Toshiba SD-3006 DVD-player Review
Toshiba developed many of the core technologies behind the DVD system, so we were more than normally excited by the arrival of one of its DVD players for testing. That player, the SD-3006, is the more expensive of Toshiba's first two models. It has two parallel-driven pairs of analog RCA-jack audio outputs. You get stereo audio out of them when you play a CD and Dolby Surround matrix-encoded two-channel audio when you play a multichannel DVD. (The conversion from DVD's discrete multichannel format to matrix signals that can be decoded by a Dolby Pro Logic decoder is performed internally.)
If you are blessed with a system containing a Dolby Digital decoder, you can get full multichannel DVD audio by hooking the player's PCM/ AC-3 coaxial digital audio output to the device containing the decoder. You have to turn the analog outputs on or off with a rear-panel switch; which setting you should use depends on your hookup and whether your system can perform Dolby Digital decoding. There is no optical digital audio output, nor, for that matter, a headphone output.
On the other hand, the SD-3006 is one of the very few DVD players equipped with component-video outputs. (The $599 SD-2006 does not have component-video outputs and offers only one pair of analog RCA-type audio outputs.) If you have a monitor that can accept these signals - some very expensive front-projection TV systems and professional studio monitors can - they will provide the best possible DVD picture quality since the signal paths between a player's component-video outputs and the picture tube are subject to the least amount of processing, which can degrade quality. Second best, and it's a very close second, is the video quality provided by the SD-3006's S-video output. Last comes the standard composite-video output. With this player you have to choose, again via a rear-panel switch, between using either the component-video outputs or the other two; when the S-video or composite-video outputs are on, the component-video outputs are off.
When it comes to disc-navigating features, the SD-3006 is better equipped than the other DVD players we've seen, top-of-the-line or not. It has two fast-scan speeds (twice and eight-times normal), three slow-motion speeds (half, one-eighth, and one-sixteenth normal, forward only), and still-stepping (forward only). Cueing a title, chapter, or CD track can be performed using the remote control's numerical keypad to enter cueing points directly. The player understands both common syntaxes for selecting track No. 10 and later tracks: Press the +10 key, or enter each digit individually. Nice.
Repeat modes include title, chapter/ track, and A-B segment. Programmed playback is available for as many as thirty program segments, and the sequence can be displayed on screen. The SD-3006 also has the standard facilities for selecting subtitle display, subtitle language, on-screen-display language, aspect ratio, camera angle, and parental lockout.
Front-panel controls are extremely basic: power on/off, drawer open/close, stop, play, pause, and track/chapter skip forward and backward. The remote contains all the other controls. Its numerical keypad, unfortunately, is underneath a sliding panel, as are the slow-motion, programming, and repeat controls. The remote's exposed buttons are gratifyingly differentiated by size, shape, color, and location, which makes it one of the best DVD remotes on the market so far.
The SD-3006 is one of those DVD players that will not play a recordable CD (CD-R) - it won't even acknowledge the presence of a CD-R in its disc drawer. Since our special homebrew CD-player test signals are still available only in that disc format, I had to improvise with the few dithered test signals scattered over various commercial test CD's. Our excess-noise measurements were made with Dolby Lab's new Dolby Digital test DVD. The excess-noise test signals were encoded in the Dolby Digital system's two-channel mode (as opposed to the more familiar 5.1-channel mode). Unlike our test CD-R, which contains a quasi-20-bit test signal incorporating noise-shaped dither, the Dolby test disc's 18-bit and 20-bit signals, when decoded properly by a DVD player's internal Dolby Digital circuitry, produce signals of true 18- or 20-bit resolution without the use of noise-shaped dither. Our excess-noise calculations have been adjusted accordingly. The results indicate that the player has a background noise level typical of a digital-to-analog (D/A) converter with resolution a little better than 16 bits. Our standard A-weighted noise test had to be finessed by using the last few seconds of a fade-to-dither test on the CBS CD-I test disc, which is available only in the de-emphasis-off (normal) mode.
The Dolby test DVD also enables testing of video interference leaking into the analog audio outputs. Over a background of 20-bit dither, the disc cycles through a series of video test patterns whose signal leakage can cause audio side effects (at least they would with a laserdisc or VHS Hi-Fi tape). The SD-3006 did extremely well in this test, showing no change in noise level with each change of video pattern. (I can't wait to try this with other players.) On the whole, then, the SD-3006's analog audio outputs were quite clean and comparable to those of a typical CD-only player of the same price.
Missing from our data is a full set of video measurements of the kind we used to make on laserdisc players. The main reason for this is the lack of a suitable test DVD: one whose video test patterns are known to be of digital origin, of verifiable quality to begin with, and of sufficient variety to test all the relevant parameters. The one "test" disc we did have was more of a demo DVD made by Sony and intended for letterbox playback. This disc did turn up a couple of minor video problems with the SD-3006.
On what we now consider one of the acid tests of a DVD player - a continuous gray scale, which produces a screen that is black at the left and goes through every shade of gray to end up white on the right - the SD-3006 produced faint vertical bands, which indicate nonlinearity in the video D/A converters. The bands were particularly evident on the left, darker side of the test pattern, where nonlinearity is more visible than in brighter areas. Sure enough, a waveform-monitor examination of all of the player's outputs (composite, S-video, and component) showed areas of "non-monotonicity" where the video D/A waveform remained level when it should have been rising.
Nevertheless, the Toshiba player's video D/A nonlinearity was invisible as such in normal program material. Actually, it was about par for the course; we've seen only one player with superior performance and one player that was decidedly worse. When video D/A nonlinearity is severe, it is most easily seen as weird "contouring" effects during fade-ins and fade-outs. We saw none of this with any of the movies we played on the SD-3006.
In what is turning out to be another acid test for a DVD player - horizontal resolution - the SD-3006 produced more anomalous results. While the player did manage to generate visible detail at the limits of the Sony DVD's test patterns (approximately 480 lines of horizontal resolution from all outputs), the high-resolution test patterns were contaminated by spurious video frequencies. These showed up as larger-scale vertical striping superimposed on the fine-pitched vertical stripes of the resolution tests. The effect looked like the video equivalent of digital audio "aliasing," in which spurious low frequencies are generated by too low of a sampling rate. There is ample opportunity for aliasing or similar effects to occur in a DVD player in the extensive processing that converts the recovered MPEG-2 video data into conventional video signals.
This problem was not obviously visible with the normal movie program material we played, even with scenes containing elements chosen for their resemblance to the test patterns: Bill Paxton's jacket in Twister and Dorothy's tightly checkered dress in The Wizard of Oz. These images did sometimes produce moire effects, but most of those were probably caused by limitations in the television scanning process, not any performance deficiencies of the SD-3006. (You can also expect occasional cross-color "rainbow" effects with such tightly patterned images if you use the player's composite-video output.) Still, the "aliasing" problem originates with the player and not the test disc, as we have seen much better resolution-test performance from other DVD players of different brands when using the Sony test disc. And we cannot rule out the existence of cinematic images where this effect will be as obvious as it was with test patterns.
In other video areas, the SD-3006's performance was just about average for a DVD player, which means obviously superior to even the best laserdisc players and absolutely superb compared with VHS VCR's. Color accuracy was as good as that of our lab's video test-signal generator, and luminance and chrominance noise levels were very low.