DACs — Pro-Ject DAC Box RS Final Edition

The DAC Box RS Final Edition is a reference-class digital to analogue converter from Pro-Ject Audio Systems, issued as a send-off for the classic DAC Box RS with exclusive modifications. It is meant for digital stereo sources and also works as a USB audio interface for high-resolution computer playback. Pro-Ject fits selected Diamond ECC88 tubes, which it values at EUR 199 each, and selected electrical components with improved internal wiring, and buyers can order the metal casing in silver as well as black.

Key specs that matter

Conversion uses two Texas Instruments PCM-1792 chips in an 8x oversampling design. Supported sample rates are 32, 44.1, 48, 88.2, 96, 176.2 and 192 kHz, with the optical input limited to 96 kHz. Asynchronous USB based on XMOS technology accepts 24 bit and 192 kHz, and DSD up to DSD128 is handled as DSD over PCM. Frequency response is 20 Hz to 50 kHz within plus 0 and minus 1 dB, with a 100 dB signal to noise figure. Distortion is 0.005% from the solid-state output and 0.25% from the tube output. Maximum output voltage is 4 V on XLR and 2 V on RCA at 1 kHz. The case measures 206 x 72 x 210 mm including the sockets, and the unit weighs 1890 g without its supply.

Engineering and use context

Pro-Ject lists nine input options covering USB, AES-EBU, optical Toslink and coaxial S/PDIF. An I2S interface is included along with a BNC port for clock synchronisation. Two digital filter settings, named steep and optimum phase, can be selected. The output stage can be switched between the tube circuit and a solid-state Class A circuit, and the maker describes the design as ultra linear with ultra low noise circuitry. Power comes from an outboard 20 V, 3 A DC supply, and standby consumption stays below 1 watt. Maximum current draw is 800 mA in tube mode and 300 mA in solid-state mode. An infrared remote control is supplied.

Pairing

Pro-Ject names no partner amplifier for the Final Edition. Line outputs come in both balanced XLR and unbalanced RCA form, so the converter connects to either kind of input on an amplifier or preamp. A disc transport or network player with a digital output can feed the unit, and a computer is linked through the USB port.

Alternatives

Pro-Ject's DAC Box RS2 is another converter in the Box series, built around two ESS9038Q2M chips in dual mono with a 6922 tube or solid-state output, PCM to 32 bit and 768 kHz, DSD512 and full hardware MQA unfolding, six digital inputs including I2S over HDMI and an output impedance of 180 ohm in solid-state mode.