Akai CD-D1 CD-player Review

The extensive automatic features and programmable operation of the Akai CD-D1 make it one of the most versatile Compact Disc players we have used. Like all CD players, the CD-D1 employs a laser light source and a photodiode pickup that “tracks” a spiral pattern of microscopic pits on a 4.7-inch-diameter disc. The electrical output of the pickup is in a digitally encoded form from which the original audio program can be recovered with almost total fidelity.

Most of the performance specifications of the CD-D1 are determined by the industrywide Compact Disc standard, so they are similar to those of other CD players. For example, its frequency response is specified as 20 to 20,000 Hz ±0.5 dB, its dynamic range, signal-to-noise ratio (S/N), and channel separation all as exceeding 90 dB, its harmonic distortion as less than 0.005 per cent, and its wow and flutter as essentially nil (the steadiness of playback pitch is ensured by a highly stable quartz-crystal oscillator).

Akai also specifies some of the approximate program-access times of the CD-D1, including a start-play time of 2 seconds and an average random-access time of 3 seconds. It differs from most current CD players in having sharp-cutoff digital output filters instead of the sharp-cutoff analog filters that other players use. Digital filtering reduces an otherwise unavoidable phase shift at the higher audio frequencies in the program playback. Whether there are any audible benefits to this lack of phase shift has yet to be decided by research.

The most obvious special qualities of the Akai CD-D1, however, pertain to the great operating flexibility provided by its built-in microprocessor controller. Besides being able to play up to twenty-four selections in a programmed order, the CD-D1 can cue up passages within any recorded selection according to the time in minutes and seconds from its start, and it can directly cue up passages identified on some discs by recorded index points. It also allows for “phrase repeat” play, which permits any portion of a selection to be defined and then replayed as often as desired, and automatic selection-repeat play in any of the cueing modes. Of course, the user can also instruct the unit to play any single selection on a disc by specifying its number.

About half of the front panel of the Akai CD-D1 is devoted to pushbutton controls and indicators for the programming functions, the other half to the disc-loading door. Pressing the stop/eject button causes the bottom-hinged door to swing open. The disc is inserted into a slot on the upper edge of the door, which must then be closed manually. Pressing the play/start button begins play at the beginning of the disc. The pause button stops and starts playback on alternate touches (but, unlike most LP record players, playback always resumes at the exact point where it was halted).

A four-digit display in the center of the panel normally shows the time in minutes and seconds from the start of the selection being heard, and above it another digital readout shows the selection number. Illuminated indicator dots in the time window denote indexed or memory-playback operation, and pressing a button marked total time changes the display to show the elapsed time from the start of the disc instead of from the start of the selection. Indicator lights above the selection display show whether the CD-D1 is in its play, pause, or standby mode (the last is when the player is cueing up a selection). A window above the time display contains a red LED that moves behind a ruler-type scale to show the relative position of the laser pickup head in its path across the disc.

Pressing the f.fwd or the f.rev button slews the pickup rapidly ahead or back; normal play is resumed automatically when the button is released. (No sound is heard in either fast-speed mode.) Two buttons are marked ipls (for Instant Program Locating System). A momentary pressure on the left-hand button causes the pickup to skip either back to the start of the previous selection on the disc (if it is pressed within the first 4 seconds of play of a selection) or back to the start of the same selection (if pressed more than 4 seconds into a selection). Pressing the right-hand button causes the pickup to skip to the start of the next selection on the disc. In the memory-playback mode, only the right-hand ipls button is operative, and pressing it causes the player to skip to the next programmed selection.

The right portion of the front panel contains ten memory-selection buttons (numbered from 0 to 9) and related controls. Up to twenty-four selections can be programmed for play in any order by pressing, in sequence, the correspondingly numbered buttons and the set button for each one. It is easy to check the program sequence by pressing memo call, which causes the numbers of the programmed selection to appear in sequence in the time-display window. The programmed sequence can be canceled by pressing the c/ac button. Other programming buttons include phrase (for the phrase-repeat function), index and time (for cueing), and repeat (which repeats a programmed sequence).

The rear apron of the Akai CD-D1 contains two audio-output jacks and a small knob that adjusts the output level. The exterior, including most of the main operating controls, is a satin-finished silver color, with the other control areas in dark blue and gray. The player measures 17-1/4 inches wide, 5-3/4 inches high, and 11-1/2 inches deep, and it weighs 16-1/4 pounds. Price: $1,000.

Laboratory Measurements.

The CD-D1’s playback frequency response, measured using the Philips Test Sample 3 (TS3) test record, was flat within +0.2, —0.3 dB from 20 to 20,000 Hz, with both channels having identical responses. The slight fluctuation took the form of a cyclic output variation over the full audio range, becoming more visible in the response curve at higher frequencies. This is a typical characteristic of CD players that use high-frequency digital filtering instead of an analog filter cutting ofif just above the audio range.

The maximum audio output from a 0-dB recorded level (the maximum possible from a digital disc) was 2.28 volts, with the channel levels matched within 0.12 dB. The 1,000-Hz playback distortion was measured with the Philips TS3 record at recorded levels of 0, —6, —12, and —24 dB (at lower recorded levels the minuscule distortion components were not discernible in the spectrum analysis of the signal). Referred to these output levels, the total harmonic distortion (THD) measured 0.0025, 0.0045, 0.0075, and 0.01 per cent, respectively. When these measurements are referred to the maximum (0-dB) output, the distortion percentages naturally come out lower, with a maximum value of only 0.001 per cent at the — 24-dB recorded level. Intermodulation distortion was measured at 0 and —20 dB with mixed test signals of 60 and 7,000 Hz. The respective readings were 0.005 and 0.02 per cent (again, the latter figure falls to 0.002 per cent if the measurement is referred to the maximum output).

The stereo channel separation was measured with the Sony YEDS2 test record at several frequencies from 100 to 20,000 Hz. Measuring in both directions (from left to right and from right to left), we found differences of from 2 to 9 dB between the two channels. The average reading ranged from a maximum of 98.5 dB at 1,000 Hz to a still outstanding minimum of 85.5 dB at 20,000 Hz. The signal-to-noise ratio (S/N) relative to 0 dB was 96.5 dB unweighted and 102 dB with A-weighting. The playback speed was exact, and the flutter reading was the residual of our meter, about 0.001 per cent.

All digital players (tape as well as disc) employ some form of error-correcting system to correct for a reasonable number (up to several thousand) of consecutive errors that could otherwise produce a highly audible noise. Since not all such systems are equally effective, this quality is one of the few genuine and meaningful distinctions between CD players.

One of the Philips test discs (TS4A) is a modified version of a musical sampler to which calibrated amounts of embedded signal-surface damage, opaque simulated external “dirt” spots, and a pattern of ruled lines that simulates a fingerprint have been added. By playing this record and noting the exact time at which a playback interruption is heard, it is possible to establish the amount of data interruption that can be corrected by the player’s circuits. The outer-surface “damage” on this record ranges from 300 micrometers, which should be playable by any properly functioning unit, to 800 micrometers, with which few players can cope. The Akai CD-D1 had a momentary “hang-up” during the 500-micrometer interruption caused by a surface spot and “stuttered” when playing a selection with a 600-micrometer interruption. The interruptions in the inner information layer range from 400 to 900 micrometers in length (the former should be within the capabilities of any properly operating player). The CD-D1 was able to play the 800-micro-meter interruption but had momentary drop-outs at 900 micrometers. There were no audible problems caused by the simulated fingerprint.

The mechanical tracking action of the laser-optical system was apparently well controlled, for moderate impacts on the top or side of the unit did not affect its tracking performance. Slewing from Track 1 to Track 15 of the Philips TS4 sampler took 6 seconds. The CD-D1 was able to make the transition from Track 17 to Track 18 of that disc with no clipping of the opening syllables on the latter track; since there is no quiet interval between these tracks, a player with “loose” servo control sometimes clips the start of Track 18 when cueing it up.

Comment

Only one aspect of the Akai CD-Dl's performance impressed us as at all worth criticizing: it repeats a disc indefinitely until the stop button is pressed— even when the repeat function has not been activated. While this operating quirk is mentioned in the manual, it is not emphasized, and it was a bit surprising. In any case, the manual should be read carefully by users who hope to get the most out of the CD-D1. Although it is easy enough just to load a disc, press play, and listen to it straight through, mastering the many special operating features that make this player so versatile takes a little study and practice.

In terms of its “sound,” all we can say is that the CD-D1 is certainly equal to any other CD player we have tested. This will surely be the rule in future tests as well, since all properly operating CD players necessarily sound virtually identical. Trying to describe sonic differences between them— let alone expressing a preference—seems pointless. Instead, we’d rather concentrate on tracking abilities and programming functions, in both of which the Akai CD-D1 clearly excels.

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