Pioneer DV-AX10 SACD/DVD-A/CD player Measurements

Sidebar 3: Measurements

I measured the Pioneer from its main L and R outputs, mostly from the balanced XLR jacks, with some repeated measurements from the unbalanced RCAs. The output was non-inverting from both sets of jacks, the XLRs apparently wired with pin 2 "hot." The source impedance was a moderate 455 ohms from the RCAs across most of the audioband, this rising inconsequentially to 477 ohms at 20Hz. As usual, the balanced output impedance was exactly twice that of the unbalanced. The maximum unbalanced output level from CD and DVD was 2.3V, 1.2dB above the CD Standard's 2V RMS. However, the maximum level from SACD was 2.5dB lower: 1.69V. Unless compensated for in side-by-side comparisons, this very audible difference will work to the disadvantage of the hi-rez medium, making it sound less dynamic.

Error correction, tested with the Pierre Verany Test CD, was very good, the player coping with gaps in the CD's data spiral up to 1.25mm in length without audible dropouts or glitches.

Channel separation (not shown) was superb at better than 120dB below 8kHz, and still an excellent 112dB at 20kHz. The player's frequency response with and without pre-emphasis from CD (fig.1) was essentially flat. I must admit that this surprised me a little, as the DV-AX10 uses Pioneer's Legato Link digital filter. My earlier experience of this filter had suggested it is conceptually similar to Wadia's DigiMaster in that it trades off a slower-than-usual stop-band rejection in favor of improved time-domain performance. The usual result of such a filter is an audioband response down 3dB at 20kHz.

Fig.1 Pioneer DV-AX10, balanced CD frequency response at -12dBFS, without emphasis (top) and with emphasis (bottom). (Right channel dashed, 0.5dB/vertical div.)

Using the "provisional" Sony Test SACD, the Pioneer's ultrasonic response (fig.2) rolled off considerably earlier than with other SACD players I have measured, the output being 3dB down at 40kHz, with then a brickwall filter apparent. This would seem to negate some of the claimed sonic advantages for SACD, which can preserve recorded audio information up to 100kHz.

Fig.2 Pioneer DV-AX10, SACD frequency response at -3dBFS (right channel dashed, 0.5dB/vertical div.).

I don't have a test DVD with an ultrasonic frequency sweep on it, and so was unable to test the DV-AX10's supra-audio output with wideband material. However, the Chesky Test DVD (CHDVD171) does have a 96kHz-sampled 12kHz squarewave on it. Because the third harmonic of the 12kHz fundamental lies at 36kHz, below the medium's nominal 48kHz cutoff, it should reproduce with more of a square shape than with CD's 44.1kHz sampling. Fig.3 shows that this is indeed the case. However, the result is a little too square, which either means the Legato Link filter is adding information above the nominal passband or, more likely, is clipping the peaks of this full-scale waveform, presumably to maximize low-level performance. Repeating the test with 48kHz sampling gives the result shown in fig.4: what should be a straightforward sinewave, due to the absence of any of the odd harmonics that lie above the 24kHz passband, is squared-off.

Fig.3 Pioneer DV-AX10, 12kHz squarewave, 96kHz LPCM data.

Fig.4 Pioneer DV-AX10, 12kHz squarewave, 48kHz LPCM data.

I examine the ultimate resolution of hi-rez players by comparing the spectrum of a dithered low-level 1kHz tone played back from CD (where the noise floor these days will be mainly due to the recorded dither) with that of an identical tone played back from 24-bit DVD or an SACD. Fig.5 shows such spectral analyses performed on the DV-AX10's output while it decoded CD data (top traces) and SACD data (bottom traces). The signal from the DSD-encoded disc has a noise floor at least 12dB lower than CD over most of the band, suggesting a resolution of at least 18 bits, which is excellent. There is, however, a peculiar "bump" at 5kHz in the CD traces. Note also that the top-octave rise in the SACD's noise floor starts higher in frequency compared with the Sony and Philips players we have reviewed, presumably due to the more aggressive low-pass filtering employed by the Pioneer for SACD playback.

Fig.5 Pioneer DV-AX10, 1/3-octave spectrum of dithered 1kHz tone at -90dBFS, with noise and spuriae (from top to bottom): 16-bit CD data, DSD SACD data (right channel dashed).

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