As We See It

Editor: Upon receiving the critique by John Atkinson, a laboratory examination of the specific compact disc in question was made by Lou Dorren. Lou's comments are as follows:

1) The original PCM-1 digital master is clean, with no distortion as described by JA.

2) When the PCM-1 to Colossus transfer was made, the digital medium was truly exercised with regard to program level.

3) This push of the medium may cause the kinds of distortions referred to by JA. The levels on this disc were recorded within 8 bits [LSBs] (hexadecimal notation FFF4) of the maximum level for a 16-bit system (hexadecimal notation FFFF). Any offset error in the D-to-A converter or the sample-and-hold system of the CD players that exceeds the 8-bit margin (hexadecimal notation 0008) will cause the distortion described, due to nonsymmetrical playback of the reconstructed audio signal.

4) The assumption made during mastering was that CD player manufacturers were adhering to the EIAJ standard. Apparently some are not following the standard to the full 16-bit dynamic range of the system.

5) This disc in its current configuration will certainly verify the offset accuracy of one's own CD player. We have one player in the lab now that will not play this CD at all.

6) As a consequence, a new master transfer will have been prepared on April 4, 1988, in which the level was reduced by 3dB (hexadecimal notation F800). This translates to a 2048-bit margin (hexadecimal notation 0800) instead of an 8-bit margin. Any owner of this CD who would like to trade it for a remastered version may do so at no charge. However, one should consider the retention of the disc as a test medium for one's own edification, being certain to mark this particular disc for identification.—Brad Miller, Lou Dorren, Mobile Fidelity Productions of Nevada