Sony CDP-X55ES CD-player Review

Sony’s CDP-X55ES CD player is a new member of the company’s ES series of deluxe audio components. In its circuitry and operating features, it represents a distinct advance over previous Sony models.

Like other ES components, the CDP-X55ES is mechanically rugged, with a heavy cabinet and a copper-plated metal chassis. For maximum immunity to vibration, the playing mechanism is mounted on a special base of a marble-like resin reinforced with glass fiber. The disc tray is constructed of the same material, and the mechanism itself is an aluminum die-casting.

The electronic features of the CDP-X55ES are equally unconventional. Sony’s fourth-generation LSI (large-scale integration) chips provide a number of special and useful functions. For instance, the Peak Search feature scans a disc rapidly to locate the highest peak signal level in the recording. It then plays a few seconds of the portion containing that level a number of times so that playback or recording levels can be set.

The player’s otherwise conventional twenty-four-track random-access programming mode is unusual in that the programmed tracks can be located on as many as six discs. After each disc is played, the display prompts you to load the next disc in the sequence. There is also a Time Edit feature that automatically selects tracks for tape dubbing so as to fit the maximum number on each side of a C-46, C-60, or C-90 cassette.

The CDP-X55ES features Sony’s Custom File system, which enables the user to store in the player’s memory a variety of programming instructions and preferred control settings for individual discs, recalling them automatically every time one of those discs is loaded and played. For instance, you can store the desired output setting at the variable-level and headphone outputs for any disc at the touch of a button, and Custom Index lets you set and memorize as many as ten index points anywhere on a disc that lacks indexing.

One of the key circuit refinements of the CDP-X55ES is its High-Density Linear Converter (HDLC) system, Sony’s proprietary version of 1-bit digital-to-analog (D/A) conversion, which is being used in many new CD players. Unlike a conventional multibit D/A converter, which re-creates the analog waveform as a series of voltage steps, an HDLC converter transforms the digital signal into an extremely high-frequency stream of constant-amplitude, variable-width pulses. A low-pass filter removes the ultrasonic energy in the pulse train, leaving the reconstructed audio waveform.

Whereas the distortion of a multibit converter usually increases at low signal levels because of nonlinearity and zero-crossing distortion, HDLC and other 1-bit conversion systems are inherently very linear and distortion-free throughout their range. Any 1-bit conversion process results in a higher noise level, however, which Sony reduces by means of noise-shaping technology developed by NTT (Nippon Telegraph and Telephone). The Sony HDLC d/a converter operates at a clock speed of about 45 MHz, some 1,024 times the CD sampling frequency of 44.1 kHz. The converter chip also includes a “direct digital sync” circuit that is said to eliminate “jitter” by accurately synchronizing the master clock with the various stages of the D/A converter.

The CDP-X55ES shares the distinctive and tasteful styling of Sony’s other ES components, with clearly marked, legible control buttons on its black panel and wood-grain-finished side panels. In normal operation, the principal visible controls are the transport buttons and a matrix of buttons numbered from 1 to 20 for direct access to tracks. A small knob adjusts the volume at the headphone jack and the variable-level output jacks on the rear apron, which also has a pair of fixed-level outputs and an optical digital output. A vertical row of play-mode buttons are marked continue (normal operation), shuffle (random-order playback), program (for user-selected track sequencing), and C index for the Custom Index function. A narrow door at the bottom of the panel hinges down to reveal thirteen buttons, most of which operate the player’s special features. Among them is a repeat button that toggles between off and repeating a track, the entire disc, or the programmed sequence.

The disc drawer, which is acoustically sealed to exclude external noise from the disc compartment, opens and closes at the touch of an adjacent button. The display window below it shows track and index numbers and elapsed playing time. It can be switched by one of the Custom File buttons to show the time and number of unplayed tracks remaining on the disc. A music calendar shows the numbers of the unplayed tracks (to a maximum of twenty). The display also provides information about the settings of the special operating features.

The CDP-X55ES is supplied with a wireless remote control that duplicates all of its main front-panel operating controls plus a few of the Custom File controls. It includes buttons that open and close the disc drawer, blank the display or have it show only the current track number

and the music calendar, step through index points, and search slowly or quickly in either direction, vary the volume setting (the front-panel control is motor driven), insert a silent interval between tracks, and repeat any selected portion of the disc (A-B repeat). The remote track-selection number matrix also includes a >20 button that enables you to key in tracks up to No. 99.

The Sony CDP-X55ES measures 18-3/8 inches wide, 14 inches deep, and 4-3/4 inches high. It weighs 27-1/4 pounds. Price: $900.

Lab Tests

Output voltage from a 0-dB recorded test signal was 2.46 volts (fixed or maximum variable level). Frequency response was +0.01,— 0.02 dB from 20 to 20,000 Hz, with channel levels balanced within 0.02 dB. The de-emphasis equalization error was ±0.005 dB from 125 to 16,000 Hz.

Channel separation was about 125 dB from 100 to 1,000 Hz, 121.5 dB at 10,000 Hz, and 116 dB at 20,000 Hz. Total harmonic distortion (THD) plus noise at a 0-dB level was less than —94 dB (0.002 percent) from 20 to 20,000 Hz. Whereas most CD players exhibit greater distortion at high audio frequencies than at low ones, the CDP-X55ES hit its minimum of 0.0015 percent distortion at 20,000 Hz. At 1,000 Hz, the distortion was about 0.0015 percent at all levels below — 10 dB and reached a maximum of 0.0018 percent at 0 dB.

The low-level linearity of the Sony HDLC D/A converters was exceptional. At —70 and —80 dB, the error was a mere —0.3 dB. At —90 dB, it was +0.2 dB, and at — 100 dB it was only +0.1 dB. A spectrum analysis of the CDP-X55ES’s noise output showed it decreasing from — 120 dB at 20,000 Hz to — 140 dB at 300 Hz. At lower frequencies, the average value continued to drop, to about — 145 dB at 30 Hz, with moderate variations around the average. Power-line hum was almost undetectable, — 135 dB or less.

The player’s interchannel phase shift varied only ±0.3 degree from 20 to 20,000 Hz. Its dynamic range (EIAJ) was 99 dB, with wide-band noise (A-weighted) at — 120 dB and quantization noise at —96.4 dB. The frequency (speed) error was — 0.0012 percent.

The CDP-X55ES tracked the 2,000-micrometer calibrated defects of the Pierre Verany #2 test disc with only a single barely audible tick, and it tracked two successive interruptions of 1,500 micrometers without audible errors. Its laser transport was fast, requiring only 1.4 seconds to move from Track 1 to Track 15 of the Philips TS4 test disc. Resistance to physical shock was very good, with no audible mistaking from rather hard knuckle raps or fist blows (a hard slap with an open palm on the top of the cabinet produced only a momentary interruption of the program).

Comments

Our test results leave no doubt that the Sony CDP-X55ES represents the current state of the art in CD players. Virtually every measurement surpassed those of the best players we have tested in the past. Although perhaps a couple of its individual measurements have been matched or slightly exceeded by other units, no other has come so close to overall perfection as the CDP-X55ES. But it would be unreasonable to expect that the superior measured performance obtained from the technical advances embodied in this player would yield better sound than that of other good CD players with normal recordings. Maybe with carefully selected discs and ideal listening conditions, keen-eared listeners could detect some differences. They will have to make their own judgments.

Anyone, however, can appreciate the special features built into the Sony CDP-X55ES. Many of them are not unique to this product, but the total versatility they provide would be hard to match. With the Custom File controls concealed, the player’s appearance is as unthreat-ening as could be desired, but lowering the hinged door reveals its unequaled operating flexibility. Considering all the CDP-X55ES does, and how well it does it, this beautiful product is an excellent value.

Read all

Sony reviews

Read all