Pro-Ject - Phono Box DS3 B Phono Stage

True balanced in and out, dual-mono, fully discrete, six gain settings up to 65dB and stepless 10–1000Ω loading — with RIAA accuracy inside a quarter of a decibel.

A moving-coil cartridge puts out something in the region of 0.3 millivolts. Amplifying that by a factor of nearly two thousand while keeping the noise floor below it is the hardest job in domestic audio, and it is the job the Phono Box DS3 B is built for.

The answer Pro-Ject arrived at is a true balanced, dual-mono, fully discrete circuit. Balanced because the cartridge is a floating differential source and treating it as one rejects common-mode noise the single-ended convention throws away. Dual-mono because the two channels never share a supply rail or a ground return. Discrete because op-amps, however good, impose their own character on a signal this small.

The connections reflect that. There is a 5-pin mini-XLR input for turntables like the X1 B whose tonearms terminate that way, a pair of full-size XLR inputs, and a pair of RCAs. Outputs are XLR and RCA. The XLR wiring is pin 1 ground, pin 2 hot, pin 3 cold, which is the AES convention and will interoperate with any modern balanced preamp. Using the XLR outputs adds 6dB to whichever gain setting you have chosen.

Adjustment is thorough: six gain steps from 40 to 65dB in 5dB increments, stepless impedance from 10 to 1,000Ω plus a fixed 47kΩ for moving-magnet, and four capacitance values. RIAA accuracy is a published 0.25dB across the band, distortion is under 0.001% on moving-magnet, and there is a subsonic filter at 20Hz rolling off at 18dB per octave.

One correction to a claim that circulates about this box: it does not offer Decca, Columbia or Teldec equalisation curves. Pro-Ject publishes RIAA only. If you need alternative curves, that is the RS2, not the DS3 B.

Features

• True balanced, dual-mono, fully discrete circuit
• Balanced input and balanced output — 5-pin mini-XLR, full-size XLR and RCA all provided
• Six gain settings: 40, 45, 50, 55, 60 and 65dB, plus 6dB more when using the XLR outputs
• Stepless 10–1,000Ω moving-coil loading, or a fixed 47kΩ for moving-magnet
• Four input capacitance values: 50, 150, 300 and 400pF
• RIAA accuracy within 0.25dB, 20Hz–20kHz
• Subsonic filter at 20Hz, 18dB per octave

Specifications

• Type: Moving-magnet and moving-coil phono preamplifier, true balanced and dual-mono
• Gain: 40 / 45 / 50 / 55 / 60 / 65dB, plus 6dB when using the XLR outputs
• Input impedance: Stepless 10Ω to 1,000Ω, or fixed 47kΩ
• Input capacitance: 50 / 150 / 300 / 400pF
• Where the controls are: Not published. Pro-Ject does not state in the material we could find whether these are front-panel, rear-panel or underside controls
• Signal-to-noise ratio, MM at 40dB: 104dBV and 111dBV, A-weighted. Pro-Ject publishes both figures without labelling which applies to the RCA output and which to the XLR
• Signal-to-noise ratio, MC at 60dB: 85dBV and 91dBV, A-weighted, published the same unlabelled way
• THD at 1kHz: Less than 0.001% (MM); less than 0.004% (MC)
• THD, 20Hz–20kHz: Less than 0.005% (MM); less than 0.01% (MC)
• RIAA accuracy: Less than 0.25dB, 20Hz–20kHz
• Alternate EQ curves: None. RIAA only — Pro-Ject publishes no Decca, Columbia or Teldec curve for this model
• Subsonic filter: 20Hz, 18dB per octave
• Inputs: 1 x 5-pin mini-XLR, 1 pair XLR, 1 pair RCA
• Outputs: 1 pair XLR, 1 pair RCA
• XLR wiring: Pin 1 ground, pin 2 hot, pin 3 cold
• Circuit: Fully discrete, true balanced, dual-mono
• Channel separation: Not published. Pro-Ject publishes no channel separation or crosstalk figure for any product in the Phono Box or Tube Box range.
• Power supply: External, 18V DC / 500mA. The unit draws a maximum of 290mA; standby under 0.5W
• Dimensions: 206 x 72 x 194 mm (W x H x D); 205mm deep including sockets
• Weight: 1,480g without the power supply
• Country of manufacture: Made in Europe. Pro-Ject does not name a specific country
• Warranty: Two years from date of purchase, extendable to three years by registering the product with Pro-Ject and subscribing to their newsletter. Pro-Ject states that warranty is administered by the local distributor and that terms can vary by region; no separate United States term is published. Coverage requires purchase from an authorised dealer — The ’In Groove is one.