• A More Complete HiFi Amp: Evolved from the proven ST-01 PRO and refined around real HiFi needs, ST-02 combines a DAC, stereo amplifier, and headphone amplifier in a single unit. Bluetooth 5.4, PC-USB, optical, coaxial, and RCA cover both digital and analog sources, with direct lossless playback from USB drives.
• Power Meets Precise 2.1 Control: TPA3255 delivers up to 300W×2 for strong drive with 4–8Ω passive speakers. Post-Filter Feedback (PFFB) keeps frequency response more consistent across speaker loads. Adjustable 20–230Hz HPF reduces deep-bass load on the mains, while a 150Hz LPF SUB OUT feeds a powered subwoofer for cleaner, better-integrated 2.1 sound.
• Tube Warmth Meets Dynamic VU: A custom ECC83 tube stage adds classic warmth and texture, while 180V high-voltage operation keeps musical dynamics more composed. Large VU meters make every swing visible, with AGC adapting meter sensitivity across signal levels, while 34 backlight colors and 10 brightness levels let the display fit your setup.
• More Freedom to Shape Your Sound: Fine-tune bass and treble ±9dB to suit your speakers, room, and music, or switch to BYPASS for a more direct signal path. Four socketed NE5532 op-amps open up more room for sonic exploration, while 3.5mm/4.4mm headphone outputs and switchable headphone/speaker modes keep listening flexible.
• More Thought in Every Detail: The high-clarity TFT keeps key status easy to read, while top controls, remote, and WeChat Mini Program put everyday adjustments within easy reach. Selected audio components and a low-noise power design support clean, stable performance, while the aluminum-alloy chassis adds lasting solidity and a premium feel. 

• Brand: Douk Audio
• Model: ST-02
• Audio Inputs: Bluetooth 5.4 / PC-USB / Coaxial / Optical / RCA / U-Disk
• Audio Outputs: Speaker Output / SUB OUT / 3.5mm and 4.4mm Headphone Outputs
• Maximum Output Power: 300 W × 2 @ 4 Ω
• Speaker Impedance: 4–8 Ω
• SNR: ≥ 103 dB
• THD+N: 0.02%
• Frequency Response: 20 Hz–20 kHz (±0.5 dB)
• RCA Input Sensitivity: 2 V
• Bass / Treble Adjustment: ±9 dB
• HPF Frequency Range: 20 Hz-230 Hz
• SUB OUT Low-Pass Filter: 150 Hz
• Supported Sampling Rates:
        PC-USB: Up to 96 kHz / 24-bit
        Bluetooth/U-Disk: Up to 48 kHz / 24-bit
        Coaxial / Optical: Up to PCM 192 kHz / 24-bit
  
• PC-USB Supported Systems: Windows 10/11, macOS, Android, iOS, HarmonyOS
• Supported U-Disk Formats: MP3 / WAV / FLAC / APE
• Maximum U-Disk Capacity: 32 GB
• Maximum Headphone Output: 130mW / 32Ω
• Headphone Impedance: 16–300Ω
• VU Meter Adjustment: 34 Colors / 10 Brightness Levels
• Power Input: DC 24-48V / ≥ 5A, 5.5 × 2.5 mm
• Dimensions (W × D × H): 210 × 97 × 82 mm / 8.27 × 3.82 × 3.23 in   
• Net Weight: 1.21 kg / 2.67 lb   
• Package Weight: 2.01 kg / 4.63 lb

User Manual of Amplifier ST-02

FAQs

Q: What should I know before using BYPASS mode?
A: In BYPASS mode, the input signal passes through the ST-02 at maximum level. Before enabling BYPASS, lower the volume on your source device to avoid a sudden increase in volume that may damage your hearing or speakers.

Q: Can the 3.5mm and 4.4mm headphone outputs be used at the same time?
A: For the best listening experience, we recommend using only one headphone output at a time.

Q: Why does the ST-02 automatically switch inputs when I insert a USB drive?
A: When a USB drive is inserted, the ST-02 automatically switches to U-disk input. To use another source, simply select the desired input again with the input control.  

Q: Can the op-amps be replaced?
A: Yes. The ST-02 uses 4 socketed op-amps, compatible with common dual op-amps such as OPA2604, OPA2134, and MUSES01. Two of the four sockets also provide sufficient clearance for larger Sparkos and Burson discrete op-amps. 

Q: Can the vacuum tube be replaced?
A: Yes. The ST-02 uses an ECC83 tube tube for both stereo channels and is compatible with models such as 12AX7-S, 12AX7B, 7025, and 12AX7. Always turn off the power before replacing the tube.

Q: What power supply does the ST-02 require?
A: We recommend using the supplied DC 36V/6A power adapter. If using another power supply, choose a high-quality DC 24–48V / ≥5A adapter rated at 5A or higher.

Q: Can I control the ST-02 from my phone?
A: Yes. Open WeChat and search for “多客音频” to access the Mini Program and control the ST-02 from your phone.

Q: Are batteries included for the remote control?
A: No. For shipping safety, the remote control does not include batteries. Please prepare 2 × AAA batteries separately.