The Head Box S2 Digital combines a D/A converter with a headphone amplifier: three digital inputs (USB, coaxial, optical), an ESS9038Q2M chip, PCM as high as 32-bit / 768 kHz and DSD256 over USB, and a 6.3 mm headphone socket on the front.
Head Box S2 Digital: inputs and conversion
Anyone listening on headphones from a computer, a television or a CD transport gets conversion and amplification in one case here. The type B USB port takes PCM as high as 32-bit / 768 kHz and DSD up to DSD256, carried as DSD over PCM; the optical and coaxial inputs reach 24-bit / 192 kHz. The former is meant for a television, the latter for a digital transport, the CD Box DS2 T for instance.
Conversion is handled by a 32-bit ESS Sabre ESS9038Q2M. Around it Pro-Ject has built its own clock circuit, with every internal oscillator synchronised and a quoted jitter of 100 femtoseconds, organic polymer capacitors, thin-film miniMELF resistors and a four-layer circuit board with gold-plated tracks. Five digital filters can be chosen from the front panel, and the maker also cites a filter of its own tuned for transient response.
The 6.3 mm headphone output delivers 68 mW into 32 ohms and 6.6 mW into 600 ohms; at the rear there is a 2.05 V RCA pre-out for connecting an amplifier. Noise arriving over USB is filtered twice before it reaches the audio section. The aluminium and metal sandwich case guards against vibration and interference, and the external 5 V, 1 A power supply comes in the box.
Specifications
- Type: D/A converter with headphone amplifier
- Dynamic range: 120 dBA
- Digital inputs: USB type B, coaxial RCA, optical Toslink
- Converter chip: 32-bit ESS9038Q2M
- Formats over USB: PCM to 32-bit / 768 kHz, DSD to DSD256
- Formats on coaxial and optical: PCM to 24-bit / 192 kHz
- Digital filters: 5, chosen on the front panel
- Bandwidth: 20 Hz to 20 kHz
- Outputs: 6.3 mm headphone socket at the front, RCA pre-out
- Output voltage: 2.05 V RMS
- Headphone power: 68 mW into 32 ohms, 6.6 mW into 600 ohms
- Harmonic distortion: 0.0007 % (0 dB level, 2 V RMS, 1 kHz)
- External power supply: 5 V DC, 1 A, supplied
- Weight: 360 g, power supply excluded
- Size (width x height x depth): 103 x 37 x 122 mm with knob and sockets
- Finishes: black, silver
