Предусилители — Pro-Ject Pre Box RS2 Digital

The Pre Box RS2 Digital from Pro-Ject Audio Systems combines a line preamplifier, a DAC and a headphone amplifier in one box, and Pro-Ject presents it as the larger sibling of its Pre Box S2 Digital. It uses a fully balanced dual-mono layout with an output buffer that can be switched between solid-state and tube operation, and buyers can choose a silver or black case. The list price was EUR 2,199.

Key specs that matter

Two ESS9038Q2M converters, one for each channel, do the decoding, accepting PCM up to 32 bit and 768 kHz plus DSD up to DSD512 over USB, both as DoP and native. Digital inputs include USB 2.0, I2S, a coaxial and a pair of Toslink S/PDIF ports (24/192), a balanced AES/EBU input (24/192) and Bluetooth 4.0 supporting SBC, AAC and aptX codecs. Analogue sources connect via balanced XLR or single-ended RCA, each with 15 kOhm input impedance. Pre-outs are on XLR and RCA, and their source impedance is 180 ohms in solid-state mode and 220 ohms with tubes. THD+N from 20 Hz to 20 kHz is below 0.006% solid-state and 0.017% via tubes, measured at 2 V RMS and 1 kHz. The 6.35 mm headphone jack gives 90 mW into 300 ohms, 245 mW into 32 ohms and 150 mW into 8 ohms.

Engineering and use context

The tube buffer uses four 6922EH valves. Re-clocking relies on an XMOS multi-core processor with RISC architecture and an Altera MAX II CPLD. Eight digital filters are selectable, including a proprietary MQA transient filter, and MQA files are fully unfolded in hardware. A 16.9344 MHz master clock output and the I2S link are intended for the CD Box RS2 T transport. A display sits on the front, and an aluminium remote is supplied. Besides MQA, the unit is certified for DSD and Hi-Res Audio and works with Audirvana. It draws power from a 20 V, 3 A DC supply working on 110 to 240 V mains, uses at most 1.2 A DC and less than 0.5 W in standby. The case is 206 x 72 x 222 mm with sockets and weighs 1710 g without the supply. It is Roon Tested.

Pairing

The balanced pre-outs feed a power amplifier such as the Amp Box RS2 from the same series, and the CD Box RS2 T can be clocked from this preamp for disc playback. Headphone listeners can plug directly into the front socket without a separate headphone amplifier, and a phone or tablet can stream over Bluetooth while a computer uses the USB port.

Alternatives

Pro-Ject's Pre Box S2 Digital offers a smaller preamplifier and DAC in the same Box Design family.