Sansui CD-X311 CD-player Review

During the past year, we have been hearing a lot about 1-bit digital-to-analog (D/A) conversion, developed more or less simultaneously in Holland and Japan by several companies, and a growing number of new compact disc players feature the technique. Last October we reported on Sansui’s first 1-bit CD player, the deluxe Vintage Series CD-X711, and now Sansui has incorporated 1-bit D/A conversion into a less expensive CD player, the CD-X311.

Briefly, the process—which Sansui calls the Linear and Direct Conversion System, or LDCS—involves digital oversampling, at a very high frequency, of the 16-bit digital signals derived from laser scanning of the microscopic pits on a CD. The result is a stream of constant-amplitude pulses, rather than a series of 16-bit digital “words” made up of groups of pulses, hence the “1-bit” designation. The duration (width) and density of the pulses are proportional to the instantaneous amplitude of the original analog signal, which can be recovered by filtering the series of pulses to remove the high-frequency components. Since the signal’s noise level is increased by the conversion system’s digital processing, a “noise-shaping” circuit shifts some of the noise energy upward in frequency, above the audio range.

A major advantage of the 1-bit conversion process is the virtually complete elimination of the amplitude errors commonly found in standard d/a converters at levels below —70 dB, allowing the very low inherent distortion of the CD system to be maintained at the lowest levels. It also permits a simplification of the player’s circuitry, reducing the cost to the consumer.

The Sansui CD-X311 is very similar to the earlier CD-X711 in its appearance and features, although it is lighter and less expensive. It can be programmed to play up to twenty tracks in any order or randomly. A COMPU-Edit feature automatically selects those tracks (up to twenty) that will fit on each side of a standard-length cassette, and the player pauses automatically at the end of the first side to permit the tape to be turned over. A numerical keypad provides direct access to any track, but there is no provision for cueing to numbered index points.

The display window shows the current track number and elapsed time on the track in large white fluorescent numerals. The start-up display shows the total number of tracks and playing time of the disc. A button switches the time display to the remaining time on the disc or in the current track. A music calendar shows the numbers of unplayed tracks (up to twenty). Symbols show the status of the transport functions (play, pause, etc.), and a vertical column of light bars shows the relative setting of the player’s volume adjustment (made from the remote control). A red alphanumeric display shows the status of the various special operating features.

The rear apron of the CD-X311 has a pair of analog audio output jacks and a coaxial digital output. A sync terminal is used to connect the CD-X311 to a compatible Sansui cassette deck for automatic tape dubbing.

The infrared remote control supplied with the CD-X311 duplicates most of its normal operating controls, including opening and closing the disc drawer. The principal omissions are the sync and auto-space buttons and the COMPU-edit function. On the other hand, the remote control has up/down buttons, not present on the player itself, to adjust the level at both the headphone and line outputs. The CD-X311 measures 17 inches wide, 12-1/2 inches deep, and 4 inches high, and it weighs just under 9 pounds. Price: $445.

Lab Tests

On our test sample of the CD-X311, the left channel had appreciably greater noise and hum levels than the right channel. Although its hum and noise were completely inaudible under any conditions (measuring about —90 dB), they were sufficient to affect some other measurements, such as low-level linearity. Therefore, where the channels differed appreciably, we have given only the figures obtained from the right channel.

The frequency response was within 0.08 dB overall from 20 to 5,000 Hz, rising to a maximum of +0.4 dB at 16,000 Hz (well within the rated ±0.5 dB). The de-emphasis response error ranged from —0.1 dB at 5,000 Hz to a maximum of 0.22 dB at 16,000 Hz. The channel separation was 99 dB at 100 Hz, 95 dB at 1.000 Hz, and 74 dB at 20,000 Hz. The A-weighted total harmonic distortion plus noise (THD + N) was — 89 dB (0.0035 percent) over most of the audio range, reaching its maximum of —80 dB (0.01 percent) at 15.000 Hz. The 1,000-Hz THD+ N was a constant 0.0035 percent from 0 to —65 dB.

The player’s low-level linearity dramatically demonstrated the capabilities of the 1-bit conversion system. With CD test signals between — 60 and —90 dB (undithered), the output readings differed from the nominal recorded level by only 0.2 to 0.3 dB. These readings are typical of the few 1 -bit machines we have tested so far and apparently represent the performance to be expected from this class of product.

The interchannel phase shift reached its maximum of —1.4 degrees at 20,000 Hz. The dynamic range (EIAJ method) was 97.1 dB, and quantization noise was —90.5 dB. Wide-band noise was —106 dB. A spectrum analysis of the noise during playback of an “infinity zero” track (no recorded signal) showed a linear decline, from — 110 dB at 20,000 Hz to — 132 dB at 30 Hz. Power-line hum products did not exceed the noise level by more than 2 or 3 dB. The frequency (speed) error was +0.0021 percent.

The slewing time of the laser pickup was about average, with 2.5 seconds required to go from Track 1 to Track 15 of the Philips TS4 test disc. The player was able to track the Pierre Verany #2 test disc through its 1,000-micrometer defects but mistracked at the 1,250-micrometer level. It was moderately sensitive to impact on the top cover, mistracking with fingertip tapping, but was less sensitive on the sides. The headphone volume was very good, among the loudest we have yet heard from a CD player.

Comments

The Sansui CD-X311 is an excellent illustration of how much improvement in value and performance we can expect as 1 -bit d/a conversion becomes more widespread. Virtually identical to the company’s Vintage Series CD-X711 in features, it manages to come surprisingly close to the more expensive model in its performance as well. It even has the same powerful headphone output that distinguished the CD-X711 from most other players. The most obvious differences between the two lie in their construction. The solidity and weight of the CD-X711 cost money, and undeniably its measurements are for the most part somewhat better.

But that is not a fair comparison. If you compare the CD-X311 to other CD players, at any price, that use conventional (ladder-type) D/A converters, the difference in low-level linearity measurements is striking. The audibility of this improvement may be arguable, but not that it is an improvement.

We found no unexpected bugs in the operation of the Sansui CD-X311. Its major omission, in our view, one that it shares with the vast majority of CD players at all price levels, is that there is no way to access numbered index points directly. There is not even a number on the display to indicate the current index number. But if that is not important to you, the CD-X311 is surely a fine CD player.

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