Toshiba SD-9200 DVD-Audio/Video player Measurements

Sidebar 2: Measurements

The Toshiba SD-9200's maximum output level of 2.203V was 0.84dB higher than the CD standard's 2V, and the unit appeared to invert signal polarity. Its output impedance was a fairly low 353 ohms at 1kHz and above, rising inconsequentially to 360 ohms in the low bass. Error correction for CD playback was good, if not up to the standard I have found with some other DVD players. The output didn't suffer from dropouts until track 31 on the Pierre Verany Test CD, which has 1mm gaps in the data spiral.

The frequency response for CD playback was flat within the audioband (fig.1), with no de-emphasis error apparent with pre-emphasized discs. The bass rolled off very slightly early, but at -0.5dB at 10Hz, this will probably have no subjective consequences. Channel separation (not shown) was superb, at better than 120dB above 100Hz.

Fig.1 Toshiba SD-9200, frequency response at -12dBFS, without emphasis (top) and with emphasis (bottom). (Right channel dashed, 0.5dB/vertical div.)

The two pairs of traces in fig.2 show spectral analyses of the SD-9200's output while it decoded 16-bit CD data representing a dithered 1kHz tone at -90dBFS (top), and 24-bit DVD-V data (also representing a 1kHz tone at -90dBFS), though I suspect the latter is actually undithered. The increase in bit depth results in an 18dB increase in dynamic range in the treble, suggesting 19-bit resolution, which is excellent. However, some low-level power-supply spuriae limit resolution in the bass, with the left channel being worse than the right.

Fig.2 Toshiba SD-9200, 1/3-octave spectrum of dithered 1kHz tone at -90dBFS, with noise and spuriae (from top to bottom): 16-bit CD data, 24-bit DVD data (right channel dashed).

A peak at 16kHz can also be seen in both channels for DVD playback; this is suspiciously close to a TV monitor's line-scan frequency, and may have resulted from noise being picked up from the TV I used to navigate the Chesky Test DVD's onscreen menu. It was absent from the wideband spectral analysis I performed on the Toshiba's output while it decoded "digital black" from a CD (fig.3), when the TV was turned off. However, the noise floor in this graph seems improbably low for 16-bit data; I suspect that, to give the best possible reading, the player turns off its analog outputs when it detects this unique signal. The only other test signal I had handy was a digital DC offset of 1LSB, which usually doesn't turn off player outputs. However, this gave an identical spectrum, suggesting that the SD-9200 turns itself off with this signal also.

Fig.3 Toshiba SD-9200, 1/3-octave spectrum of "digital black" with noise and spuriae, 16-bit CD data (right channel dashed).

However, linearity error with 500Hz CD data (fig.4) was very low down to well below -110dBFS, correlating with the low noise floor seen in fig.2. As a result of the low noise and excellent linearity, the Toshiba's reproduction of an undithered 1kHz sinewave at -90.31dBFS (fig.5) was almost perfect, marred only by the negative-going halves of the waveform being very slightly smaller than the positive-going.

Fig.4 Toshiba SD-9200, right-channel departure from linearity, 16-bit CD data (2dB/vertical div., right channel dashed).

Fig.5 Toshiba SD-9200, waveform of undithered 1kHz sinewave at -90.31dBFS, 16-bit CD data.

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