Усилители для наушников — Pro-Ject Head Box S2

The Head Box S2 is a compact Pro-Ject headphone amp, part of the brand's S2 range of small-footprint components. It takes an analogue line signal and drives headphones through two front outputs, and Pro-Ject presents it as suitable for demanding headphones, with superior low distortion listed among its main features. The small footprint lets it fit on a crowded desk or inside a rack next to other S2 components. Two case colours exist, silver and black.

Key specs that matter

Output power is rated at 725 mW into 32 ohms, and gain is 11 dB. THD plus noise measures 0.002%, noise is specified at -110 dBV, and crosstalk is 68 dB. The frequency response runs from 20 Hz to 80 kHz within plus or minus 0.02 dB. Output impedance stays below 1 ohm. The case measures 103 x 37 x 120 mm and the unit weighs 365 g without its power supply. Standby consumption is under 0.1 W.

Engineering and use context

Connectivity is kept simple. One RCA input pair takes the line signal, and two headphone sockets are provided, one 6.3 mm jack and one 3.5 mm jack. Both headphone outputs may be driven simultaneously, which allows two people to listen to the same source together. The bypass RCA loop output sends the incoming line signal on to a further amplifier, which lets the Head Box S2 be inserted ahead of the main amplifier without taking an input away from it. The circuit uses low noise components, and the case uses layered aluminium and metal walls meant to shield the electronics from vibration and electromagnetic interference. Power comes from an external 5 V 0.5 A DC supply. Pro-Ject offers the Accu Box S2 and Accu Box S2 USB battery power supplies as compatible upgrades, which replace the standard adapter. The sub-1-ohm output impedance keeps the output stage from loading down the headphone driver, and the moderate gain gives headroom for low sensitivity models.

Pairing

As a line level device without its own converter, the Head Box S2 needs a line level source like a CD transport with DAC, a DAC or a phono stage with RCA outputs. Within the same S2 size family, Pro-Ject's DAC and phono preamplifier boxes share the small chassis width, so a stack of matching units can be built on a desk or shelf. The loop output allows a power amplifier or active speakers to stay connected to the same source.

Alternatives

The Pro-Ject Head Box S2 Digital is a headphone amplifier of the same size class that adds a built-in DAC for digital sources.