Disc Players

For a pair of ostensibly simple-looking small boxes, this Pro-Ject duo packs-in a couple of days' worth of lab test features! The two pairs of 6922EH triodes that form the tube output option, for example, are an addition to the solid-stage output. Distortion and noise are slightly increased [see Graph 1, below], though this is an increase in 2nd-order harmonic from 0.0055% to 0.008% only (1kHz/0dBFs) while the A-wtd S/N falls slightly from a very respectable 113dB to a still very fine 110dB in tube mode. The maximum 4.1V balanced output is unaffected by choice of solid-state/tube stage but the output impedance does increase from 173ohm to 320ohm (the latter increasing still further to 1.74kohm at 20Hz), respectively.

There is no impact on the Pre Box RS2's digital performance, of course, which is influenced to a greater degree by your choice of digital filter. Using the default 'Linear Phase Fast' filter, the response reaches out to –0.1dB/20kHz, –0.9dB/45kHz and –2.1dB/90kHz with CD/48kHz, 96kHz and 192kHz media, respectively, with –0.14dB/20kHz, –0.6dB/45kHz and –1.8dB/90kHz achieved via the 'Minimum Phase Fast' filter. Distortion falls to as low as 0.00015% over the top 30dB of its dynamic range through bass/midrange frequencies and 0.0006% at 20kHz. There are synchronous clocks for 44.1kHz and 48kHz-based digital sources, offering an accuracy of ±20ppm, while jitter, via the clock-linked HDMI/I2S interface falls to 220psec [see black spectrum, Graph 2]. There is more low-level spuriae present via the S/PDIF and USB inputs with 24-bit data [red spectrum, Graph 2] but correlated jitter is lower at 160psec. Low-level linearity is good to ±0.1dB over a 100dB range. PM