A phono preamplifier for MM and MC cartridges built around a balanced circuit from input to output, with 5-pin mini XLR and RCA inputs, XLR and RCA outputs, and loading and gain set from the front panel.
Phono Box S3 B: the balanced circuit
The balanced connection that Pro-Ject had so far kept for its RS series arrives here in a compact chassis. A cartridge is a balanced generator by its very construction: link the turntable with a 5-pin mini XLR lead and the signal travels on two mirrored legs, so the gain stage can reject whatever noise was picked up on the way from domestic appliances, Wi-Fi networks and mains leads. Getting the whole benefit calls for an MC cartridge, because the internal wiring of MM types does not allow it to the same degree.
The amplifying section is symmetrical and assembled from individual parts, with no integrated circuits, and it hands a clean signal to the RIAA equalisation network, which is of the semi-passive kind. Two turntables can stay connected, one per input, and the unit keeps the settings of each in memory. A subsonic filter acts at 20 Hz with a slope of 18 dB per octave.
Front-panel buttons select impedance (10 ohms to 47 kohms), capacitance (50 to 400 pF) and gain (40 to 65 dB, with a further 6 dB on the XLR outputs): enough to suit the preamplifier to the cartridge and to bring the turntable level in line with a CD player or a streamer. The steel and aluminium enclosure is stiff and keeps outside interference away from the circuit. The power supply is a separate 18 V unit.
Specifications
- Type: balanced MM/MC phono preamplifier
- Input impedance: 10, 50, 100 ohms, 1 kohm, 47 kohms
- Input capacitance: 50, 150, 300, 400 pF
- Gain: 40, 45, 60 or 65 dB (6 dB more from the XLR outputs)
- S/N ratio, MM at 40 dB: 103 dBV, 110 dBV A-weighted
- S/N ratio, MC at 60 dB: 85 dBV, 90 dBV A-weighted
- Distortion at 1 kHz: below 0.001% (MM) and 0.005% (MC)
- Distortion 20 Hz - 20 kHz: below 0.008% (MM) and 0.01% (MC)
- RIAA accuracy: within 0.3 dB from 20 Hz to 20 kHz
- Subsonic filter: 20 Hz, 18 dB per octave
- Inputs: one 5-pin mini XLR, one RCA pair
- Line outputs: one RCA pair, one XLR pair
- Power supply: external, 18 V / 500 mA DC
- Consumption: 170 mA at 18 V; standby under 0.5 W
- Size (WxHxD): 206 x 55 x 153 mm, 164 mm including sockets
- Weight: 930 g, power supply excluded
- Finishes: silver, black
