Disc Players

Although the PM-KI Ruby uses the same Ncore NC500 Class D amp module found in the PM-10 [HFN Aug '17] its single-ended implementation here yields subtle differences in performance. Once again, Marantz's power specification proves to be very conservative as its 100/200W 8/4ohm rating is bested to the tune of 170W/280W in practice, with 200W, 360W, 610W and 370W achieved under dynamic conditions into 8, 4, 2 and 1ohm loads [see Graph 1, below]. So while the PM-KI Ruby's 8/4ohm output is only a third that of the PM-10, its ability to drive very low impedance speakers is actually superior. On the other hand, without bridged operation, distortion is slightly higher – especially at high frequencies (0.03% vs. 0.12% at 20kHz/0dBW) – and the A-wtd S/N rather poorer at 80dB vs. 91dB (both re. 0dBW). Once again, however, the response remains unaffected by loading and is almost identical to that of the PM-10, reaching out to –0.6dB/20kHz and –6.3dB/100kHz.

Marantz's partnering SA-KI Ruby player offers a 1.99V analogue output with a modest 102dB A-wtd S/N ratio and distortion that's just 0.0002-0.00025% (20Hz-20kHz) with Filter 1 [see Graph 2] and fractionally higher at 0.0005% with Filter 2. The response (and stopband rejection) depends on your choice of digital filter: 'Filter 1' is a slow roll-off type with minimal pre/post ringing that offers a mere 4.1dB image rejection and a roll-off of –4.9dB and –3.8dB/20kHz (CD/48kHz files), –7.6dB/45kHz (96kHz files) and –21dB/90kHz (192kHz files). 'Filter 2' has more post-event ringing with a slightly 'flatter' –1.5dB/20kHz, –5.2dB/45kHz and –15dB/90kHz response. Jitter is low with 24-bit LPCM sources at 65psec and just 25psec with SACD. PM