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It must be clear by now that the timely detection of a pit transition resulting in a digital 1 is a matter of critical scrutiny. Even the smallest deviation in detecting the precise transition results in timing errors called jitter. Causes of jitter are many. It could be bad pressings where the pit walls aren’t perpendicular to the surface but crooked. Other optical problems prevent the laser beam to properly hit the reflective layer with the pit pattern through the polycarbonate. This could arise when a CD is still greasy from the stamping process. Other optical problems are the result of light scattering in the plastic layer rather than getting a clear lock. Wobbly or eccentric discs are also detrimental to correct data capture as the laser needs to physically adjust hundreds of times a minute to track the erratically spiraling pits. Poor power supply design compromises matters further as the laser’s motor power is diverted by other circuits. The large currents of the laser servo (which assists in tracking the pits) can interfere with the tiny response current in the optical read diodes. And so forth.

The upshot simply is utter confidence that calling the audio CD a mostly analog medium is correct. By the way, a data CD for computer use is truly digital by design. It operates with different error correction schemes and sports no spiral groove but is addressable directly to any given word and capable of re-reading certain sectors as needed. Is it any surprise then that the audio market is overrun by ‘after-market’ tools meant to adjust or correct the quality of audio CD data read-in?

Analog CD tweaks, a necessity in an imperfect world
: We’ll list merely a few examples to drive home the point that CD is mostly analog by nature. Green markers color the edges of a disc to prevent stray light exiting the disc through its side where it can interfere with the laser’s focus on the actual data. Circumcision/beveling of the outer edge again counters stray light issues. Then there are mats made from plastic, carbon, graphite or even Corian aimed at stabilizing a CD and/or to increase its reflective properties. Various cleaning products champion clean surfaces. Then there’s Nespa "light therapy" where high-intensity photon bombardment alters the polycarbonate’s molecular structure (or eliminates gas pockets) to improve the sound. Then there are the various demagnetizing and anti-static treatments. All have audible effects. The issue is not whether those effects are positive or negative. The issue is their audibility. If 1s and 0s were just 1s and 0s, none of these addresses should make any difference whatsoever. Yet as we well know, they do.

Even playing a CD twice in a row changes things since the second time static charges have built up. We’ve often ripped a CD with EAC to make a copy and burn that at the slowest speed on an excellent MAME Gold CDR blank. While time consuming, the improvements can’t be argued with. In short, a CD has so many analog aspects to it that calling the medium digital is a profound error in our opinion. Perpetrating it invites grave misunderstandings which are epitomized in the throwaway line “it’s just ones and zeros”. Far from it.

The second digital revolution begins:
Why such a comprehensive introduction? PS Audio has introduced a device which completely eradicates the analog aspects of a CD from interfering with playback. This device is called the Perfect Wave Transport or PWT for short. It’s an optical disk reader which reads WAV audio files from both CD and DVD including HRx. That in itself is nothing new. What’s new is the fact that these read-in data are stored in a 64MB memory bank.

Data capture doesn’t occur via a fancy high-end drive like a Philips CD-PRO2 or Esoteric VRDS sled. Read-in occurs via optical ROM reader of the same lowly type you encounter in your computer. Yet the PWT is no computer. It is a pure dedicated audio device created by a purely audio-driven company. Whenever a CD or DVD—-for example a 24-bit/176.4 kHz WAV recording by HRX Reference Recordings—is placed in the drawer, the disc is read in ‘bit-perfect ' exactly as a superior software ripper like EAC would. Whenever errors are encountered, PS Audio’s chosen software re-reads the disc as many times as necessary. Once accepted as correctly captured, the data is moved to the PWT's Digital Lens, a jitter eliminator equipped with a 64MB memory which collects raw music information only, i.e. without any embedded clock data.

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