while both RCA and XLR connections support fixed line output or variable preamplifier operation.

High-performance processing platform

A Qualcomm Snapdragon 660 platform with 4GB of RAM and 64GB of internal storage runs the Android-based interface. The XMOS 16-core XU316 USB controller supports USB DAC decoding up to 768kHz/32-bit PCM and native DSD512.

Bluetooth connectivity

Bluetooth reception supports SBC, AAC, aptX, aptX LL, aptX HD, aptX Adaptive, and LDAC. Bluetooth transmission supports AAC, SBC, aptX, aptX HD, LDAC, and LHDC. The supplied Bluetooth remote provides playback, volume, favorites, and gesture-based navigation controls.

HDMI ARC integration

HDMI 2.0 input and output expand the S15 beyond music-only systems. HDMI decoding supports up to 192kHz/24-bit audio, while HDMI ARC accepts 44.1kHz and 48kHz signals from compatible displays.

Extensive digital connectivity

Digital connections include coaxial, optical, AES, USB Audio, HDMI, and configurable I2S output. The I2S connection offers four selectable pin arrangements for compatibility with different downstream components. Coaxial and AES outputs use digital isolation transformers to improve electrical isolation and reduce ground-loop interference.

Adjustable parametric equalization

A 10-band PEQ operates across the S15’s available operating modes. FIIO’s PEQ interface provides control over frequency, gain, bandwidth, and Q value for system tuning or frequency-response adjustment.

Product highlights

• AK4191 and AK4499EX flagship DAC combination
  
• Dual ACCUSILICON AS318-B femtosecond oscillators
  
• Fully-balanced analog audio architecture
  
• Android 12 with FIIO custom landscape interface
  
• 7.84-inch (19.9 cm) automotive-grade color touchscreen
  
• 35W low-noise linear power supply
  
• XMOS XU316 USB audio controller
  
• USB DAC support up to 768kHz/32-bit PCM and native DSD512
  
• Bluetooth reception with LDAC and aptX Adaptive support
  
• AirPlay and DLNA network streaming
  
• NAS, LAN, microSD, USB storage, and M.2 SSD playback
  
• HDMI 2.0 input and output with HDMI ARC
  
• RCA and XLR line and preamplifier outputs
  
• 10-band parametric EQ
  
• Bluetooth remote control included

Specs

• Operating system: Android 12 with custom landscape display system
  
• Processor: Qualcomm Snapdragon 660
  
• Memory: 4GB RAM
  
• Internal storage: 64GB ROM, approximately 46GB available
  
• Storage expansion: M.2 SSD and microSD card slot
  
• DAC: AK4191 and AK4499EX
  
• USB controller: XMOS XU316
  
• Display: 7.84 inches (19.9 cm)
  
• Colors: Black or silver
  
• Dimensions: Approximately 16.93 × 10.81 × 3.52 inches (430 × 274.5 × 89.5 mm)
  
• Weight: Approximately 12.45 lb (5.65 kg)
  
• Bluetooth transmission: Bluetooth 5.0 with AAC, SBC, aptX, aptX HD, LDAC, and LHDC
  
• Bluetooth reception: Bluetooth 5.1 with SBC, AAC, aptX, aptX LL, aptX HD, aptX Adaptive, and LDAC
  
• Native decoding: Up to 384kHz/32-bit PCM and native DSD256
  
• USB DAC decoding: Up to 768kHz/32-bit PCM and native DSD512
  
• Coaxial input: Up to 192kHz/24-bit
  
• AES input: Up to 192kHz/24-bit
  
• Optical input: Up to 96kHz/24-bit
  
• HDMI input: Up to 192kHz/24-bit
  
• USB Audio output: Up to 768kHz/32-bit and DSD512 with DoP, D2P, and native support
  
• Coaxial output: Up to 384kHz/24-bit and DSD128 with D2P or DoP
  
• Optical output: Up to 192kHz/24-bit
  
• AES output: Up to 384kHz/24-bit and DSD128 with D2P or DoP
  
• HDMI output: Up to 192kHz/24-bit
  
• RCA preamplifier output: L+R 4.5Vrms+4.5Vrms at 1kHz into 10kΩ
  
• XLR preamplifier output: L+R 8.9Vrms+8.9Vrms at 1kHz into 10kΩ
  
• RCA line output: L+R 2.4Vrms+2.4Vrms at 1kHz into 10kΩ
  
• XLR line output: L+R 4.8Vrms+4.8Vrms at 1kHz into 10kΩ
  
• Frequency response: 20Hz to 70kHz, attenuation below 2.8dB
  
• Signal-to-noise ratio: At least 131dB A-weighted
  
• Line-output noise floor: Below 1.8μV A-weighted
  
• THD+N: Below 0.00023% at 1kHz, 0dB into 10kΩ

What’s included

• FIIO S15
  
• Bluetooth remote control
  
• AC power cord
  
• M.2 SSD cage
  
• USB 3.0-compatible HDD cage data cable
  
• HDD cage installation screwdriver
  
• Spare fuse
  
• 3.5mm audio cable
  
• USB-A dust plug
  
• USB-C dust plug
  
• Warranty card
  
• Quick start guide
  
• HDD cage instruction manual
  
• Remote control diagram