NAD 5170 CD Changer Review

The Model 5170, one of NAD’s Monitor Series components, is a full-featured CD player that includes a six-disc magazine-type changer for extended automatic playing. Since the magazine loader in the NAD 5170 supplements the usual singledisc drawer rather than replacing it, the user has a choice of either single-or multiple-disc play without having to load a single disc into a magazine. In automatic (changer) operation, all seven discs are accessible, and the playback can be programmed to include any or all of them. According to NAD, the six-disc magazines used in JVC and Toshiba changers are compatible with the Model 5170.

The basic playback system of the NAD 5170 includes a quadruple-oversampling 16-bit digital filter, multiplexed between the channels, along with mild (four-pole) analog filtering to remove the higher ultrasonic frequencies from the audio outputs. The “most significant bit” of each player’s digital-to-analog (d/a) converter circuit is individually trimmed at the factory to minimize distortion resulting from errors in that part of the D/A conversion process. Like amplifier crossover distortion, such conversion distortion becomes more serious as signal levels decrease.

The NAD 5170 is the first home multidisc CD player that includes a switchable dynamic compressor to reduce the dynamic range of compact discs for recording CD’s onto cassettes for playback in a car or simply for adapting an uncomfortably wide recorded dynamic range to a home listening environment. Called the Controlled Dynamic Range (CDR) circuit, the compressor increases the level of soft passages while leaving the highest-level signals unaltered. The resulting program falls within a dynamic range of about 70 dB (which can be accommodated by a good cassette recorder) without any change in its distortion levels or frequency response.

Like most home CD players, the NAD 5170 has extensive programming capabilities. It can be programmed to play up to thirty-two tracks from all seven discs in any order and to repeat any one disc, all seven discs, or a programmed sequence indefinitely. The Model 5170 comes on automatically in the play mode when power is supplied, a convenience when using it with an external timer.

The player’s gray panel (which matches other NAD components) contains a number of round pushbuttons and one knob control for adjusting headphone volume. The open/close button operates the sin-gle-disc drawer, and the eject button affects only the magazine, which loads just above the drawer. There is no stop control, but the reset button performs that function.

The display window, in which all information appears in red against a black background, shows the number of the disc currently loaded. The current track number and its elapsed playing time are the default indications. Pressing the display button below the window changes the readout to the number of tracks remaining and the remaining time on the disc. A row of symbolic discs across the bottom of the window shows which magazine slots are occupied; a triangle appears over the one in playing position.

The operation of the CDR circuit is indicated by a yellow bar at the right side of the display. Below this bar are three buttons used to program the player. Track selection from the front panel requires multiple operations of a skip button.

The NAD 5170 is supplied with a wireless remote control that duplicates almost all of its front-panel controls and has a few additional functions. It has numbered buttons that allow direct access to any track or any loaded disc, an intro scan button that plays the first 15 seconds of every track on a disc, and a random button that plays all the tracks on a disc in a random order. Two volume buttons control the output from the pair of variable-level jacks on the rear of the player.

In addition to the fixed- and variable-level analog output jacks, the Model 5170 has a coaxial digital output jack for use with an external d/a converter. The player’s dimensions are 17-1/8 inches wide, 14-1/2 inches deep, and 4-1/4 inches high. It weighs 13-1/2 pounds. Price: $748.

Lab Tests

The output level from the NAD 5170 is rated at 1.5 volts, less than the CD standard of 2 volts. It measured 1.59 volts, with a channel imbalance of only 0.05 dB. The fixed-level and maximum variable-level outputs were identical. The frequency response was +0.15, — 0 dB from 20 to 20,000 Hz. The CDR compression system reduced the 90-dB range of one of our test discs to a more manageable 72 dB.

The total harmonic distortion (THD), excluding noise, measured 0.01 percent at 0 dB, increasing to 0.016 percent at —20 dB. With noise included, the readings were slightly higher, 0.0115 and 0.032 percent, respectively. The A-weighted signal-to-noise ratio was 100 dB, and the dynamic range was 91.5 dB. In channel-separation measurements we found the left channel reading between 89 and 93 dB from 100 to 20.000 Hz and the right channel slightly exceeding 100 dB at 100 and 1.000 Hz, falling to 85 or 86 dB at 10.000 and 20,000 Hz.

In spite of the factory trimming of the d/a converter, its low-level linearity was not particularly good. From an error of less than 1 dB at — 70 dB, and no measurable error at higher levels, the output error reading increased to 4.2 dB at —80 dB and 7.8 dB at —100 dB. Although these errors may not correlate with any audible qualities of the player, they are surprising in view of the special precautions claimed by the manufacturer. Interchannel phase shift increased linearly from less than 1 degree at 500 Hz to 25 degrees at 20,000 Hz.

The cueing accuracy of the Model 5170 was good, and its slewing time of 1.8 seconds (in our standard but unofficial test) compared well with most of today’s high-quality CD players. When a disc change was involved, the cueing time averaged about 8 seconds, which is at least as good as we have measured from other magazine-loading CD changers. The player’s resistance to impact on its sides was excellent, and it earned a good rating against top-cover impact.

The NAD 5170 had no difficulty tracking through the largest surface defects (black dots) on the Philips TS5A test disc, but the information-layer defects caused mistracking, with accompanying audible ticks and pops, at amplitudes exceeding 600 micrometers.

Comments

In our tests, the NAD 5170 proved itself to be a very good performer, with measurements typically ranging from excellent to good. The major weaknesses disclosed by our measurements were a higher-than-normal susceptibility to information-layer damage on a CD— although we never encountered a tracking problem playing music discs, just with the Philips test disc—and a higher-than-expected linearity error at output levels below — 70 dB.

The player’s front-panel controls appear, at first glance, to be quite different from those of the majority of CD players, but they are actually almost identical in their functions. Our only complaint concerns the programming operation, which works well enough but is unlike any other we have seen. It took some study of the manual, and some practice, to program it with confidence. We also missed the ability to access indexed points on a disc, which we would expect to find in a player at this price level. A very minor point of criticism is the lower-than-standard output level. This was one of the very few CD players out of the many we have tested over the years to fall so far short (and obviously by design) of the industry standard of 2 volts.

On the other hand, the CDR circuit worked very well. Since it does not affect the higher program levels, the immediate effect of switching it on is a pronounced increase in average volume level as the softer portions of the program are raised toward the peak output level of the system. Much of the time we preferred listening with the CDR in operation, since the jarring effects of a sudden crescendo are considerably eased by its action. We also used it part of the time with its digital output driving the d/a converters of an integrated amplifier equipped to process digital signals.

All in all, the NAD 5170 is an exceptionally versatile and functional CD player, combining all the advantages of magazine and singledisc loading in a very attractive package.

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