Spectrum Purifier and Codename Turquoise II

CD and CD Tray Colorizers


Using Color to Improve CD Player Performance

Copyright 2013 .......Geoff Kait, May 2013

The Green Pen and Beyond

Ever since the introduction of the Green Pen (AudioPrism CD Stoplight) more than twenty years ago there has been considerable debate whether the physical data on the CD solely determines the sound ("1's and 0's"), whether error correction codes correct all errors and whether the sound of a CD can be influenced by color. Machina Dynamica recently introduced two products for colorizing CDs and the CD tray. Both products operate by absorbing background scattered laser light to improve optical performance. During normal CD player operation scattered light in the CD transport compartment has the potential to make its way into the photodetector where it can be "misinterpreted" as real data, producing noise and distortion. In addition to colorizing CDs Machina Dynamica has another product Dark Matter that addresses the invisible portion of scattered laser light, that invisible light being impervious to color.

One of Machina Dynamica's colorizing products is a set of ultra-thin color-coded dots that is applied to the surface of the CD tray. This set of colored dots provides much better scattered light absorption than the stock black plastic tray and better than a matte black painted tray. The other product is a set of permanent ink pens for coloring specific areas of the CD -- in particular, the 1/8 inch wide circular silver track on the data side of the CD located just before the start of the data, as well as the outer and inner edges of the CD. Colors are NOT applied to the clear plastic ring surrounding the spindle hole or the label side of the CD. Both new products can be applied to all types of CD players - including top loaders - AND to all CDs, DVDs and SACDs. We also now offer similar products designed specifically for Blu Ray players and Blu Ray discs -- Codename Top Banana II is a tray masking system for Blu Ray players (when playing Blu Ray discs). When playing CDs, DVDs and SACDs, Blu Ray players employ a red or infrared laser. Thus, when playing non-Blu Ray discs in the Blu Ray player the Turquoise II pattern of colors must be used. Blu Spectrum Purifier is our new Blu Ray disc coloring kit.

CD Laser is Invisible but Appears Red

CD players use a near-infrared laser (wavelength 780 nm), while SACD and DVD players both use a red laser (wavelength 650 nm). While the nominal wavelength of the CD laser is just beyond visible red, it exhibits light in the visible red because the laser is not perfectly monochromatic. Blu Ray players use a 405 nm (blue violet) laser for Blu Ray discs; they use red or infrared lasers when playing CD, DVD or SACD discs. Blue-green and yellow are the complementary colors for red and blue-violet, respectively, which is why the color-coded dots absorb photons of those wavelengths. NOTE 1: The infrared (invisible) portion of the CD laser is not affected by color so scattered light in the infrared spectrum remains unabsorbed. Since DVD and SACD players both employ red lasers, there is no similar issue for those players. NOTE 2: Both Spectrum Purifier and Codename Turquoise II comprise a total of four colors.

How Laser Light is Scattered

CD laser light is scattered when it strikes the edges of the physical data. The scattered light goes off in all directions, filling the CD transport compartment with light. Some of this scattered light makes its way into the photodetector where it can be detected as real signal. The photodetector is designed to be insensitive to light with power below a certain threshold (around 75% of the full reflected power of the laser); however, much of the scattered laser light exceeds that threshold and can therefore potentially be detected as real signal by the photodetector. The photodetector detects the differences in power between the direct reflected light and the absence of light as the laser beam navigates the spiral of physical data. The photodetector, like the laser, is not Absolutely Monochromatic and can detect photons having wavelengths other than 780 nm.

Reed Solomon error correction routines that reside in the CD player are not particularly effective correcting random errors like those produced by background scattered light; the Reed Solomon codes were implemented by CD player manufacturers to correct non-random errors such as those caused by fingerprints and scratches. Optical performance of CD players can be improved by adding certain color(s) that reduce the amount of background scattered light entering the photodetector. When the colors are placed in close proximity to where the laser is reading the data - i.e., where the scattering is ocurrring initially - the effectiveness of the colors is optimized.

For Blu Ray players, Top Banana II should be used for Blu Ray discs only - Turquoise II should be used for all other formats in Blu Ray players since different color lasers are used for different formats - blue-violet for Blu Ray, red for DVDs and SACDs and infrared for CDs. The color-coded dots used in Turquoise II and Top Banana II are ultra thin and will not interfere with the CD player's or Blu Ray player's operation.

Hearing Colors

How does coloring the CD and CD player tray affect the sound? Spectrum Purifier and Codename Turquoise II improve the sound of any CD and make it more dynamic, more detailed, more focused, less distorted and more correct-sounding. If you treat the CD in other ways, e.g., demagnetization, optical enhancement fluids, etc., colorizing the disc and tray will further improve the sound of the CD. The colored CD and CD tray produce a larger, more expansive soundstage, better pitch control and better channel separation.

How the Laser Reads Data on the CD

Diagram 1 - CD Laser Reads Bumps (Pits Inverted) and Lands,
both of which have reflective metal surfaces. The photodetector
receives no signal from bumps, only from lands, due to destructive
interference of light waves. See last paragraph below.

Pits and Lands come in 9 different lengths, from T3 to T11.

T3 = 10001
T4 = 100001
T5 = 1000001
T6 = 10000001
T7 = 100000001
T8 = 1000000001
T9 = 10000000001
T10 = 100000000001
T11 = 1000000000001

The CD laser reads the pits as if they were "bumps." Pits are depressions when viewed from the label side. The bumps and lands are completely reflective and reflect the full laser signal to the photodetector. But due to the geometry of the pits/bumps the photodetector receives no laser signal from bumps. See paragraph below. So data on the disc is read as a series of ON and OFF signals of varying lengths that represent the digital information.

Things that go Bump in the Night - Why Bumps Don't Reflect Laser Light

The typical CD laser has a wavelength in air of 780 nm. The wavelength inside the polycarbonate is a factor of n=1.55 shorter (about 500 nm). The pits are designed to be 1/4 wavelength deep. Thus, for a bump and a land, the difference in the distance light travels from the laser to the photodetector is 1/2 of a wavelength. So the light reflected from the bump is exactly out of phase with the light reflected from the land, so the two light waves cancel each other - i.e., the bumps all look dark to the photodetector. The laser beam is slightly wider than the width of a bump in order for the beam to reflect off the bump and land simultaneously.

Diagram 2 - Destructive Interference of Light Waves. The destructive interference
of light waves reflected by the bump and land occurs due to the depth of the pits
being precisely 1/4 wavelength of the laser - thus, the distance the laser beam travels
from laser to photodetector is 1/2 wavelength longer for lands than for bumps.
The laser beamwidth is slightly wider than a bump so it always illuminates the
adjacent land whenever it illuminates a bump; consequently, bumps always appear
dark to the photodetector due to destructive interference of the light waves.