Pro-Ject Tube Box E black

Pro-Ject Tube Box E: tube phono preamp

A tube phono preamp in a 103 mm-wide enclosure, compatible with MM and MC, with a discrete circuit without an operational amplifier and replaceable tubes: the Tube Box E takes the design principles of the Tube Box S2 and brings them to Pro-Ject’s E range, the most affordable in the Box Design catalog. It is the first tube phono preamp in this series.

A circuit inherited from the Tube Box S2, in a reduced format

The Tube Box E borrows its topology from the Tube Box S2, which remains in the catalog. The circuit is fully discrete, without an operational amplifier (OpAmp), and is based on a field-effect transistor (FET) input stage followed by an ECC83 tube output stage. Pro-Ject has revised the choice of certain components and opted for a more compact chassis to reach a lower price point, but the design philosophy remains identical: dual mono for channel separation, polystyrene capacitors in critical positions, RIAA equalization combining passive and active filtering, and a high-voltage anodic power supply with reinforced filtering.

The absence of OpAmps has a practical consequence that is often overlooked: repairability. A discrete circuit can be diagnosed and repaired component by component, which extends the useful life of the device well beyond what one would expect from a product in this price range.

Two replaceable ECC83s, and all that it implies

The two ECC83 tubes (also known by the 12AX7A reference) are mounted on standard pin sockets, accessible without opening the enclosure. They can be replaced in the event of wear, but also swapped for other brands or variants (tube rolling) to influence the sonic character. A vintage Mullard tube will not sound like a new JJ Electronic, and that is precisely the point: the Tube Box E leaves room for customization that solid-state preamps do not offer.

Pro-Ject describes the sound reproduction as warm, with generous mids and a relaxed presentation, typical of a tube output stage. This manufacturer characterization should be qualified according to the cartridge, cabling, and tubes used, but the “tube” sonic tendency is clearly present in the design.

MM and MC compatibility with extensive adjustments

The Tube Box E’s versatility with cartridges is one of its most concrete strengths. Six gain levels are accessible from the front panel (40, 43, 50, 53, 60, and 63 dB), covering both standard MM cartridges and low-output MC cartridges. The load settings, meanwhile, are located underneath the device:

• Input impedance: 10, 100, 1k, or 2k ohms (for MC cartridges)
• Load capacitance: 47, 147, 267, 367, 487, or 587 pF, plus 47k ohms (for MM cartridges and high-output MC cartridges)

This number of load options is uncommon at this price level. It allows precise matching with most cartridges on the market, without compromise in impedance or capacitance matching.

A front-panel subsonic filter

The subsonic filter button, directly accessible on the front panel, cuts at 20 Hz with a slope of 18 dB per octave. Its usefulness depends on the context: with a tonearm or turntable sensitive to low-frequency resonances, or in a room where infrabass causes problems, it cleans up the signal without affecting the audible band. On a well-damped setup, it can be left disabled. The choice is there, and it can be made without turning the device over.

Compact construction, metal shielding

At 103 × 73 × 115 mm (131 mm including connectors) and 450 g without the power supply, the Tube Box E is one of the most compact tube phono preamps on the market. The enclosure is entirely metal, ensuring shielding against electromagnetic interference and mechanical protection against vibrations. The front panel and control elements are made of machined aluminum, in the characteristic style of the Box Design series. The device is offered with a silver or black front panel.

Connectivity is limited to one pair of gold-plated RCA inputs and one pair of outputs. There is no balanced output here (you need to move up to the Tube Box S3 B for that), and no dual input either: the Tube Box E handles a single source.

The power supply is external (18 V / 1 A DC), a classic choice in this range that keeps the transformer away from the audio circuit. Power consumption is 470 mA in operation and less than 1 W in standby.

Technical specifications

Cartridge compatibility

• Compatible with MM and MC cartridges
• Extended loading options adjustable underneath the unit for precise matching with the cartridge

Circuit and amplification

• Fully discrete design, without operational amplifiers (OpAmps)
• Very low-noise circuitry with FET input stage
• Dual mono architecture for optimized channel separation
• Precision passive and active RIAA equalization
• Polystyrene capacitors used wherever possible
• Multiple internal power supplies
• Heavily filtered high-voltage anode power supply
• Tube complement: 2x ECC83 (12AX7A), replaceable (tube rolling possible)

Settings and controls

• Front-panel subsonic filter button
• Front-panel gain adjustment
• Gain: 40, 43 dB B / 50, 53 / 60, 63 dB A
• Input impedance: 10 / 100 / 1k / 2k ohms A
• Capacitance: 47 / 147 / 267 / 367 / 487 / 587 pF / 47k ohms B
  • A: typical for low-output MC cartridges
  • B: typical for MM or high-output MC cartridges

Audio performance

• Noise floor
  • 77 dB (A-weighted) at an input gain of 40 dB
  • 65 dB (A-weighted) at an input gain of 50 dB and 63 dB
• THD
  • < 0.03% at an input gain of 40 dB
  • < 0.07% at an input gain of 50 dB and 63 dB
• RIAA curve accuracy: +/- 0.5 dB / 20 Hz - 20 kHz
• Subsonic filter: 20 Hz at 18 dB / octave

Connectivity

• Input / output: 1x RCA / 1x RCA
• Gold-plated input and output RCA connectors

Power supply

• External power supply: 18 V / 1 A DC
• Consumption: 470 mA DC, < 1 W in standby

Construction and design

• Full metal enclosure for effective protection against electromagnetic interference and vibrations
• Machined aluminum front panel and control elements
• Color options: silver or black front panel

Dimensions and weight

• Dimensions (w x h x d): 103 x 73 x 115 (131) mm (with connectors)
• Weight: 450 g without power supply