The Tube Box E is a valve phono preamplifier for MM and MC cartridges, with two replaceable ECC83s, a dual-mono circuit free of op-amps and gain, impedance and capacitance settings to match it to the cartridge.
Tube Box E: valves and settings
It brings the layout of Pro-Ject's valve phono stages into the E range in a reduced format. The circuit is discrete throughout and uses no operational amplifiers: the input stage is a low-noise FET design, RIAA equalisation is split into two parts, one passive and one active, and the output is entrusted to two ECC83 (12AX7A) valves. Each channel has its own circuit, which benefits stereo separation, and polystyrene capacitors are fitted wherever practical.
Cartridge matching is broad. From the front you choose among five gain levels, 40, 43, 50, 60 and 63 dB, and engage the subsonic filter, which acts at 20 Hz with an 18 dB per octave slope. Loading is set underneath the unit: impedance of 10 ohms, 100 ohms, 1 kohm or 2 kohms, or else 47 kohms with capacitance selectable across six values between 47 and 587 pF.
The valves can be swapped by anyone wishing to try other ECC83s and alter the character of the sound, which the manufacturer describes as full and relaxed with a rich midrange. The internal power supply is divided into several sections, with a well-filtered anode voltage; the external adaptor is rated at 18 V / 1,000 mA. The metal case guards against interference and vibration, the front and controls are machined aluminium, and the RCA inputs and outputs are gold-plated.
Specifications
- Type: valve phono stage for MM and MC cartridges
- Valves: two ECC83 (12AX7A), replaceable
- Circuit: discrete dual mono, FET input, no op-amps
- Gain: 40, 43, 50, 60 and 63 dB, set from the front
- Input load: 10 ohms, 100 ohms, 1 kohm, 2 kohms or 47 kohms
- Input capacity: 47, 147, 267, 367, 487 and 587 pF
- Noise floor: 77 dB (A) with 40 dB gain; 65 dB (A) with 50 and 63 dB
- Harmonic distortion: under 0.03% with 40 dB gain; under 0.07% with 50 and 63 dB
- RIAA accuracy: +/- 0.5 dB from 20 Hz to 20 kHz
- Subsonic filter: 20 Hz, 18 dB per octave
- Input: two gold-plated RCA sockets
- Line out: two gold-plated RCA sockets
- Power: external adaptor, 18 V / 1,000 mA DC
- Current draw: 470 mA DC, under 1 W at idle
- Size (width x height x depth): 103 x 73 x 131 mm, sockets included
- Weight: 450 g, adaptor excluded
- Finishes: black, silver
