A Transport of Delight: CD Transport Jitter Page 6

Figs.15 and 16 show the Meridian 200 transport's jitter on test signals and music, respectively. The -90dB, 1kHz test signal (the trace with the highest peak at 1kHz) produced a fairly high—but typical—jitter level at 1kHz and 2kHz.

Fig.15 Meridian 200, jitter in S/PDIF data signal, 20Hz-50kHz, when transmitting digital silence (solid), a 1kHz sinewave at -90dB (dashed), and a 1kHz sinewave at 0dBFS (dotted) (vertical scale, 1ps-2ns, 100µV = 1ps).

Fig.16 Meridian 200, jitter in S/PDIF data signal, 20Hz-50kHz, when transmitting music #1 (solid) and music #2 (dashed) (vertical scale, 1ps-2ns, 100µV = 1ps).

Figs.17 and 18 show the JVC XLZ-1010's jitter. Note the much more pronounced jitter signature, seen as the characteristic shape of the curves. We see jitter energy concentrated at 540Hz, with additional peaks at 180Hz, 360Hz, and 1.8kHz (frequencies that are all harmonically related). The overall RMS level is moderately high, measuring a low of 71ps and a high of 201ps.

Fig.17 JVC XLZ-1010, jitter in S/PDIF data signal, 20Hz-50kHz, when transmitting digital silence (solid), a 1kHz sinewave at -90dB (dashed), and a 1kHz sinewave at 0dBFS (dotted) (vertical scale, 1ps-2ns, 100µV = 1ps).

Fig.18 JVC XLZ-1010, jitter in S/PDIF data signal, 20Hz-50kHz, when transmitting music #1 (solid) and music #2 (dashed) (vertical scale, 1ps-2ns, 100µV = 1ps).

The Mark Levinson No.31's jitter is shown in figs.19 and 20. The spectrum is much smoother—indicating fewer periodic jitter components—than the JVC, and the overall RMS level is lower. Still, with the vertical scaling adopted for these graphs, the No.31 wasn't obviously better than the other transports, despite its generally acknowledged superior sound quality.

Fig.19 Mark Levinson No.31, jitter in S/PDIF data signal, 20Hz-50kHz, when transmitting digital silence (solid), a 1kHz sinewave at -90dB (dashed), and a 1kHz sinewave at 0dBFS (dotted) (vertical scale, 1ps-2ns, 100µV = 1ps).

Fig.20 Mark Levinson No.31, jitter in S/PDIF data signal, 20Hz-50kHz, when transmitting music #1 (solid) and music #2 (dashed) (vertical scale, 1ps-2ns, 100µV = 1ps).

The C.E.C. TL 1 had a very similar spectrum and RMS jitter compared to the No.31, as shown in figs.21 and 22. The C.E.C.'s 2kHz jitter peak, produced when transmitting a -90dB, 1kHz sinewave, was lower in amplitude than that of the No.31, and the subcode peaks at 7.35kHz and 14.7kHz are also lower. Further, the No.31 had more jitter energy at 2kHz and 3kHz when transmitting a full-scale, 1kHz sinewave (middle traces in figs.19 and 21). However, the C.E.C. has more spikes in the jitter energy below 200Hz compared to the No.31. We'll take a closer look at these differences later.

Fig.21 C.E.C. TL 1, jitter in S/PDIF data signal, 20Hz-50kHz, when transmitting digital silence (solid), a 1kHz sinewave at -90dB (dashed), and a 1kHz sinewave at 0dBFS (dotted) (vertical scale, 1ps-2ns, 100µV = 1ps).

Fig.22 C.E.C. TL 1, jitter in S/PDIF data signal, 20Hz-50kHz, when transmitting music #1 (solid) and music #2 (dashed) (vertical scale, 1ps-2ns, 100µV = 1ps).

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COMMENTS
p_f_m's picture

Hi, first of all thank you very much for doing this. It is very informative and I appreciate your time and efforts you spent on this. I do have a couple of questions though -

For the audibility tests, did you test the players/sources using the same outboard dac via spdif ? or were you listening to the analog outputs of the playback sources ?

Comparing the worst v/s the best is a great way of highlighting the differences and to educate users how jitter sounds like, however I feel it would have been perfect, especially after having spent the time and effort to come this far anyway, if you could have also thrown in to the listening test one or two players that had "average" or not too bad or good jitter. This would have kind of helped understand approximately whereabouts might be the threshold of audibility of jitter.

Thank you! and looking forward to hearing from you.

-PFM.

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