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!
