The Head Box E is a headphone amplifier built from discrete components, with an RCA input and two front outputs, 6.3 and 3.5 mm, that can run together: it delivers 665 mW into 32 ohms, enough even for headphones that are hard to drive.
Head Box E: what is inside
Headphone outputs on laptops and smartphones are short of power and do not get the most out of current headphones. The Head Box E connects to a source through its RCA input and makes 665 mW available into 32 ohms, with 11 dB of gain and an output impedance under 1 ohm. The front carries a 6.3 mm jack for hi-fi headphones and a 3.5 mm one for newer headphones and earphones: two people can listen at once.
The amplifier stage is discrete throughout, with no integrated chips: a choice that, according to the manufacturer, gives good measurements, with distortion plus noise below 0.005% and a response from 20 Hz to 80 kHz, and that keeps servicing and repair straightforward over the years. At the rear two further RCA sockets pass the input signal back out, so the Head Box E slots between the source and an amplifier without taking up a connection.
The case is metal all round, shielding against electromagnetic interference and vibration, with a front panel and controls in machined aluminium. Power is 5 V / 0.5 A DC; as an upgrade the manufacturer lists the Accu Box S2 and Accu Box S2 USB supplies as compatible. It works with headphones from 8 to 600 ohms. It measures 103 x 37 x 120 mm and weighs 390 g.
Specifications
- Type: discrete headphone amplifier
- Power output: 665 mW with a 32 ohm load
- Gain: 11 dB
- Output impedance: under 1 ohm
- Signal/noise: -105 dBV
- Distortion plus noise: below 0.005%
- Crosstalk: 65 dB
- Frequency range: 20 Hz - 80 kHz (+/- 0.02 dB)
- Analogue in: two RCA sockets
- Headphone outs: 6.3 mm jack plus 3.5 mm jack, both live together
- Loop out: two RCA sockets for an amplifier
- Suitable headphones: impedance between 8 and 600 ohms
- Power: 5 V / 0.5 A DC
- Standby draw: under 0.5 W
- Size (width x height x depth): 103 x 37 x 120 mm overall
- Weight: 390 g, adaptor excluded
- Finishes: black, silver
