Adcom GCD-575 CD-player Review

Adcom’s GCD-575 CD player combines simple, easy-to-operate controls with several advanced circuit-design features that set it apart from other players. Despite its considerable operating versatility, it presents a neat, uncluttered appearance with a semi-gloss black finish (it is also available in white), small round pushbuttons, and exceptionally legible white markings.

The GCD-575 uses dual digital-to-analog (D/A) converters, quadruple oversampling, and low-group-delay digital and analog filters. Its analog audio section is direct-coupled and has a low, 100-ohm output impedance, which permits the player to be used with almost any type of amplifier or preamplifier with minimal signal degradation even when there are long connecting cables.

In addition to its two analog audio outputs, the GCD-575 has a coaxial digital output for use with an external d/a converter. One analog output provides a fixed level (nominally 2.5 volts), and the level from the other, up to a maximum of more than 4.5 volts, is controlled by a front-panel knob. Providing this combination of low impedance and high output level actually requires a small built-in power amplifier, in contrast to the low-level amplifier output stage of a typical CD player, and Adcom has designed a high-quality Class A amplifier for that purpose. The variable output can drive a system power amplifier directly, eliminating the preamplifier, or it can be used for headphone listening through the front-panel jack. A multiwound power transformer and three separate regulated power supplies operate the audio, digital, and display circuits and isolate them from each other.

The GCD-575 has all of the conventional CD player operating controls, including track skipping and fast search (with sound) in either direction and a repeat function for the entire disc or a selected portion. An Intro feature plays the first few seconds of each track before proceeding to the next one (the play time can be set from 1 to 60 seconds using the player’s remote control), and Auto Space introduces 4 seconds of silence between tracks. The memory button is used for programming a sequence of up to twenty-four tracks in any order.

Two unique features of the GCD-575 are its polarity switch and its Analog Frequency/Phase Contour (AFPC) circuit. Normally, in accord with CD recording standards, the polarity of the player’s output signal is positive. Pressing the polarity button simply inverts the signal’s polarity (and the small red led in the button changes from red to green). It has been claimed that the sound from some recordings can be improved by a polarity reversal, and this control makes it easy for the user to decide for himself. The AFPC feature is a proprietary Ad-com circuit that is designed to make overly bright CD’s sound more like good analog discs. Activating it lights a red led in the AFPC control button.

The display window contains a twenty-selection Music Calendar that shows the numbers of the unplayed tracks on a disc. Initially, the total number of tracks and total playing time are displayed. During play, the current track number and its elapsed playing time are shown. The time button toggles between elapsed time in the track, elapsed time on the disc, remaining time in the track, and remaining time on the disc. Illuminated words appear as required to identify the status of the player’s other functions.

The GCD-575 comes with a wireless remote control that duplicates almost all of its front-panel controls and provides a ten-key numerical keypad for direct track access. The player can also be operated from an external timer. The memory system is unusual in that pauses can be placed in the program wherever desired (play must be pressed to resume the programmed sequence). Also unusual is that the player can be programmed with the disc drawer open, allowing reference to the disc label when making selections.

The Adcom GCD-575 measures 17 inches wide, 11-1/4 inches deep, and 3-1/2 inches high. It weighs 12 pounds. It comes with a high-quality 4-foot interconnect cable with gold-plated plugs. Price: $600 ($650 in white).

Lab Tests

The output of the Adcom GCD-575 was 2.65 volts from the fixed-level jacks and a maximum of 5.8 volts from the variable jacks. The channel imbalance was a barely detectable 0.02 dB. The frequency response was flat within +0.05, — 0.025 dB from 10 to 20,000 Hz. With the AFPC circuit active, the portion of the frequency range below 1,000 Hz was boosted by about 1 dB, and the response rolled off above 1,000 Hz to —2.5 dB at 7,000 Hz and —3.2 dB at 20,000 Hz.

The interchannel phase shift was the lowest we have measured from a CD player, less than 0.2 degree overall from 5,000 to 20,000 Hz. The AFPC circuit had virtually no effect on phase shift, which differed from the normal measurements by a maximum of 0.4 degree in the 6,000- to 8,000-Hz range.

The channel separation measured 101 to 109 dB at 1,000 Hz, falling to 76 dB at 20,000 Hz. Harmonic distortion at a 0-dB level was nearly constant over most of the audio range, reading 0.0028 percent from 20 to 1,000 Hz and reaching a maximum of 0.011 percent at 12,000 Hz. The 1,000-Hz distortion was 0.0028 percent at 0 dB, 0.0022 percent at — 30 dB, and less than 0.002 percent from — 50 to — 90 dB.

The low-level linearity of the GCD-575 was the best we have yet measured, with no measurable error (which means less than a fraction of a decibel) down to our — 90-dB measurement limit. The A-weighted noise level was — 109 dB referred to a 0-dB signal level, and the dynamic range was 95 dB. Power-line hum (60, 120, and 180 Hz) was between -115 and -130 dB.

Continents

Our measurements established that the Adcom GCD-575 is a superlative CD player, surpassing any other we have measured in respect to phase shift and linearity over the full recorded dynamic range and in general pushing the state of the art in digital-disc playback. The numbers speak for themselves, and even if it has not been clearly demonstrated that this degree of refinement has audible benefits, our measurements show that the GCD-575 was designed and built with an extraordinary attention to detail.

The player had no trouble in tracking the largest calibrated defects on our Philips test disc, and its slew time of 2 to 2.5 seconds, while not one of the shortest available, should be fast enough to suit most people. Frankly, in view of the near perfection of its disc-playing performance, we were a little surprised to find that it was not totally immune to physical shock: A moderate tap on its top was able to induce a dropout (although this effect was minimized if the player was on a very firm, rigid support). We doubt, however, that anyone would find this vulnerability to shock bothersome.

When we experimented with the polarity-inverting and frequency-contouring features, there were no surprises. Except for the change in the color of the led indicator, we detected no change in any program when the output polarity was inverted. Of course, even the most “golden-eared” listener rarely, if ever, hears any differences between one polarity and the other. The AFPC circuit is another matter. When the program had appreciable high-frequency content, there was a definite softening effect when the contouring was used. When we played one of those hard-sounding discs that gave the CD a bad name in its early years, the circuit made a worthwhile improvement. With any reasonably good recording, however, the unmodified playback is likely to sound just as good (but not identical).

The quality of the Adcom GCD-575 was also apparent in the design of its operating controls. As with any equipment of equivalent complexity, its instruction manual should be studied carefully in order to appreciate its special qualities. But after that, one could hardly wish for a simpler or more versatile CD player. If the GCD-575 had been as impervious to our pounding on its cabinet as a couple of other players we have tested in the past, we would have been sorely tempted to call it “the best” in the field—and that’s a verdict we rarely render.

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