Pro-Ject Head Box S2 Digital Headphone Amplifier and DAC - Black

A Headphone Stage Worth the Name

Most amplifiers treat the headphone socket as an afterthought, tapped off the speaker output through a resistor. The Pro-Ject Head Box S2 Digital exists to replace that, and to add a headphone output to gear that never had one at all.

It is a converter and a headphone amplifier in a small aluminum case. The quarter-inch jack sits on the front, and every part behind it was chosen to feed that jack rather than to fill out a specification sheet.

What It Decodes

Over USB it handles PCM up to 32-bit and 768kHz, and DSD up to quad rate, DSD256. The optical and coaxial inputs take up to 24-bit and 192kHz, which covers a television or a disc transport comfortably.

Five Filters, and Quiet Power

Five digital filters are selectable, including Pro-Ject's own Optimum transient filter. They change the character of the sound in small ways, which is the point: a way to adjust without touching anything else in the chain.

The USB Noise Problem, Handled

Noise arriving over USB is filtered twice before it reaches the audio circuit. That is the single biggest weakness of computer-fed audio, and it is where a box like this earns its place over a socket on the back of a laptop.

Three digital inputs mean a computer, a television and a transport can all stay connected. The case is aluminum, the parts were picked rather than specified down to a price, and the whole thing takes up almost no desk.

Who Is This Headphone Amp Best For?

• Your amplifier's headphone socket disappoints — this replaces it with a stage built for the job, which is the cheapest real upgrade most systems have available.
• Your amplifier has no headphone socket at all — plenty of good ones do not, and this adds the capability without changing anything else.
• You feed it from a computer — USB noise is filtered twice on the way in, which is the difference between a laptop socket and a proper chain.
• You like to adjust by ear — five selectable filters, including Pro-Ject's Optimum transient design, change the character without an app or a menu.
• Every input on it is digital — a turntable or a tuner has no way in, so an analog source needs its own path to your system. See our integrated amplifiers for that side.

How Does It Connect to Your System?

A computer connects on USB-B, a television on optical, and a disc transport on coaxial. All three can stay plugged in, and the front panel switches between them.

Headphones use the quarter-inch jack on the front. USB carries the highest rates, up to 32-bit and 768kHz with DSD256, while optical and coaxial run to 24-bit and 192kHz.

Pairs Well With

Building your system? Here are some great companions:

• Headphones: The reason this box exists — see our Headphones.
• Headphone Cables: To get the best from a good pair — browse our Headphone Cables.
• DAC: If the system grows past this — see our DACs.
• Integrated Amplifier: For the speaker side of the system — see our Integrated Amplifiers.

Frequently Asked Questions

What resolution does it handle?

Up to 32-bit and 768kHz PCM with DSD256 over USB. The optical and coaxial inputs take up to 24-bit and 192kHz.

How many sources can I connect?

Three at once: USB-B for a computer, optical for a television, and coaxial for a transport.

What do the filters do?

Five are selectable, including Pro-Ject's Optimum transient filter. Each changes the character of the sound slightly.

Can I connect a turntable?

Every input is digital, so a turntable needs a phono stage and a separate path into your system.

Why does USB noise matter?

Computers are electrically noisy. The Head Box S2 Digital filters that noise twice before it reaches the audio circuit.

What is the case made of?

Aluminum and metal throughout, in the compact Box-series format.

See It in Action

Pro-Ject walks through the Head Box S2 Digital:

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Learn More

Want to learn more about headphone amplifiers, DACs, or building a desktop system? Visit our Learning Center for guides, tips, and expert advice.