NEC CD-810 CD-player
The no-nonsense quality that characterizes NEC designs is much in evidence in the CD-810. It's a solid performer that is dignified in both styling and behavior. The features appear to have been soberly considered, and, despite the unusual nature of some of them, the impression is not one of glitziness. Also typical of NEC-which is as well known for its sophisticated integrated circuits and computers as it is for home entertainment components- are the high-tech touches with which it seeks an ever-closer approach to sonic perfection.
Of all these touches, NEC seems most proud of its proprietary output filtering system. Two filters are involved: In the digital domain, there is a 73-tap ND (non-delay) filter, which is supplemented by an FDNR (frequency-dependent negative resistance) low-pass filter. (Impressive as it sounds, FDNR is just a way -uncommon in audio-of hooking up common operational amplifiers, resistors, and capacitors into a filter circuit.) The filters, in combination with two-times oversampling and dual digital-to-analog converters, are credited with exceptional accuracy in waveform reconstruction.
Similarly high-tech is the optical internal coupling that helps minimize the possibility of interference between analog and digital sections, as do the separate power supplies for the digital and analog sections. The CD-810 also is among the NEC models incorporating a phase-inverter (or polarity-inverter) switch so you can maintain absolute phase even when the recording-or the remainder of your system-flips it. This, however, presumes that either you can discern an audible difference between polarities and can tell which setting is correct (not easy) or that you have some previous knowledge of the polarity of the original recording.
There are a number of unusual operational features as well. Of these, the most striking are certainly the editing modes used for making cassette dubs of CDs. In the automatic editing mode, you use the keypad to punch in the time available on each side of the cassette (45, for example, to stipulate one side of a C-90). The CD-810 programs itself for all of the tracks, beginning at the first track and continuing until there's not enough time left for the next unprogrammed track. If you press the editing button a second time, the player will program the second side, beginning where the first left off and inserting a pause between sides in the sequence, to give you time to turn over the cassette.
If you already have something recorded on Side A of the tape, you can set the player to program for just the remaining time on that side, then the full time on Side B. If you don't want to start at the beginning of the disc, you can cue up the track you want to start with before beginning automatic programming. You can also use a manual editing mode and program the sequence yourself in any order. As you do, the display keeps track of the time still available on the tape so you can tell which tracks will fit and which won't. When the editing is done, you simply start the recorder and the 810 together. For programmed playback only (without taping), a 24-selection memory is provided.
Also unusual, though without the obviously broad application of the editing functions, is timer search. When this function is invoked, the keypad can be used to stipulate an elapsed time from the beginning of a track to the point at which you want playback to begin. This function is available only via the supplied AR-810 wireless remote control. So is the polarity-inversion function, though activation of both functions is indicated by pilot lights on the player's front panel. The remote, which is powered by two AA cells, also incorporates basic transport controls (even an open/close for the disc drawer) and those for the memory-playback and repeat functions.
Whether set at the remote or at the front panel, the CD-810 offers the usual repeat-mode options: full disc, programmed sequence, or A-to-B looping. The transport functions include audible search, bidirectional seek (skip), index seek, and (on the front panel only) intro scan. The ability to cue up to index points on CDs that are indexed is always welcome. The intro scan is set to sample the first 10 seconds of each track as a default but can be adjusted (once again, using the front-panel keypad) to any sample length from 1 to 60 seconds-a feature we haven't seen before on a Compact Disc player (or anything else for that matter).
There is also a spacing function to add a few seconds between tracks (handy if you're going to be playing a dub on a programmable cassette deck that needs good, clean spaces in order to pick up its cues) and timer playback. For the latter, simply leave a disc in the drawer and the power switch on; when power is restored via the timer, the disc automatically begins playing from the beginning.
The display is exceptionally neat, considering the large amount of information it imparts. The left side is the increasingly common calendar-style display that indicates available or programmed tracks (as many as 20, with an extra element that lights when a higher number is involved) and extinguishes the track numbers as they are played. Down the middle are indicators for major functions (memory, editing modes, et al.) and the four time-display options (elapsed in the current track, total elapsed, remaining in the current track, and total remaining). The time display itself is to the right, above the indicators for the repeat modes, intro scan, and the spacing function. Track and index numbers (or item number, in programming) are displayed at the top of this section. The front panel's headphone output has its own volume control.
The first thing we looked at in Diversified Science Faboratories' data was the frequency-response curves. NEC claims exceptional freedom from ripple in its filter design; indeed, even the lab's expanded traces show no aberration that could be attributed to ripple. The efficiency of the filter design is further confirmed by the well-controlled ringing in the square-wave and pulse waveforms. Curiously, the slight rolloff at the very top of the audio band doesn't assume quite the same contour in the two channels, but response is too flat and smooth to lend any importance to such quibbles. Response with de-emphasis is more accurate than usual.
Distortion figures are excellent: below our reporting threshold (0.01 percent) in all the intermodulation measurements and in all the harmonic distortion measurements at 0 dB. And at -24 dB, THD was only marginally above the threshold, meaning that it's far below the audibility threshold. The linearity figures go slightly awry at extremely low levels (-80 dB, in particular), but not by as much as we often encounter. In any event, the discrepancies are not great enough to be of audible consequence.
The CD-810 negotiated all of the tracking tests flawlessly, as most (but certainly not all) players do these days. Headphone output clipped at a generous 7.63 volts into an open circuit, although with the standard 50-ohm load (which is more representative of actual headphone loading), it clipped at just under 1 volt, which is somewhat low. The importance of this limit obviously will depend on the impedance and sensitivity of the headset you use with the player, but we wouldn't expect it to pose a problem under most circumstances.
The CD-810 is unquestionably a fine performer, and it's clear that care and ingenuity have gone into its many features. Less apparent is the quiet, ergonomic grace with which it performs its functions. Using it is a pleasure in every respect.
