Pro-Ject Pre Box RS2 Digital
Dual-mono preamplifier DAC with ESS9038Q2M chips, hybrid valve/transistor output and built-in headphone amplifier, for high-end hi-fi systems.
Description
The Pre Box RS2 Digital is a digital-to-analogue converter combined with a preamplifier and headphone amplifier, designed to serve as a central digital source in a high-end hi-fi chain. It processes digital streams from a computer or transport and outputs an analogue signal that can be fed directly to a power amplifier or active speakers.
Its conversion relies on two ESS9038Q2M chips mounted in dual mono configuration, with separate signal paths for the left and right channels, an arrangement that limits interference between channels and improves stereo separation. These converters accept files up to 32-bit/768 kHz in PCM and up to DSD512, and the unit includes full hardware and software support for the MQA format. Eight digital filters, including an optimal transient filter, allow the sound to be adjusted according to listening preferences. USB stream processing is handled by a multi-core XMOS microcontroller paired with an Altera MAX II CPLD for clock resampling. The analogue output combines a transistor stage and a valve stage, user-selectable, with an output impedance of 180 ohms in solid-state mode and 220 ohms in valve mode; the input impedance is 15 kΩ. Preamp outputs are available in XLR and RCA. The headphone amplifier, on a 6.35 mm jack socket, is fully DC-coupled, with no coupling capacitor even at the output, with a DC servo ensuring the absence of residual DC voltage.
- Dual-mono ESS9038Q2M DAC, 32-bit/768 kHz, DSD512
- Eight digital filters and full MQA compatibility
- Selectable hybrid valve/transistor output
- XLR and RCA preamp outputs, 6.35 mm jack headphone output
- Standby consumption below 0.5 W
This preamplifier DAC is aimed at hi-fi enthusiasts wishing to pair a high-performance digital source with a power amplifier or high-end active speakers, as well as demanding headphone listening thanks to its dedicated no-compromise stage. Its filtering versatility and the choice between valve or transistor output make it an instrument suited to those wishing to precisely fine-tune the sonic character of their system.
Technical specifications
| DAC | 2x ESS9038Q2M (dual mono - 32-bit/768 kHz/DSD512) |
| Input impedance | 15 kΩ |
| Output impedance | 180 ohms solid-state, 220 ohms valve |
| Analogue outputs | Preamp output (XLR and RCA), headphone (6.35 mm jack socket) |
| Power consumption | Max. DC current: 1.2 A, standby consumption: < 0.5 W |
What to check before buying used
The valves in the hybrid output stage are wear items to watch out for: hum, loss of gain or one channel weaker than the other may indicate a tired valve in need of replacement. Check that both output modes, valve and transistor, work correctly, as well as the switching between them. Also check that the XLR, RCA and headphone jack outputs deliver a clean signal on both channels, without crackling or dropouts.
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