Pro-Ject - Tube Box DS3 B Phono Stage

The balanced, dual-mono DS3 B chassis with a pair of E88CC valves in it: 5-pin mini-XLR, XLR and RCA inputs, XLR and RCA outputs, six gain settings to 65dB and stepless moving-coil loading.

Tube Box DS3 B is the valve sibling of the Phono Box DS3 B, and it inherits the whole connection set: a 5-pin mini-XLR input for balanced tonearms, a pair of full-size XLR inputs, a pair of RCAs, and both XLR and RCA outputs. Balanced in, balanced out, dual-mono throughout. The gain ladder is the same six steps from 40 to 65dB, with 6dB more available from the XLR outputs.

The valves are E88CC double triodes, also written 6922 — a frame-grid tube with lower noise and lower impedance than the ECC83 used in the Tube Box S2, and a more natural fit for a design that also has to handle a balanced signal path. They sit in sockets.

Loading is stepless from 10 to 1,000Ω for moving coil, with a fixed 47kΩ position for moving-magnet, and four capacitance values from 50 to 400pF. A 5mV input at the 40dB setting produces 500mV out. RIAA accuracy is ±0.5dB, which is looser than the solid-state DS3 B’s ±0.25dB — that is a normal and expected consequence of a valve gain stage, not a defect.

Unlike the Tube Box S2, Pro-Ject’s web page and PDF datasheet for this model agree with each other on every figure we checked. The newer documentation is simply better maintained.

Features

• Two E88CC / 6922 valves, socketed
• True balanced, dual-mono topology with balanced input and output
• 5-pin mini-XLR, full-size XLR and RCA inputs; XLR and RCA outputs
• Six gain settings from 40 to 65dB, plus 6dB from the XLR outputs
• Stepless 10–1,000Ω moving-coil loading, or fixed 47kΩ for moving-magnet
• Four input capacitance values: 50, 150, 300 and 400pF
• Subsonic filter at 20Hz, 18dB per octave

Specifications

• Type: Valve moving-magnet and moving-coil phono preamplifier, true balanced and dual-mono
• Valves: 2 x E88CC (6922), socketed. Pro-Ject does not explicitly market valve rolling as a supported feature
• 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
• Output level: 500mV at 1kHz for a 5mV / 1kHz input at the 40dB setting
• Signal-to-noise ratio: Greater than 87dBV, A-weighted. Pro-Ject publishes one figure and does not split it by MM and MC
• THD: Less than 0.03%
• RIAA accuracy: ±0.5dB, 20Hz–20kHz
• Alternate EQ curves: None. RIAA only
• 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
• 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 / 1,000mA
• Dimensions: 206 x 70 x 194 mm (W x H x D)
• Weight: 1,560g 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.