Technics DVD-A10 DVD-Audio player Measurements

Sidebar 3: Measurements

There's no such thing yet as a test DVD-A, so I checked the Technics DVD-A10's performance using a miscellany of test CDs and the Chesky Test and Sampler DVD-V, which has 24-bit test tones recorded (by Kevin Halverson of Muse Electronics) at 48kHz and 96kHz sample rates. The Technics doesn't play CD-Rs, so I couldn't check its jitter behavior with the Miller Audio Research Analyzer. All measurements were performed on the two-channel outputs.

The maximum output level was 2.153V, 0.66dB higher than the CD standard of 2V RMS. The output didn't invert absolute polarity and the source impedance was 1000 ohms at 20kHz, rising slightly to 1025 ohms at 1kHz and 1037 ohms at 30Hz. Error correction was not as good as I've measured from other DVD players; the 'A10 skipped on the Pierre Verany Test CD's track 30, which has 0.75mm gaps in the data spiral.

The Technics' frequency response for CD replay was flat within the audioband (fig.1), and de-emphasis was perfect. Channel separation (not shown) was superb, at better than 110dB below 1kHz, with a capacitive rise of 6dB/octave above that frequency.

Fig.1 Technics DVD-A10, frequency response at 0dBFS (right channel dashed, 0.5dB/vertical div.).

Fig.2 shows 1/3-octave spectral analyses of the DVD-A10's analog output while decoding a 16-bit dithered tone from the CBS Test CD (top traces) and the Chesky Test DVD-V (bottom traces). The traces overlap in the low frequencies and are dominated by residual power-supply noise at 60Hz, 120Hz, and 180Hz. (All these 60Hz-related spuriae are at or below -110dBFS, which is pretty good, if not as deathly quiet as the best CD playback systems.) In the midrange and treble, the increase in word length drops the noise floor by up to 12dB, implying an absolute performance for the Technics player of around 18 bits, which is good.

Fig.2 Technics DVD-A10, 1/3-octave spectrum of dithered 1kHz tone at -90dBFS, with noise and spuriae, 16-bit data and 44.1kHz sample rate (top); 24-bit data and 48kHz sample rate (bottom). (Right channel dashed.)

To generate the bottom traces in fig.3, the Technics decoded 16-bit data representing "digital black." The noise is significantly lower than with even the 24-bit data in fig.2, suggesting that the analog output actually mutes when the player detects this unique signal. The top two traces in fig.3 were generated using a -1LSB DC signal; ie, the same signal as "digital black," but offset in the negative direction by one least significant bit. The DVD-A10 has lifted the mute, which raises the noise floor by 15dB. The ultrasonic noise peak between 100kHz and 200kHz reveals the use of a delta-sigma noise-shaping DAC topology. The presence of a similar noise peak with what must be a muted condition is puzzling, however.

Fig.3 Technics DVD-A10, 1/3-octave spectrum of "digital black," with noise and spuriae (top); and of -1LSB DC data (bottom), 16-bit data (right channel dashed).