Manufacturer's Specifications:
Frequency Response: 5 Hz to 20 kHz, ±0.5 dB
Dynamic Range: 90 dB.
S/N Ratio: 90 dB.
Total Harmonic Distortion: 0.01%.
Wow and Flutter: Unmeasurable.
Line Output Level: High, 3.0 volts; low. 600 mV.
Output Impedance: High, 600 ohms; low. 3.75 kilohms
Power Consumption: 40 watts.
Dimensions: 13 in. (33 cm) W x 5 3/8 in. (15 cm) H x 9-7/16 in. 24 cm) D.
Weight: 16 1/2 lbs. (7 1/2 kg.)
Price: Not established.
Company Address: 10 Sharp Plaza, Paramus, N.J. 07652, USA.
CD players are becoming familiar items in my lab. The latest one sent for evaluation was the Sharp DX-3. Physically more compact than the Technics SL-P10 tested last month, it is about the same size as the Hitachi unit evaluated two months ago and somewhat larger than the Sony CDP-101, the first CD player I tested.
In terms of configuration, the DX-3 is a front-loading player, much like the Technics and Hitachi units. Once it is switched on, depressing an eject button at the lower left of the front panel causes a hinged compartment to swing open. While the two other CD players employing this type of loading scheme had well-defined slots into which to drop a compact disc to be played, the Sharp unit seemed to have no well-defined location for the disc. Following instructions in the owner's manual, I casually dropped the disc inside the compartment, letting it fall where it might, and observing only that the proper (label) side faced me. Still following instructions contained in the manual, I lightly touched the "door." Much to my surprise it began to close, at the same time automatically orienting the d sc onto the spindle and changing the mode of the music-program display.
When the DX-3 is first turned on, the music-program display looks like a tape deck's bar-graph level meter, only calibrated from 0 to 60 minutes. A few seconds after the disc is loaded, the display changes to show one vertical bar for each selection on the disc, spaced in proportion to each selection's approximate length. When the disc plays: the bar corresponding to the present location of the laser servo on the disc flickers, while the bars preceding it glow. Other bar patterns show which selections, if any, are stored in the APMS (Automatic Programmable Music Selector) memory.
Two more digital displays are to the right of the disc compartment. The first of these shows the track number being played, while the second display shows the time, in minutes and seconds, which have elapsed since the beginning of that track.
Pushbutton controls along the lower right section of the front panel include "Repeat," "Reverse," "Forward," "Pause" and "Stop/Clear.' The "Reverse" and "Forward" buttons are used to perform what Sharp calls a "monitor search." When either of these buttons is depressed, play is interrupted and the laser pickup moves forward or back wards to other tracks. It is here, however, that I raise an objection to this machine's control arrangement: There is no way to listen to a given selection from its mid-point. If you depress the "Reverse" button, you will hear the current selection repeated from its beginning. The separate "Re peat" button is used to repeat-play an entire disc, over and over again, until that button is depressed a second time or the "Stop/Clear" button is. touched. The "Repeat" button can also be used in conjunction with the APMS to have only certain selections repeated.
Operation of the APMS feature involves the use of the four remaining small pushbuttons on the front panel. These are labeled "Memory," "Up," "Down" and "Clear." Operating much like the station preset memory systems found on recent FM/AM tuners, these buttons allow you to "program in" the track numbers you want to hear, in any order. The "Up" and "Down" buttons advance the track number display so that it shows the track you want. Depressing the "Memory" button retains that track number, and as many as 20 tracks can be programmed in this way. If a disc contains more than 20 tracks, APMS will not advance the pickup beyond the 20th track, though the "Forward" button will advance the pickup to all tracks. (I found this out pretty quickly, since the digital test disc I use contains 39 tracks, all of which are needed to test a CD player.) To the right of the track and time displays are indicator lights which tell the user, symbolically, that the player is in play, pause, repeat, or APMS mode.
The rear of the DX-3 has two sets of output jacks. One pair of terminals provides an output of around 0.5 volt and has a source impedance of 3.75 kilohms (at 1 kHz). The other set provides an output of nearly 3.0 volts, and a source impedance of only 600 ohms. Recommended load impedance in either case is 10 kilohms or greater. Other than this choice of outputs, there is no level control facility on the DX-3.
Sharp provided no circuit or design details concerning this CD player which, I understand, is one of several proto types that have been brought to the U.S. well in advance of actual market introductions here. (The units are becoming available in Japan.) It should be noted, however, that of the four CD players I have tested, this is the only one that arrived in its proper finalized shipping carton and accompanied by an actual published owner's manual, written in no fewer than seven languages! Clearly, Sharp is serious about bringing this product to market worldwide.
Measurements
Using the same test disc (Sony YEDS 2) which I used in my earlier tests of CD players, I repeated all the tests for the Sharp DX-3. Frequency response was flat within 0.1 dB from 100 Hz (the lowest spot frequency in the test disc) to 20 kHz. Stereo separation between channels measured 79 dB at mid-frequencies, decreasing to 75.5 dB at the bass test frequency and to between 54.5 and 60 dB (depending upon the channel measured) at the 20-kHz test frequency. These results are plotted in Fig. 1.
Fig. 1--Frequency response and channel separation.
Fig. 2--Harmonic distortion vs. frequency, at 0 dB level.
Harmonic distortion versus frequency, at 0 dB (maximum output) level, is plotted in Fig. 2. It ranged from an extremely low 0.005% at low frequencies, to a rather high 0.6% at 20 kHz. In fact, observing the nature of the "distortion" at 20 kHz on a 'scope, I concluded that this high reading was not really harmonic distortion at all, but rather a form of "beats" (probably against the sampling frequency or a subharmonic of it), not unlike the spurious outputs seen when measuring high-frequency distortion in the stereo mode of FM tuners. It would appear that even with CD players, you can't have everything. Note that the frequency response for the DX-3 was actually flatter at the high end than that of any CD player measured to date. This suggests that Sharp's anti aliasing filter may be tuned to a somewhat higher frequency.
The result is the higher order of apparent distortion (or spurious signal content) observed at 18 and 20 kHz.
The Sony test disc contains 1-kHz test tones at levels ranging from 0 dB (maximum digital recording level) down to -90 dB. These are used to check linearity of the play back system. The DX-3 was absolutely linear down to more than -60 dB. Where I should have read -80 dB, I read an output of -78.4 dB, but even this "error" was probably not caused by any departure from linearity but by the contribution of hum and/or noise supplied by the test-bench setup.
Signal-to-noise ratio, A-weighted, measured 93.5 dB. Without any weighting network, S/N measured 91.0 dB be low reference output (maximum) level. The SMPTE-IM distortion measured a rather high 0.67% at 0 dB output level but settled down to a negligible 0.05% at an output level of -10 dB. Using the twin-tone signals available on the test disc (19 and 20 kHz, at 0 and -10 dB levels), I measured a CCIF-IM distortion of only 0.002% at both record levels.
Standards for the CD audio disc call for specific values of de-emphasis to be built into the disc players. Three test tones contained in the test disc are used to verify the accuracy of this de-emphasis characteristic, and final lab measurements involved these test tones. Precise readings are supposed to be -0.37, -4.53, and -9.04 dB at 1, 5, and 10 kHz respectively. For the DX-3 I measured -0.4, -5.0, and -9.7 dB.
Use and Listening Tests
Having retained the few musical CD discs which were loaned to me for last month's review. I was able to compare the sonic performance of the Sharp with that of a previously tested player I'd also retained. In terms of sound quality. I could not detect any difference between the two units.
All of the programming and display features of the Sharp DX-3 worked perfectly and with reliable repeatability. I have already noted the fact that it is not possible to play a given track from its mid-point (other CD players tested so far can be instructed to start playing from any point on the disc). If this doesn't pose a problem for you, then the Sharp DX-3 can be ranked right up there with the previously tested Technics and Sony players. Much will depend, of course, upon what the final pricing of this unit (or, for that matter, the earlier tested units) will be. We won't know that until the first production units reach U.S. dealers' shelves. As for myself, having now had many, many hours "at the controls" of compact digital disc players, I can hardly wait to share my enthusiasm with the rest of you music lovers out there.
-Leonard Feldman
(Audio magazine, Mar. 1983)
Also see:
Technics SL-P10 Digital Audio Disc Player (Feb. 1983)
NEC CD-803E Compact Disc Player (Nov. 1983)
Sanyo DAD 8 CD player (EQUIP. PROFILE, April 1984)
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