Pro-Ject Phono Box S2 Phono Stage (Silver)

The Pro-Ject Phono Box S2 is an MM/MC phono preamplifier from Pro-Ject's S Line — the company's mid-range Box Design series, developed and engineered in Vienna, Austria. It sits below the fully discrete Phono Box S2 Ultra in the range hierarchy, offering a dual mono circuit topology with audiophile-grade components at a more accessible price point.

Circuit Design & Construction

The Phono Box S2 employs a dual mono amplification layout, which separates the left and right channels through independent signal paths to optimise stereo imaging and minimise crosstalk. The RIAA equalisation stage uses audiophile-grade WIMA polypropylene capacitors, chosen for their low dielectric absorption and tight tolerances. RIAA accuracy is specified at less than 0.4dB across the full 20Hz–20kHz audible range.

The chassis uses an aluminium and metal sandwich construction that serves as both an electromagnetic shield and a vibration-damping enclosure. This is particularly important for a phono stage, where the very low signal levels from a cartridge make the circuit susceptible to interference from nearby power supplies, transformers, and digital equipment.

Cartridge Compatibility & Adjustment

The Phono Box S2 supports both moving magnet (MM) and moving coil (MC) cartridges, with extensive adjustment via DIP switches on the underside of the unit. Four gain settings are available: 40dB and 43dB for MM cartridges, and 60dB and 63dB for low-output MC designs. Input impedance is switchable between 10Ω, 100Ω, and 1kΩ for MC cartridges, with MM cartridges operating at the standard 47kΩ. Input capacitance can be set to 100pF, 200pF, 320pF, or 420pF for MM and high-output MC cartridges — input capacitance is irrelevant for low-output MC cartridges and can be left at any setting.

This range of adjustment makes the Phono Box S2 compatible with almost any modern cartridge. The user manual includes worked examples for popular cartridges including the Ortofon 2M Red (MM), Ortofon X5-MC (high-output MC), and Ortofon Rondo Red (low-output MC).

Subsonic Filter & Noise Performance

A switchable subsonic filter is accessible via a toggle on the rear panel, rolling off at 20Hz with a slope of 12dB per octave. This is useful for taming low-frequency rumble from warped records or turntable bearing noise without affecting audible bass content.

The signal-to-noise ratio is specified at 94dB (A-weighted) when operating at MM gain settings (40/43dB), dropping to 75dB at MC gain levels (60/63dB) — consistent with the higher amplification required for low-output cartridges. Total harmonic distortion is less than 0.01% at MM gain and less than 0.05% at MC gain.

Power & Connectivity

Power is supplied via an external 18V DC adapter (500mA, included), keeping the mains transformer and its associated magnetic field away from the sensitive phono circuitry. Standby power consumption is less than 1W. A front-panel button with a blue LED indicator toggles between active and standby modes.

Connections are straightforward: one pair of gold-plated RCA phono inputs and one pair of RCA outputs, plus a ground terminal for the turntable’s earthing wire. The output connects to any line-level input (AUX, CD, Tuner, or Tape) on an amplifier. The power supply can optionally be upgraded to the Pro-Ject Accu Box S2 battery supply for further noise reduction.