Panasonic LX-700 Laserdisc player
Standing at the top of Panasonic's line of combi-players, the LX-900 incorporates quite a few features designed to enhance both audio and video performance. It also has many features designed to improve operating convenience, the two most important of which are automatic laserdisc side-changing and a digital frame memory that makes possible the complete range of viewing tricks (still-frame, slow motion, and so forth) for both types of laserdisc (standard-play CAV and long-play CLV).
Other important features include special measures to reduce video noise (a digital time-base corrector and a three-mode digital field noise-reduction system), MASH one-bit dig-ital-to-analog (D/A) converters for playback of CD's and digital laserdisc soundtracks, and a jog/shuttle search control for both CD and laserdisc playback. Less important features include a bizarre Video Select button on the remote that enables you to change from standard operation to the curiously named Retro mode, which essentially makes the picture black-and-white, and the Night viewing mode, which slightly reduces overall picture brightness. The LX-900 also has a complete array of the more-or-less standard CD/laserdisc cueing and repeat functions (except that you can't cue by CD index number) and two sets of RCA-jack outputs for composite video and stereo audio.
Although the LX-900 has two S-video outputs (fed from a digital color-separation circuit) and one optical digital-audio output, it is supplied without cables for them. Is that any way to promote these beneficial features? Does it encourage the purchase of other components with S-video or optical digital-audio connectors? And where can the average American buy such cables? They practically grow on trees in Japan, but I couldn't find a listing for either variety in a 20-minute search of the entire 1993 Radio Shack catalog. But enough of that-on to happier matters.
The LX-900's digital-audio performance was magnificent. Total harmonic distortion plus noise (THD + N), for example, was less than 0.0058 percent below 4 kHz, rising to a still inaudible 0 0.02 percent at 20 kHz. Noise was also 1 extremely low, although we were surprised to see that it dropped only 1 dB 8 when de-emphasis was activated S (some CD's are made with a high-frequency pre-emphasis that must be reversed in playback to achieve flat frequency response). Noise actually increased by 5 dB when the player was put into pause, possibly indicating that its D/A converters mute their outputs when playing the standard signal-to-noise test tracks, which contain only strings of digital zeros.
A more realistic noise and distortion test, spectrum analysis of a dithered 1-kHz tone recorded at -100 dB, showed-apart from the expected dither noise at around -128 dB across the audio spectrum-only traces of power-supply hum (at 60 and 120 Hz) and what might have been leakage of the video horizontal-scanning frequency (around 15.75 kHz). Since these individual components were all - 113 to -114 dB below full output, they, too, would be inaudible at normal listening levels.
D/A linearity, measured with a 1-kHz sine wave that decays slowly from -60 to -120 dB, was also excellent, with deviations of less than 0.2 dB down to -100 dB and greater than 0.5 dB only at levels below -103 dB, where noise started to predominate.
Only in frequency response did the LX-900's measured performance fall short of near-perfection. Response without de-emphasis was very flat (to better than 0.05 dB) from 20 Hz up to 2 kHz, rose slowly to +0.275 dB at around 12 kHz, and then rolled off more swiftly to -1 dB at 20 kHz. Deviations of those magnitudes in those frequency ranges should not be audible with music. With de-emphasis switched in, however, response shelved down above 1 kHz, dipping to -0.5 to -0.6 dB between 4 and 7 kHz. In absolute terms, this, too, is a small deviation, but it extends over a wide enough range at frequencies where the ear is very sensitive that it could be audible with some music in direct comparison with a player having flatter de-emphasized response. It's curious that we still see errors of this magnitude in CD and laserdisc players, since de-emphasis can be performed simply and with much higher precision as part of the digital signal processing (DSP) that most one-bit D/A converters have to perform to work at all. On the other hand, few recordings (most of them classical) are being made with pre-emphasis, so for most discs de-emphasis accuracy is irrelevant.
Performance with AFM-encoded laserdisc soundtracks was by comparison pretty awful: A 100-percent modulated 1-kHz tone produced distortion of 0.5 percent, and the A-weighted signal-to-noise ratio (S/N) was 75 dB. But those readings are par for the AFM-soundtrack course and important only when you play old laserdisc pressings that lack digital soundtracks or those that have alternative AFM soundtracks different from the digital ones. (Inclusion of AFM soundtracks on laserdiscs is scheduled to become optional sometime next year.)
The LX-900 reproduced the full range of laserdisc video test patterns extremely well. Off-the-screen horizontal luminance resolution, judged by viewing a wedge test pattern, exceeded 350 lines, slightly surpassing on direct comparison the abilities of the LX-900's predecessor, the LX-1000. This result was confirmed by luminance frequency-response measurements indicating a - 3-dB bandwidth of 4.6 MHz, which calculates out to 368 lines.
The player exhibited some luminance nonlinearity, which was worst at the lowest picture levels (the maximum nonlinearity of +7.5 percent occurred at the 10- and 20-percent picture levels) and declined steadily at higher luminance levels. This error may produce a slight loss of detail in dark areas of the picture, although no obvious effects were visible. All laserdisc video measurements should be taken with a grain of salt, however, since they vary according to the test disc used. The numbers cited here are the best-case results obtained from four different test laserdiscs.
The LX-900 seemed to be better than the LX-1000, and many other players, at suppressing the various low-level interference patterns the laserdisc system is prone to. Video noise on such things as color bars and full-field colors was very low, and that was with the Field Noise Reduction control at its standard setting. Higher settings gave a slight further reduction of color noise with only slight picture blurring at the highest setting. I found the B&W (Retro) and reduced-brightness (Night) options of the Video Select control pretty useless.
Operational annoyances were few. The most significant one I discovered was that it is impossible to prevent the LX-900 from automatically going to the second side of a laserdisc after finishing the first: You have to intervene manually to stop playback before the changeover starts. While this is the raison d'etre of the side-changing mechanism, the LX-900's uncontrollable enthusiasm in this regard can get irritating, especially with programs occupying an odd number of disc sides or when you're trying to cue to a point near the end of a side.
Other ergonomic problems were minor and principally concerned the remote control. The useful video noise reduction can be activated only from the player's front panel, whereas the particularly uninteresting Video Select and some other "trick" features (Strobe, Still & Sound) get buttons on the remote. Mechanical noise was lower than with the last Panasonic combi-player we tested (the manual-turnover LX-101), but the groaning gear-shifting we heard during the laserdisc side-changing process could prove distracting.
As usual, it would have been nice to have had further differentiation of the size, shape, and feel of many of the handset buttons. For example, the Mode button-controlling whether you are cueing by laserdisc frame or chapter number-could receive far more prominence than it does. And I think that the numerical keypads on the remotes for all CD and laserdisc players should enable direct numerical entry of track numbers greater than 9 instead of requiring repeated presses of a +10 button like the LX-900 does. Many laserdisc programs and classical CD's have dozens of tracks, and they'd be easier to get to with direct numerical entry. Finally, the remote-sensor window on the front panel should have been located where it would not be shadowed by an open disc drawer when the player is placed below the level at which you hold the remote (near the front-panel jog/shuttle control would have been a good place).
The standout among the LX-900's operational improvements is Panasonic's elimination of the traditional on/off button for the remote handset's jog/shuttle dials: They are always immediately operational. This may seem minor if you haven't used such controls before, but removal of this pointless button is actually a major advance in convenience. Trust me.
Working hand-in-hand with the jog/shuttle controls is the LX-900's most important video convenience feature: frame memory. Just as I would never buy a home CD or laserdisc player without a remote control, I wouldn't buy a laserdisc player without frame memory. It brings slow motion and freeze frames to CLV discs, and you can easily save more than the price premium of the memory by buying the considerably less expensive CLV versions of laserdisc movies.
On the whole, the LX-900 is a smoothly operating combination CD/laserdisc player that delivers superb video and digital-audio performance. Now, if I could only find an S-video cable....
