Pro-Ject Tube Box S2 Tube Phono Preamplifier

Fully Discrete Circuit · Replaceable Vacuum Tubes · Warm Musicality · Entry-Level Tube Flagship

The Pro-Ject Tube Box S2 is the brand's first fully discrete (op-amp-free) tube phono preamplifier, featuring two replaceable ECC83 (12AX7) vacuum tubes, delivering a rich, warm, and relaxed sound signature. It supports MM and MC cartridges and offers front panel gain and subsonic filter controls, as well as extensive load adjustments, making it almost perfectly compatible with most cartridges on the market.

Compact and exquisite, with a sound rich in tube charm, it is an ideal entry-level high-end choice for those who want to experience true tube sound quality.

Product Basic Information

• Type: Tube MM / MC Phono Preamplifier
• Tubes: 2 × ECC83 (12AX7A), replaceable (supports tube rolling)
• Supported Cartridges: MM (Moving Magnet) and MC (Moving Coil)
• Adjustments: Front panel gain and subsonic filter; bottom DIP switch for load adjustment
• Output: RCA Line Level Output
• Color: Black or Silver
• Origin: Hand-made in Europe
• Accessories: External 18V DC power supply

Core Technology Highlights

• Fully Discrete Circuit Design: No Op-Amps used at all, resulting in a more natural and pure sound
• Replaceable Vacuum Tubes: Supports tube rolling, allowing users to customize the sound character to their preference
• Hybrid Architecture: FET input stage + tube gain stage, balancing low noise and tube warmth
• Dual Mono Design: Excellent channel separation and soundstage performance
• Accurate RIAA Equalization: Passive/active two-stage equalization, with a maximum deviation of only 0.4dB
• Front Panel Control: One-button operation for gain switching and subsonic filtering
• Adjustable Input Impedance and Capacitance: 10 / 100 / 1k / 2kΩ, etc.; multiple capacitance options
• Aluminum/Metal Sandwich Chassis: Effectively shields against electromagnetic interference and vibration
• High-Quality Power Filtering: Independent high-voltage anode power supply to reduce interference

Detailed Specifications

• Tubes: 2 × ECC83 (12AX7A)
• Input Impedance: 10Ω / 100Ω / 1kΩ / 2kΩ (also fixed 47kΩ)
• Input Capacitance: 47 / 147 / 267 / 367 / 487 / 587 pF
• Gain: 40 / 43 / 50 / 60 / 63 dB
• Signal-to-Noise Ratio: Approx. 75–80 dB (A-weighted)
• Total Harmonic Distortion: <0.02%–0.05%
• RIAA Accuracy: 20Hz–20kHz / max. ±0.4dB
• Subsonic Filter: 20Hz / 18dB/octave
• Input / Output: 1 set of RCA each
• Power: External 18V / 1000mA DC
• Power Consumption: Approx. 470mA (standby <1W)
• Dimensions: 103 × 73 × 131 mm
• Weight: Approx. 410g (without power supply)

Sound Performance and Characteristics

The Tube Box S2 delivers the warm, rich, and relaxed sound typical of tube phono stages. The mid-range is particularly smooth and full-bodied, with excellent vocal and instrument textures, and an open and spacious soundstage with stable, uncompressed dynamics. The background is relatively quiet, with sufficient detail, presenting an overall easy-listening, enduring, and musical performance.

The replaceable vacuum tubes allow users to further fine-tune the sound character, making it a highly attractive choice for entry-level tube systems.

Online Reviews

• Users and Media: Warm and rich sound, excellent mid-range, good dynamics and spaciousness, a "true tube phono stage."
• Reviews: Good performance out of the box, supports tube rolling, high cost-effectiveness, suitable for users who want to experience tube warmth.
• Several reviewers praise its "compact size yet full of tube charm," significantly enhancing the musicality of a vinyl system.