Pre Box S2 Digital – Edition 23

Digital micro preamplifier with MQA and DSD512 support

Improved 2023 edition of a Modern Pro-Ject Classic

The Pre Box S2 Digital – since its release back in 2017 – has quickly ascended to an exceptional status in the DAC market and gained a reputation among digital and PC-audio enthusiasts for its remarkable ability to compete way above its price point.

This achievement can be attributed to a combination of factors, including a custom and proprietary clock design, meticulous PCB layout featuring separate power supplies, dual differential ESS DACs, and an exclusive proprietary digital filter designed to deliver pristine and transparent transient response. The Pre Box S2 Digital may seem small, but it is really the ultimate design.

The chip crisis of 20/21 has hit the Pre Box S2 Digital particularly hard, given its enduring demand. But during the downtime, we and original designer John Westlake seized the opportunity to implement key improvements and refine the design, thus rejuvenating the product almost exactly 5 years after its original introduction.

Edition 23 Improvements

New internal power supply design

The power supply units (PSUs) of clock, DACs, and analog output stages have undergone enhancements to offer increased isolation from PC USB power noise and achieve a wider/flatter output impedance across the entire audio bandwidth.

Redesigned master audio clocks

We have redesigned and improved the discrete audio master clocks – this lowers the phase noise and further,enhances the already cutting-edge jitter performance.

New output stage with higher Class-A current

The new analogue output stage, based around the SABRE9603Q, has higher Class A operating current, for improved performance with low impedance headphones and long cable runs.

New headphone amplifier

The entire design is now more energy efficient – a 12% reduction in PSU current, while also offering higher Class A analogue stage operating current resulting in lower distortion when used with low impedance headphones. Users with mobile devices or laptops on-the-go will also appreciate the lower power draw, and simultaneously enjoy more power for the energy that is being drawn. And for anyone finding themselves using low-impedance headphones or in-ears – whether in a mobile, home, or work environment: they will experience a noteable boost in sound quality too.

Unbeatable value – handmade in Europe

Normally up to 70% of Hi-Fi production cost goes into the cabinet. By reducing the cabinet size and using the same casework for entire product-lines Pro-Ject can shift the cost-relation to the benefit of technology involved. This allows us to invest in a higher quality PCB design. The Pre Box S2 Digital Edition 2023 is carefully designed and handmade in Europe. We aim to develop a technically flawless device in a housing that is only as big as necessary to save raw materials. Due to the timeless design & rigid aluminium casework, the Pre Box S2 Digital Edition 2023 is built for eternity.

Available in:


  • Edition 23: powerful output stage for headphones
  • Edition 23: analogue output stage - higher Class A current
  • Edition 23: redesigned discrete audio master clock
  • Edition 23: internal power supply design
  • Edition 23: less energy consumption - more power, higher efficiency - saves battery life for mobile devices
  • Edition 23: Jitter even lower than 100 Femtoseconds!
  • Dual mono high end ESS Sabre ESS9038 dual DAC
  • Organic polymer capacitors and thin film miniMELF resistors
  • MQA hardware decoding
  • DSD64, DSD128, DSD256 & DSD512 (DoP, DSD512 native)
  • Up to 24bit/192kHz for optical & coax inputs
  • 8 selectable digital filter characteristics
  • 1 proprietary optimum transient digital filter
  • Headphone output on the front (6.3mm)
  • Synchronization of all internal oscillators
  • Gold plated four layer PCB
  • Full alu/metal sandwich casing in silver or black


It is clearly labelled on the packaging. Another way is to go by Serial Number. All units where the Serial Number is starting with 22 and higher have the Edition 23 improvements.

The device is fully compatible with Windows 10. It may be necessary to reinstall latest drivers after updating from Windows 7/8/8.1 to Windows 10.

You do not need a driver. The driver is already integrated in the operating system.

Turn off your Computer and press at start alt+cmd+p+r until another starting sound appears. With this command the USB bus will be reset and the USB Box will be recognized new.

Pre Box S2 Digital will show the MQA logo and a blue dot on the display's top right corner once an MQA file has been successfully passed on to it.

No, in order to enable MQA playback via S/PDIF a hardware change would be necessary, this would cause the price to go much higher. MQA hardware decoding is only possible via the asynchronuous USB input of Pre Box S2 Digital.

The DFU for MacOS requires the Pre Box S2 Digital to run software version 2.10. (July 2018)

It can occur that the sound gets distorted using these highest sample rates. After about three minutes the filter "locks" in properly and the sound should be normal again. Also switching sample rates back and forth can help to make it sound normal again. Unfortunately that's a bug in the ESS silicone chip and we can't do anything about it.