Recording of November 1988: Pierre Verany Digital Test CD
There are two interrelated parameters which, in the absence of drop-outs or information gapswe'll get to them shortlycan affect the ability of a player to track the CD "groove" (or "whorl," as the quaintly translated disc booklet calls it): linear "cutting velocity" and track pitch. The standards for the first establish a range of 1.2 to 1.4 meters/second (the rotation speed of the disc varies from 500 to 200rpm from the inside to the outside of the disc to maintain this linear velocity); for the second, the spacing between adjacent tracks, from 1.50 to 1.70 micrometers (µm).
Manufacturers adjust these on a given disc to accommodate the required playing time; those rare 70+-minute discs use the slowest velocity (1.2m/s) and smallest "groove" spacing (1.50µm). Several tracks are provided on these test discs with various combinations of these parameters. In addition, 25 tracks are recorded with a wide range of dropouts to check for a player's error-correction capabilities. Many of the dropout tests are in excess of the CD Standard but still within the system's theoretical error-correction capabilities. None of the tracking tests require instruments, although a number of other bands on Digital Test do.
I ran six players through these error-correction and tracking tests: the Meridian Pro 207, Marantz CD-94, Mod Squad Prism, California Audio Labs Aria Revised and Tempest II, and Audio Concepts/MSB Silver. All of the players sailed through the cutting velocity/track pitch tests. The dropout tests were another matter. All passed up to and beyond the required standard, but ran into various degrees of difficulty beyond that. None passed all of the test bands.
Interpreting the results required a degree of judgment; in the ratings I have subjectively balanced passes, failures, and marginals (where a player mistracked at the very start of a band but stabilized after a second or two). I don't intend to go into all of the details here; suffice it to say that the Aria ranked best, followed closely by the Prism and the Tempest II. In practice, I have never encountered any tracking glitches from any of these three machines, and consider them practically equivalent and fully satisfactory in their tracking and error-correction abilities. The MSB measured in the same league; but in practice it has shown a (rare) tendency to mistrack with a loud, static-like snapping. The 207 and CD-94 were both dramatically worse in their measured ability to correct for dropouts. Both players met and even slightly exceeded the standard; yet both failed to correct for 1.5mm and larger dropouts (the other players, in contrast, corrected single dropouts of 2.5mm). Both were unable to correct anything beyond a 1.0mm dropout at the minimum (1.5 micrometer) track pitch; the other four players corrected up to 2.4mm dropouts at this same pitch.
The bottom line? None of the six players, in actual use, mistracked enough to be rated unsatisfactory. But, as stated in the 207 review, you can anticipate that the Meridian (and the Marantz) will be much more sensitive to disc flaws and, especially, disc damage. As to the possible effects of dropouts on the sound quality of these machines at a pre-mistracking level, the jury is still out. The poorest of them sonically, the CD-94, was a mediocre tracker. But so was the Meridian, one of the best-sounding.
One other unusual test on these recordings is worth mentioning. Two bands permit a listening evaluation of the functioning of a player's de-emphasis circuits. A musical selection is recorded with and without pre-emphasis (a kind of "equalization" analogous to LP equalization but not used in most CDs; see the 207 review for more on this). If the two sound the same, the player de-emphasis is functioning properly; all of these players passed.
This test disc is readily available to the general public (I saw it in a Tower Records in Los Angeles) at a reasonable priceroughly the same as two ordinary CDs. You could, conceivably, bring it along on your CD-player shopping safari. But be careful. A number of the bands are potentially hazardous to equipment (there are warnings in the booklet). Using only the relatively harmless tracking and correction bands will likely cause your dealer's face to turn interesting shades of amber; blowing the woofers of his favorite demo speakers across the room will not be nearly as much fun.Thomas J. Norton