Pro-Ject Phono Box S3 B
MM/MC phono preamplifier with Dual Mono construction, fitted with XLR and RCA outputs and multiple impedance and gain settings, for amplifiers equipped with a line input.
Description
The Pro-Ject Phono Box S3 is an external phono preamplifier designed to match the signal from an MM or MC cartridge to the line input of an amplifier. It succeeds the Phono Box S2 and builds on the same foundation, while adding full balanced connectivity.
The unit stands out for the addition of a 5-pin mini XLR input and a pair of XLR outputs, alongside the standard RCA inputs and outputs. This balanced connection limits interference along the signal path and provides an additional 6 dB of gain when used on the output. Gain is switchable across four values (40, 45, 60 or 65 dB), input impedance is adjustable across five positions and input capacitance across four values, allowing the unit to be precisely matched to the type of cartridge used, MM or MC. A subsonic filter at 20 Hz (18 dB/octave) removes infrasonic frequencies linked to record warp, while the Dual Mono construction and audiophile-grade amplification modules aim to limit noise and distortion across the entire audio spectrum.
This preamplifier is aimed at turntable users with an MM or MC cartridge, wishing to connect their turntable to an amplifier lacking a phono input or fitted with balanced XLR inputs. Its versatile settings make it suitable for both an entry-level setup and a more demanding system making use of the XLR connection.
Technical specifications
| Input impedance | 10 / 50 / 100 / 1000 / 47 000 ohms |
| Input capacitance | 50 / 150 / 300 / 400 pF |
| Switchable gain | 40 / 45 / 60 / 65 dB (+6 dB with XLR output) |
| Subsonic filter | 20 Hz, 18 dB/octave |
| Signal to noise ratio MM (40 dB) | 103 dBV, 110 dBV |
| Signal to noise ratio MC (60 dB) | 85 dBV, 90 dBV |
| Harmonic distortion (THD) at 1 kHz | < 0.001% MM and < 0.005% MC |
| Total harmonic distortion (20 Hz 20 kHz) | < 0.008% MM and < 0.01% MC |
| RIAA equalisation curve accuracy | < 0.3 dB / 20 Hz - 20 kHz |
| Connections | 1 x 5-pin mini XLR input, 1 x pair of RCA inputs, 1 x pair of RCA outputs, 1 x pair of XLR outputs |
| Power supply | External power supply unit 18 V DC/500 mA, mains voltage 220-230 V/50-60 Hz |
| Power consumption | 18 V/170 mA DC |
| Standby consumption | < 0.5 W |
| Dimensions (w x h x d) | 206 x 55 x 153 mm |
| Weight | 930 g net (without power supply unit) |
What to check before buying used
For this phono preamplifier, checks focus above all on the external 18 V DC/500 mA power supply unit, which is often lost or replaced over successive resales: make sure it is either the original model or a compatible equivalent in terms of voltage and current. It is worth testing the RCA and 5-pin mini XLR inputs in turn, along with both outputs, to rule out any contact fault on lightly used connectors. Checking the gain, impedance and input capacitance switches also allows you to confirm that they switch correctly across all their positions.
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