A balanced MM/MC phono preamplifier in dual mono layout with fully discrete audio circuitry: it takes two turntables and lets you set impedance, capacitance and gain from the front panel.
Phono Box DS3 B: the balanced circuit
The Phono Box DS3 B brings to the DS3 series the balanced connections Pro-Ject had so far kept for its RS line, borrowing some of the Phono Box RS2's solutions. The gain stage is fully symmetrical and works the same way whether the signal arrives on single-ended RCA or on the balanced inputs, which benefits the signal-to-noise ratio. RIAA equalisation is passive, split into separate sections and built from discrete parts: there are no op-amps anywhere in the audio path.
A cartridge is by nature a balanced generator, but because of the way MM types are wired internally an MC is needed to exploit this kind of connection in full. Over a 5-pin mini XLR lead or ordinary XLR cables the signal reaches the preamplifier in symmetrical form, and interference picked up on the way, from household appliances, wifi, Bluetooth and mains cables, is cancelled. Pro-Ject states that the connection is possible with every one of its turntables that has an RCA, mini XLR or 5P output.
Two inputs can be in use together, and the settings for each stay in memory. Load impedance is varied continuously from 10 to 1000 ohms with a knob, even while a record is playing, so the effect of each value is heard at once; a fixed 47 kohm setting is the alternative. Capacitance (four values from 50 to 400 pF) and gain (six levels from 40 to 65 dB, with 6 dB more from the XLR outputs) are chosen with push buttons. The case is steel clad in aluminium panels; a subsonic filter and trigger sockets complete the picture.
Specifications
- Input impedance: continuously adjustable from 10 to 1000 ohms, or fixed at 47 kohms
- Input capacitance: 50, 150, 300 or 400 pF
- Gain: 40, 45, 50, 55, 60 or 65 dB; 6 dB more from the XLR outputs
- Signal-to-noise, MM at 40 dB: 104 dBV, 111 dBV A-weighted
- Signal-to-noise, MC at 60 dB: 85 dBV, 91 dBV A-weighted
- Distortion (THD) at 1 kHz: under 0.001% MM, under 0.004% MC
- Distortion (THD), 20 Hz to 20 kHz: under 0.005% MM, under 0.01% MC
- RIAA accuracy: deviation below 0.25 dB from 20 Hz to 20 kHz
- Subsonic filter: 20 Hz, 18 dB per octave slope
- Inputs: one 5-pin mini XLR, one XLR pair, one RCA pair
- Line outputs: one RCA pair and one XLR pair
- Trigger: 12 V input and output
- Power: 18 V / 500 mA DC; maximum draw 290 mA, standby under 0.5 W
- Dimensions: 206 x 72 x 194 mm (width, height, depth), 205 mm deep including sockets
- Weight: 1480 g, power supply excluded
- Finishes: black, silver
