Фонокорректоры — Pro-Ject Tube Box S3 B

The Tube Box S3 B is a Pro-Ject Audio Systems phono preamp of the S3 range that adds valves to a balanced layout, built around a symmetrical discrete gain stage with a balanced 5-pin mini XLR input and balanced XLR outputs. Both MM and MC pickups are supported, the preamp is made by hand in the EU, and the casing is offered in two colours, silver and black.

Key specs that matter

Two ECC83 tubes, also known as 12AX7, are part of the circuit. Input impedance choices are 10, 50, 100, 1k and 47k ohm, and capacitance can be set to 50, 150, 300 or 400 pF. Gain settings run 40, 45, 60 and 65 dB, and the XLR outputs add 6 dB on top. The quoted signal-to-noise figure is 97 or 105 dBV A-weighted for MM and 83 or 88 dBV A-weighted for MC. At 1 kHz total harmonic distortion is below 0.005 percent for MM and 0.01 percent for MC, while across 20 Hz to 20 kHz the figures are below 0.1 and 0.03 percent. RIAA accuracy is within 0.4 dB from 20 Hz to 20 kHz. The unit measures 206 x 81 x 153 mm, with sockets adding depth to 164 mm, and weighs 1010 g when measured without the power supply.

Engineering and use context

The balanced design runs two signal chains, hot and cold, so interference that enters both along the way cancels out rather than being amplified. Pro-Ject names this True Balanced Connection and designs it to work with its own balanced phono cables. The input section offers one 5-pin mini XLR socket and one RCA pair, and the output section offers a single RCA pair plus a single XLR pair. A subsonic filter at 20 Hz with an 18 dB per octave slope removes the lowest frequencies below the audio band. The casework is steel and aluminium, and power comes from an external 18 V DC supply rated at 800 mA, compared with 500 mA for the solid-state S3 B model. The case is 26 mm taller than that solid-state sibling, giving room for the two tubes.

Pairing

The load options cover cartridges from low-output moving-coil types to moving-magnet designs. A turntable wired with a balanced 5-pin arm cable uses the symmetrical input, and the XLR outputs can connect to a preamplifier, integrated amplifier or active speakers with balanced inputs, with the RCA outputs covering conventional line inputs. The wide gain range, plus the extra boost via XLR, lets the stage be set to the output level of the cartridge in use.

Alternatives

The Pro-Ject Phono Box S3 B offers the same load and gain options with a transistor-only circuit in a 55 mm tall case.