A Transport of Delight: CD Transport Jitter Page 7

Although I haven't yet auditioned it, I measured the gorgeous new $8000 Denon DP-X transport (figs.23 and 24). The DP-X had very low jitter below 200Hz, but slightly higher jitter in the treble. The 2kHz component in the top trace (made with the -90dB, 1kHz test signal) is lower in amplitude than any of the other products tested, but it had more jitter energy above 3kHz when the transport was transmitting a full-scale, 1kHz sinewave. The DP-X had a slightly higher jitter level on music than the best of the transports tested.

Fig.23 Denon DP-X, 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.24 Denon DP-X, jitter in S/PDIF data signal, 20Hz-50kHz, when transmitting music #1 (solid) and music #2 (dashed) (vertical scale, 1ps-2ns, 100µV = 1ps).

The Pioneer CD-65, seen in figs.25 and 26, had higher jitter than the best transports, but lower jitter than the JVC XLZ-1010. We can see a jitter spike at 60Hz, no doubt due to power-supply noise. What is the subjective effect of jitter energy concentrated at 60Hz? We don't yet know.

Fig.25 Pioneer CD-65, 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.26 Pioneer CD-65, jitter in S/PDIF data signal, 20Hz-50kHz, when transmitting music #1 (solid) and music #2 (dashed) (vertical scale, 1ps-2ns, 100µV = 1ps).

The most surprising performance was from the $695 California Audio Labs Delta transport (figs.27 and 28). The Delta had low RMS jitter (50ps average for the five signals) and a fairly clean spectrum. However, we can see jitter energy at the power-line frequency of 60Hz in all three traces. Interestingly, the Delta showed very little change in jitter level between the two musical selections.

Fig.27 CAL Delta, 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.28 CAL Delta, jitter in S/PDIF data signal, 20Hz-50kHz, when transmitting music #1 (solid) and music #2 (dashed) (vertical scale, 1ps-2ns, 100µV = 1ps).

Next up is the Meridian Compact Disc Recorder (CDR), shown in figs.29 and 30. The silent track (solid trace) has a very low RMS level due to the inexplicable absence of any 7.35kHz subcode-induced jitter. The spectrum of the silent track does show some periodic jitter energy at 60Hz, 220Hz, 440Hz, and 700Hz. Except for the 60Hz power-line-induced jitter at 60Hz, these periodic components don't appear in the spectra when the CDR is playing music or sinewaves.

Fig.29 Meridian CDR, 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.30 Meridian CDR, 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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