Pro-Ject Pre Box RS2 Digital – High-end preamplifier with DAC and headphone amplifier

As the big brother of the Pro-Ject Pre Box S2 Digital, Pro-Ject Audio Systems refers to the Pro-Ject Pre Box RS2 Digital, which, as the name suggests, comes from the Pro-Ject Box Design RS2 Series and combines the tasks of a preamp with an integrated D/A converter and is also equipped with an integrated headphone amplifier.

With the Pro-Ject Pre Box S2 Digital, Pro-Ject Audio Systems delivered a true masterpiece. This solution is distinguished first and foremost by its immense versatility. It is an outstanding D/A converter operating at the highest level, combined with a preamplifier and headphone amplifier. Pro-Ject Audio Systems rightly speaks of a groundbreaking solution that has been used as the basis for a solution that is a few classes higher, namely the Pro-Ject Pre Box RS2 Digital.

Even though the Pro-Ject Pre Box S2 Digital is part of the Pro-Ject Box Design S2 Series, it can still be described as the little brother of the Pro-Ject Pre Box RS2 Digital from the reference series Pro-Ject Box Design RS2 Series, because not only the concept is the same, but also the D/A converter, which is an essential feature of the new Pro-Ject Pre Box RS2 Digital. Of course, the Pro-Ject Pre Box RS2 Digital’s range of functions has been expanded and the sound potential has been pushed to new heights, so that it is an immensely versatile preamplifier that works either in solid state or tube, offers both digital and analogue source connections, and also has an excellent headphone amplifier.

As just mentioned, the Pro-Ject Pre Box RS2 digital converters of the type ESS Sabre ESS9038Q2M DAC are also used in the Pro-Ject Pre Box RS2, whereby two of these integrated circuits are used to achieve a completely separate signal path for the left and right channels. The signal processing here allows data in Linear PCM with up to 23 bit and 768 kHz and DSD with up to DSD512. Of course, signals encoded in MQA can also be processed, although the manufacturer emphasizes that this is a complete hardware and software support. This also applies to upsampling, which the Pro-Ject Pre Box RS2 Digital offers, with eight filters available for signal processing. One of them is even intended for MQA, namely the proprietary Optimal Transient Digital Filter.

Although the Pro-Ject Pre Box RS2 Digital offers a wide range of digital interfaces, the most flexible of these is of course a USB 2.0 port for direct connection to a PC, Mac, but also a streaming client such as the Pro-Ject Stream Box S2 Ultra. Signal processing is performed by a powerful multi-core XMOS microcontroller with advanced multi-core RISC architecture. For re-clocking, the CPLD MAX II (Complex Programmable Logic Device) from Altera is used, which, together with the XMOS controller, guarantees particularly high-quality processing. By the way, we want to emphasize that the solution is called Roon Tested DAC, which means that it can be accessed directly via the software on a PC or Mac.

Another very important interface on the digital level of the Pro-Ject Pre Box RS2 Digital is an HDMI port, which, however, is only intended for audio signals, directly as I2S, so that, for example, the Pro-Ject CD-Box RS2 T CD-Transport can be connected here, whereby the master clock with 16.9344 MHz of the Pro-Ject Pre Box RS2 Digital then literally sets the pace.

In addition, there are two optical and one coaxial S/PDIF interface that can transmit signals in Linear PCM at up to 24 bits and 192 kHz. An AES/EBU is also available, which also transmits signals in Linear PCM at up to 24 bits and 192 kHz.

Those who want to use smartphones, tablets or portable audio players as a source can do so with the Pro-Ject Pre Box RS2 Digital via the integrated Bluetooth module, which corresponds to Bluetooth 4.0 and supports aptX in addition to SBC and AAC.

When it comes to analog signals, the Pro-Ject Pre Box RS2 Digital can be connected either via a pair of RCA sockets or a pair of XLR connectors. This may not seem like a lot, but in times of “digital” sources this is sufficient, for example for the integration of a record player.

The analogue section of the Pro-Ject Pre Box RS2 Digital, which is also fully balanced in a dual-mono design, has a special feature that we have already mentioned briefly. You have the choice of relying on solid state, i.e. transistor, or tubes. Four glass bulbs of the type 6922EH are available here on request.

The output section of the Pro-Ject Pre Box RS2 Digital is equipped with unbalanced Cinch connectors, but of course also balanced XLR sockets.

The manufacturer especially emphasizes the headphone amplifier of the Pro-Ject Pre Box RS2 Digital, which, according to Pro-Ject Audio Systems, does not require any compromises and thus even high-quality headphone models can be controlled without any problems. For example, there is no need for coupling capacitors at all, even at the output. The entire amplifier is DC-coupled. A very fast DC servo is used to ensure that there is no DC voltage at the output. The output power is suitable for all kinds of headphones. Headphones are connected here via a 6.3 mm stereo jack socket.

For the sake of completeness, it should be mentioned at this point that the Pro-Ject Pre Box RS2 Digital naturally provides trigger inputs and outputs, so that it is possible to control additional components.

The front of the Pro-Ject Pre Box RS2 Digital features a generously dimensioned display that clearly shows all parameters. Of course, the user will find all relevant controls directly on the front, especially a rotary encoder for volume control.

From a distance, the Pro-Ject Pre Box RS2 Digital can be controlled via an infrared remote control. This is a high-quality model made of aluminium.

The housing of the Pro-Ject Pre Box RS2 Digital itself is also made of aluminium in the proven manner, whereby the customer has the choice of either silver or black.

The Pro-Ject Pre Box RS2 Digital measures 206 mm in width, 222 mm in depth and 72 mm in height. This brings 1,710 g to the scales.

Power is supplied by an external power supply unit, which is naturally included in the scope of delivery. Optionally, the power supply can be upgraded using the Pro-Ject Power Box RS Uni 1-way or Pro-Ject Power Box Uni 4-way.

Getting to the point

Even though the Pro-Ject Pre Box S2 Digital originates from the Pro-Ject Box Design S2 Series, it can still be called the little brother of the Pro-Ject Pre Box RS2 Digital from the reference series Pro-Ject Box Design RS2 Series, because not only the concept is similar, but also the D/A converter, which is a very important feature of the new Pro-Ject Pre Box RS2 Digital. Of course, the Pro-Ject Pre Box RS2 Digital’s range of functions has been expanded and the sound potential has been pushed to new heights, so that it is an immensely versatile preamplifier that works either in solid state or tube, offers both digital and analogue source connections, and also has an excellent headphone amplifier.