California Audio Labs CL-20 DVD-V/CD player Measurements

Sidebar 3: Measurements

Perhaps because it uses a DVD transport, the CL-20 offered superb error correction. It played without a glitch through the Pierre Verany Test CD's track 35, which has a 2.4mm gap in its data spiral, breaking up only on track 36. However, its use of a single CD-compatible DVD pickup meant that I couldn't assess its jitter: the test signals for the Miller Audio Research Jitter Analyzer are carried on a low-jitter CD-R, which couldn't be recognized by the CAL player.

The maximum output from the analog jacks was a fraction of a dB above the CD Standard level of 2V at 2.08V, this sourced from a low 30 ohms across the band. The analog output was noninverting. The frequency response from CD is shown in fig.1. (The response with de-emphasis is identical, so is not shown.) There are slight rises at the band edges. I couldn't assess the frequency response at the 96kHz sample rate because a suitable test disc is not yet available. However, the Chesky "Super Audio Collection & Professional Test Disc" DVD (CHDVD171) has test signals recorded at both 48kHz and 96kHz sample rates. Figs.2 & 3 show the waveforms of a 1kHz squarewave at 0dBFS, replayed from the CAL CL-20 at 48kHz (fig.2) and 96kHz (fig.3) rates. The period of the ripples overlaying the waveform tops can be seen to be half as long with the higher sampling rate. There is a little more leading-edge overshoot, however, which suggests a slight peak in the ultrasonic frequency response.

Fig.1 California Audio Labs CL-20, frequency response at 0dBFS (right channel dashed, 0.5dB/vertical div.).

Fig.2 California Audio Labs CL-20, 1kHz squarewave at 0dBFS, 48kHz sampling.

Fig.3 California Audio Labs CL-20, 1kHz squarewave at 0dBFS, 96kHz sampling.

When I tried to measure its channel separation, I found that the CL-20 was very sensitive to grounding. It gave the lowest levels, both of power-supply hum and of general audio-band garbage, when it was not grounded to the Audio Precision test system at all. This suggests that it may misbehave with some preamplifiers. The crosstalk, however, was very low, at better than -100dB below 1kHz and around -87dB at 20kHz.

The low level of noise with the grounds lifted can be seen in fig.4, which is the spectrum of the CL-20's analog outputs while it decodes CD data representing a dithered 1kHz tone at -90dBFS. The trace is free from high- and low-frequency spuriae, which has not been true for the mass-market DVD players I have examined. Fig.5 shows a similar spectrum with the bandwidth extended to 200kHz and a test signal of digital silence. There is a broad peak centered on twice the CD sampling frequency, but this is still quite low in absolute level.

Fig.4 California Audio Labs CL-20, spectrum of dithered 1kHz tone at -90.31dBFS, with noise and spuriae, 16-bit data.

Fig.5 California Audio Labs CL-20, spectrum of digital silence with noise and spuriae, 16-bit data (1/3-octave analysis, right channel dashed).

The California Audio Labs player offered excellent linearity, if not quite to the standard featured by the Arcam Alpha 9. Fig.6 reveals that any level error is negligible down to -100dBFS and exceeds 2dB only below -105dBFS. The waveform of an undithered 1kHz sinewave at -90.31dBFS (fig.7) is correspondingly well defined and relatively free from noise. This is a high-resolution CD player. [It should be noted that the CL-20 will only pass 20-bit data from its digital output.—Ed.]

Fig.6 California Audio Labs CL-20, left-channel departure from linearity. (2dB/vertical div., right channel dashed.)

Fig.7 California Audio Labs CL-20, waveform of undithered 1kHz sinewave at -90.31dBFS (16-bit data).

Distortion was also very low, as shown in fig.8, the spectrum of a 61Hz tone at full level. Only the second harmonic is evident, but this is at -96dB! Intermodulation was also very low, evidenced by the 1kHz difference component in fig.9 lying at just 0.01% (-80dB).

Fig.8 California Audio Labs CL-20, spectrum, DC-1kHz, 61Hz at 0dBFS, 100k ohms load (linear frequency scale, 20dB/vertical div.).

Fig.9 California Audio Labs CL-20, HF intermodulation spectrum, DC-22kHz, 19+20kHz at 0dBFS, 100k ohms load (linear frequency scale, 20dB/vertical div.).

The ability to play DVDs as well as CDs has apparently not compromised the CL-20's performance as a CD player, which cannot be said of some of the mass-market DVD players that have passed through Santa Fe.—John Atkinson

California Audio Labs
P.O. Box 1218, 113 Taylor Way
Blue Lake, CA 95525
(707) 668-1736
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