Akai CD-93B CD-player Review

At first glance Akai’s Reference Master CD-93B, which heads the company’s current line of CD players, looks much like many other full-featured players, but it has a number of advanced circuit and construction features. Some of the latter can be appreciated when you pick it up— the CD-93B weighs a solid 30 pounds, more than twice as much as most full-size CD players!

Akai’s engineers designed the CD-93B to avoid three weaknesses that they had concluded were shared by most current CD players: nonlinearity in the digital-to-analog (D/A) conversion process, vibration in the laser tracking assembly, and internal signal degradation through interference and signal loss. Their solution to the first problem was to use true 18-bit digital filters with quadruple oversampling. A major benefit of this feature is to maintain linearity down to the lowest signal levels, where most CD players have substantial amplitude errors. Also, the high sampling frequency (176.4 kHz) effectively eliminates switching products from the analog output without requiring the use of high-order analog low-pass filtering. Since separate d/a converters are used for the two channels, interchannel phase shift is also essentially absent.

Internal signal degradation has been minimized by the use of optical couplers and fiber-optic cables to carry the digital signals within the player, isolated power supplies with separate power transformers for the analog and digital circuitry, and separate transformer windings and regulated supplies for the left and right analog channels. The digital circuit boards are also shielded to prevent their signals from leaking into the analog portions of the player.

The reduction of vibration transmission was achieved by the player’s massive, rigid mechanical construction. The chassis is formed from a single U-shaped piece of die-cast aluminum molded with a raised honeycomb surface. The top plate of the chassis is a piece of 3.2-millimeter-thick (about 1/8 inch) copper-plated aluminum. Even the disc drawer, typically a molded plastic assembly in other CD players, is a single, rigid piece of die-cast aluminum, and there is a large aluminum clamp for damping disc vibrations during play. For more rapid track changes and cueing, a linear motor is used to drive the laser.

The Akai CD-93B has a full complement of control features, including programming for playback of up to twenty tracks in any desired order and direct access to any track or indexed section. It has the usual repeat functions, auto-spacing (a 4-second pause between tracks during playback), and a very complete display window, including a “Music Calendar” that shows the playing and programming status of all the tracks on the disc. Another part of the display shows the current track and index numbers, the operating mode, and elapsed or remaining time in both the current track and the entire disc. A button can switch off the entire display except for the current track number and the operating-status indication.

The front panel of the CD-93B has a headphone jack with its own volume-control knob. The player can be set up for external-timer operation with a switch below the disc drawer. The rear apron has gold-plated phono-jack outputs for the analog line signals and a coaxial output for the digital signals. There is also an optical digital output connector and a switch that turns the digital outputs on and off.

The CD-93B comes with a wireless remote control that duplicates all of its front-panel controls except the power switch, headphone volume control, and timer switch. The player is finished in black with pale gold markings. It measures 18 inches wide, including the wood-grain side panels, 13 inches deep, and 4-1/2 inches high. Price: $1,199.

Lab Tests

The frequency response of the Akai CD-93B was one of the flattest we have measured, varying only + 0.1, —0.05 dB from 20 to 20,000 Hz. The two channels had identical responses, and their levels differed by only 0.02 dB. The output from a 0-dB 1,000-Hz test track was 2.06 volts into an EIA standard load. The headphone volume was good with medium-impedance phones.

The 1,000-Hz harmonic distortion (excluding noise) was 0.0033 percent at 0 dB, 0.0057 percent at —10 dB, and 0.0128 percent at —20 dB. The A-weighted noise level was — 104.5 dB referred to a 0-dB level, and the dynamic range was 100 dB. The channel separation was symmetrical (measuring the same from left to right as from right to left): 90 dB at low and middle frequencies, 66 dB at 20,000 Hz.

The low-level linearity (with dither) of the player’s output, measured with the CBS CD-1 test disc, was the best we have found so far, with maximum errors of less than 0.3 dB down to the — 100-dB level. The interchannel phase shift was nearly unmeasurable, typically less than 1 degree and reaching 2 degrees at 20,000 Hz. As with most CD players, the 100-hz phase shift was about 4 degrees, also entirely negligible.

It came as no surprise, considering the construction of the Akai CD-93B, to find that it had no difficulty whatever in tracking all of the calibrated defects on the Philips TS5A test disc and that its playback was unaffected by anything less violent than a fist-slamming blow to the top cover, over the disc—which hurt me more than it did the player! The laser slewing was fast and accurate, with typical track-to-track times of about a second or less.

Comments

Our test results on the Akai CD-93B speak for themselves. It is truly a top-rank player, and its performance and features are commensurate with that status and with its price. We did not have an opportunity to use its digital outputs with an external d/a converter, although it is difficult to imagine any improvement that could result from such operation (when we have made such comparisons in the past, the results have not been as good as with the players’ own converters).

In any case, this handsome product lived up to our expectations in full measure. So far as we could tell, it did not sound any different from other good CD players, but the benefits of this type of attention to detail rarely, if ever, translate directly into improvements in sound quality. They are real nonetheless and frequently well worth a premium cost.

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