The Pro-Ject Pre Box S2 Digital is Pro-Ject Audio Systems' flagship compact desktop DAC and headphone amplifier, sitting at the pinnacle of their S-series HiFi electronics range. Since its original release in 2017, it earned an exceptional reputation among digital audio and PC-audio enthusiasts for its ability to compete well above its price point. The 2023 Edition, also known as Edition 23, represents a comprehensive refinement of the original design, implemented by Pro-Ject and original designer John Westlake during a period of enforced downtime caused by the global chip shortage of 2020-2021.
Dual ESS Sabre DAC Technology
At the heart of the Pre Box S2 Digital is a dual mono configuration featuring two ESS9038Q2M 32-bit DAC chips running in parallel, one per channel. This dual mono layout, combined with Pro-Ject's proprietary clock design and a gold-plated four-layer PCB, delivers exceptional channel separation and an exceptionally low noise floor. The device supports PCM playback up to 32-bit/768kHz via USB, and up to 24-bit/192kHz via its optical and coaxial inputs. DSD support is comprehensive, covering DSD64, DSD128, DSD256, and DSD512 in both DoP and native formats. Full MQA hardware decoding is also included, allowing the unit to unfold MQA files from services such as TIDAL. Eight selectable digital filter characteristics plus a proprietary optimum transient filter give users precise control over the digital reproduction character.
Connectivity and Outputs
The rear panel provides three digital inputs: a USB Type-B socket accepting signals up to DSD512 and 32-bit/768kHz PCM, a coaxial S/PDIF input on RCA, and an optical TosLink input, both supporting up to 24-bit/192kHz. Output is via a pair of variable RCA line outputs and a front-mounted 6.3mm headphone socket rated down to 8 ohms minimum impedance, delivering 100mW into 32 ohms and 6.6mW into 600 ohms. Volume control is handled by the front-panel rotary knob, with a full-function remote control included. The unit is supplied with a 5V/1A DC outboard power supply.
Edition 23 Improvements
The 2023 Edition introduces a series of targeted hardware upgrades over the original. The power supply units for the clock, DAC chips, and analogue output stages have been redesigned to provide greater isolation from USB noise and to achieve a wider, flatter output impedance across the full audio bandwidth. The discrete audio master clocks have been redesigned to lower phase noise and push jitter performance below 100 femtoseconds. The analogue output stage, now based around the ESS SABRE9603Q, runs at higher Class A operating current, improving performance into low-impedance headphones and over long cable runs. Overall power consumption has been reduced by 12 per cent while simultaneously delivering more output power, which is particularly beneficial for users running the unit from a laptop USB port on the move. The unit is available in silver or black, with a full aluminium sandwich casing and timeless industrial styling handmade in Europe.
