Pro-Ject Phono Box DS3 B
Pro-Ject phono preamplifier compatible with MM and MC cartridges, featuring balanced XLR connectivity and front-panel impedance and gain settings.
Description
The Pro-Ject Phono Box DS3 B is a phono preamplifier designed for turntables fitted with moving magnet (MM) or moving coil (MC) cartridges. It sits between the turntable and the amplifier to amplify and equalise the phono signal according to the RIAA curve before passing it on to the rest of the hi-fi chain.
The unit is built around passive RIAA equalisation and a dual mono circuit designed to keep the left and right channels separate. Input impedance can be adjusted continuously from 10 to 1000 ohms, or fixed at 47 kOhms, while input capacitance switches between 50, 150, 300 and 400 pF: these settings, accessible on the front panel, allow the preamp to be precisely matched to the electrical characteristics of the cartridge in use. Gain is also adjusted on the front panel across six values from 40 to 65 dB, with an additional 6 dB when the XLR output is used. A subsonic filter at 20 Hz (18 dB/octave) limits infrasonic noise caused by warped records or mechanical resonances. The stated signal-to-noise ratio and harmonic distortion figures, along with a RIAA curve accuracy of under 0.25 dB across the entire audible range, point to a circuit designed to preserve the fine detail of the signal drawn from vinyl.
In terms of connectivity, the unit is notable for a 5-pin mini XLR input, an XLR input and a pair of XLR outputs, in addition to gold-plated RCA inputs and outputs. A 12V trigger input and output (2.5 mm jack) allow the preamp's power-on to be synchronised with that of another component in the chain, such as the amplifier or the turntable. The chassis, built from an aluminium and metal sandwich construction, is designed to limit vibration and electromagnetic interference.
This preamp is aimed at vinyl enthusiasts with a turntable fitted with an MM or MC cartridge who wish to finely tune the behaviour of their phono preamp, particularly via a balanced XLR connection to the amplifier, within a system where careful attention to connectivity and precise adjustment matters as much as listening quality.
Technical specifications
| Input impedance | 10 to 1000 ohms (continuous) or 47 kOhms (fixed) |
| Input capacitance | 50 / 150 / 300 / 400 pF |
| Switchable gain | 40 / 45 / 50 / 55 / 60 / 65 dB (+6 dB with XLR output) |
| Subsonic filter | 20 Hz, 18 dB/octave |
| Signal to noise ratio MM (40 dB) | 104 dBV, 111 dBV |
| Signal to noise ratio MC (60 dB) | 85 dBV, 91 dBV |
| Harmonic distortion (THD) at 1 kHz | < 0.001 % MM and < 0.004 % MC |
| Total harmonic distortion (20 Hz 20 kHz) | < 0.005 % MM and < 0.01 % MC |
| RIAA equalisation curve accuracy | < 0.25 dB / 20 Hz - 20 kHz |
| Power consumption when on | 18V/max. 290 mA DC |
| Power consumption in standby | < 0.5 watt |
| Dimensions (W x H x D) | 206 x 72 x 194 mm |
| Weight | 1.48 kg |
What to check before buying used
On this phono preamplifier, it is worth testing the impedance, capacitance and gain switches on the front panel, as these are mechanical components subject to wear that can oxidise or become imprecise over time. Also check that the XLR inputs and outputs, as well as the trigger connectors, are working properly, as these are less common and sometimes more fragile than RCA. Checking the supplied mains adapter and the stability of the 18V power supply is also recommended.
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