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What IsThe Real Story About Compact Discs?  My View Of This Recording Medium


The recording industry's promise that CDs were going to be perfect was a myth. I was quite disappointed when I first auditioned them. The sound quality was often harsh or dark, sonic imaging and staging was almost non existent, and their dynamic ranges sounded way off.  I didn’t think that the sound presentation was at all representative of the recordings, and I didn’t think that the digital compact disk would ever surpass analog records.

My perspective shifted when I first heard CD reproduction that showed promise. It was at the 1991 Winter CES.  Harmon Kardon was showing their latest top of the line CD player.  The unit sounded excellent, and it was well constructed and engineered. It featured fully discrete-transistor audio circuitry, two regulated power supplies, and the latest digital chips by Burr Brown.  I was intrigued by this particular digital technology and desired to hear one of their players in my system.

A few months later I purchased the Harmon Kardon, HD7600 and began to do serious listening tests with it. This was new territory for me, because until then I had only used analog records for my signal source. This was the beginning of my quest to achieve the highest possible performance from the compact disc, and I speak only of the standard Red Book CD, not of the SACD or HDCD formats that followed it.

My work targeted three major areas: 1) designing modifications that would improve CD players, 2) designing a line level preamplifier dedicated to CD reproduction that would optimally process the player's analog signal, and 3) designing modifications that would improve the compact disc itself.  The Harmon Kardon HD7600 proved to be a very good choice for these tasks.

Improving The Player

I started by modifying its power supplies, re-designing their current paths by individually isolating them and adding multistage DC filtering. By creating isolated current paths between individual digital processing chips and individual audio stages, I was able to significantly lower distortion and create a more enjoyable listening experience.  Signal hash and noise were reduced, and instrument timber and body were more defined.  This was a great design achievement, and it led me to continually explore CD player power supply development.

I next experimented with critically damping and tuning the player's mechanical structures.  By damping out vibration in the transport, the loading tray, and the frame, I achieved major sonic improvement.  These modifications required careful application because, if I over-damped any part of the player, it took the life out of the sound.  I did a lot of testing in order to find the right damping combinations and material combinations.  Continued tuning and listening were crucial for success, and I was careful to log any changes that I made.  This ended up being a very complex process because everything I tried had an affect – even something as small as the torque of a screw made a significant sonic difference.

When the modifications reached a plateau, I began testing products designed to isolate the CD player from vibrational feedback.  I tested spring bases, sonic absorbers, a platform base by a company called Micro Scan, and several isolation platforms created by a company called Machina Dynamica.  I found that they all offered some benefit, but that a well-engineered isolation platform provided the most.  I successfully used Micro-Scan's CD platform for many years, then I moved up to Machina Dynamica's decoupled air-spring platform.  The sonic improvements were monumental.

Creating An Optimal Preamplifier

My curiosity and thinking had been piqued in the early 1990s when I noticed that many designers were attempting to achieve good sound from CD players by running them through spatially colored and warmly voiced vacuum-tube preamplifiers.  When I listened at audio shows, I was convinced that many of the preamplifiers being displayed were unable to track the highly dynamic signal that was coming from the system’s CD player.  I believed that the preamplifiers were degrading the sound by adding harmonic distortions to the source signal. Up until the introduction of the CD player, everybody had been designing preamplifiers that processed signals produced by analog record players.  Designers were now dealing with a new type of animal, and it was clear to me that CD players posed quite different challenges.  One could not tame the sound by slowing it down with tricks like adding time and phase distortions.  I knew my direction, and my task now was to develop an optimal preamplifier for CD reproduction.

At this point I had been designing and re-engineering preamplifiers for 15 years, and I had developed excellent phono preamplifiers with low noise and low distortion. So, for the first tests, I listened to my player through the line section of my best phono-preamplifier.  The sound was too strident and sharp because I had too much signal level to deal with, and because the audio signal was being processed by so many solid state devices.  Since the innate transparency of the preamplifier was showing the inconsistencies in my CD player, I went to work designing a preamplifier that could track the extended dynamic range of the CD signal and handle its high voltage levels, while at the same time adding body to the sound, making it more palpable.

The result: I created a low-gain vacuum tube preamplifier that incorporates very high speed vacuum tubes with ultra low-distortion signal input pads.  The preamp is designed to create body in the sound presentation by tailoring the audio signal at its frequency extremes.  When this is carefully done, it doesn’t audibly distort the sound.   This design has taken years to perfect, and it is still undergoing subtle improvements that keep it current with the improvements being made in digital-to-analog converters.

Refining The Software

Through all of this work, I was also learning how to successfully modify the CDs themselves.  Beginning with their introduction, the high-end audio industry was in full swing creating tweaks that claimed to make the sound from CDs better.   There were optical sprays, balancing rings, edge treatments, player lens modifications, and player transport modifications.   When I listened to them, I could hear that many of them altered the sound, so I sought to find out which ones truly improved it and which ones degraded it.

I started by testing a centrifugal balancing ring designed by Sim-Audio.  I had seen the product demonstrated, and it effectively reduced wobble in the spinning CD. This gave the laser pickup a more stable target to hit, and reduced the servo action of the lens.  Adding the balance ring produced several noticeable improvements; the audio signal had lower harmonic and inter-modulation distortions, the sound was presented with a blacker background, and the audio signal exhibited lower levels of high end hash.  This was a keeper!

One of the most profound demonstrations that I have ever heard at CES was from a company which had done research on how to block light re-fraction and light re-transmission from the edges of the CD.  They were convinced that light scatter was a problem for CD players because it distorted the data- reading process.

When the red light emitted from the laser strikes the reflective surface of a CD, it both creates a pin-point reflected signal and lights up the CD's clear polycarbonate base material.  This refracted light then gets re-transmitted out of the inner and outer edges of the CD as a delayed signal.  And, if this delayed signal mixes back into the laser pick up, it creates errors.

Their product was a green colored edge coating called CD Stop Light.  The color was an opaque green, because they had calculated that this color most effectively blocked and absorbed red laser light.  I was very excited when I heard the controlled comparison of a CD with the edge treatment and one without.   The CD with the edge treatment produced a much clearer audio signal.   The most noticeable improvement was the appearance of very low-level detail in the sound stage.  Magically, it just showed up.  I heard greater depth of image, better back round clarity, and better individual instrument and voice definition. Finding this edge treatment was a major step forward, and I was eager to test it out for myself.

Trusting my sensory perceptions has always moved my design work forward, and most, if not all, of my discoveries about improving CDs have come from doing evaluation through qualitative testing.  My processes for evaluating CDs fully came alive when I first worked with the CD Stop Light.  Comparing this product with material that I knew well gave me a new basis for evaluation.  Its sonic improvements were even greater than those I experienced at the CES.  I could hear many new fine musical details, and my CD listening was far more enjoyable.

However, after extensive use of the product, there were two things about it that I did not like.   With it, the sound of my CDs became cooler.  In addition, the product was also difficult to apply and remove.  So, as an alternative to the CD Stop Light, I began to investigate the application of green magic markers to the edges.  I performed extensive testing with it, and I was very pleased with the results.  The application of the green ink provided similar improvements in definition, but the overall sound did not get cooler.   Moreover, the ink was easily removed with alcohol, making repeated testing easier.

Finding these edge treatments, was a major step forward in the modification of discs because this was the catalyst that led me to experiment with color.  When I was discussing the green ink application with a good friend, he suggested that I do testing with an additional color.  I chose red because it was the same color as the laser light, and I was interested in its effect as a color filter.  It also enhanced the CD, but in a very different way than the green.  It added bass, much like a tone control in a preamp does, and it also smoothed out the hi frequencies.  So at this juncture in my testing, I was experimenting with both green and red inks.  I had the choice of applying one or the other to the outer edge of a CD, and one or both to the inner clear circle at the center.  The combinations proved to be quite tonally different, and the two colors gave me a very powerful set of tools.  With them, I was able to achieve a more accurate and pleasing sound: better bass clarity, higher resolution, and overall warmth.

While testing the inks, I began using a CD balancing ring sold by Monster Cable.  Their rings came in four separate colors, red, green, yellow, and blue.   This was different, because the Sim-Audio rings were all, a rust brown color.  So, for the next application I experimented with combining each separate color ring, with the two inks.  When I used a different color ring with the same ink application, the presentation of the sound changed dramatically. Some combinations distorted it and some refined it.  I now had to discover how to best match each ring color with the multiple ink combinations that I could create.

I set out to design a treatment for every disc that I had, and I was amazed by the results.   This was revolutionary because, with so many options, I was able to come up with tuning combinations that improved each one of them.   What a blessing!  I had now created a way to improve the sound of compact disks, thereby making the medium enjoyable.

The Magic

The application of color has been the single most powerful modification I developed for compact discs.  After years of listening, I know that this was the major breakthrough that enabled me to achieve such stellar sonic performance with CDs.  My digital front ends eclipses all but a few analog front ends that I have heard, and I now have a hard time listening to analog records, due to there inherent noise and speed eccentricities.

My digital research is still ongoing, and I have made huge strides in the redesign of CD players.   My dedicated CD preamplifier is state of the art because I have herd no other preamplifiers that match its effortless synergy with digital sources.   As for my color research, it has progressed for over 20 years now, and It has gotten so specific that I use as many as 7 colors to tune a CD.  They are often combined in specific patterns that I created for the type of recording technology used.  Other applications for CDs that I combine with the color treatments are electromagnetic foils, freezing, and subtle energy treatments.  These modifications create compact discs that are just awesome, and you just have to hear the results to believe them!