Adventures in
"Tragedy"
As one who has a fairly large investment in vinyl
recordings, especially 45s, that will probably never be released on CD, I've always had an
interest in methods for reversing some of the damage caused over the years by mishandling
and playing on poor turntables. I've written about some of these in this space from time
to time, usually with a view to pointing out how to get one last good play so you can
record it.
One technique is always to play mono records in mono. With
the channels added together, any out-of-phase material cancels, and in mono recordings,
the only thing out of phase is noise. Another is to wet the surface before playing, as
this lubricates the stylus's contact with the surface, dramatically cutting noise as often
as not.
Removing the top frequencies with an equalizer can be
useful, too, as lots of old records have a good deal of high-frequency noise but very
little music in the highest octaves. There are also devices to remove clicks and other
annoyances, but these have long been off the market and show up only in second-hand sales
and suchlike.
My own invention -- others may have discovered it, of
course, but I never heard about it before I did it myself -- is to play mono records
through a Dolby Pro Logic surround decoder. Ordinary surface noise caused by damage or
dirt is almost always different in the two walls of the groove, so the decoder thinks they
are stereo and sends them to the front left and right channels. Many scratches cause
vertical motion, which the decoder obligingly sends to the surround channels. The actual
mono music, however, the decoder sees as center-channel material, and routes it to that
output, minus most of the "stereo" noise. It's this center channel you record.
While these methods, combined in various ways depending on
the nature of the damage, can improve the sound of most old records to a degree, they are
messy and time consuming and sometimes not effective enough to be worth the trouble.
Computers would seem to offer more elaborate ways to
extract the music from old grooves, and I had a vague understanding that there were
programs that used digital techniques to archive old analog recordings, but I had never
really experienced the process up close.
A couple of years ago, however, I received a note from one
Paul Gross, head of a nearby recording studio. Gross said that his company did a lot of
restoration of old vinyl, and I'd be welcome to a demonstration.
Gross knows his vinyl: years ago, another of his companies
operated one of the few vinyl mastering facilities in Canada. And the moment I arrived at
the studio, I realized I'd been there before, in August 1977, to attend a direct-to-disc
recording.
But today's exercise was not putting high-quality sound
into vinyl grooves, but extracting it. Gross suggested that I bring along a sample that
really needed work. I took several, but the one Gross and recording engineer Eric Abrahams
decided to tackle was a 45 of one-hit-wonder Thomas Wayne's 1959 song "Tragedy."
Most of my singles from that era are in pretty rough shape,
as my cartridges were of necessity cheap and the styli not changed as often as they should
have been. But on top of that, this one had suffered severe physical damage by being
played on an old-fashioned windup 78 phonograph. Tidying this one up would be nothing
short of a miracle, I thought.
In fact, when Abrahams put it on the turntable in the
digital editing and mastering studio, it didn't sound nearly as bad as I had remembered.
Later, when I tried it on my own table, it sounded about the same as at the studio, and I
concluded that I hadn't listened to it since I had the equipment of my youth. Simply using
better gear can often make an impressive improvement, even when it comes to things like
physical noise and distortion.
Still, there was no doubt that this was a seriously damaged
record, and Abrahams set out to clean it up, using the prodigious Pro Tools digital
recording and editing program and several associated restoration programs.
First, the record was simply played through an analog
preamp, then to an analogue-to-digital converter, and onto the computer. From that point
the disc could be refiled or ditched, as everything would be digital from here on.
The first step was to insert a high-pass filter at 25Hz to
remove any turntable rumble. This wouldn't be audible, probably, but it does soak up
energy and so is best removed.
The next operation struck me as a bit like sorcery. When
transferring the record, Abrahams had made sure he included a few seconds of the lead-in
grooves, as they contained the distinctive surface noise patterns of that record, but no
music. The computer could then analyze this noise and create bits of custom equalization
that would counteract each sort when it occurred. The result was a noticeable drop in the
noise floor with no appreciable effect on the tonal quality of the music. It didn't do
much to the distortion on musical peaks, but then it's not supposed to.
Then came the de-clicking program, to remove the effect of
scratches. As with all such devices, this has to be set carefully to avoid clipping off
bits of musical transients, but Abrahams managed to do it so that, to my ears, there was
nothing missing but the scratches. Finally a maximizing program assures that the recording
is at maximum digital level without going over.
Once all this processing had been done, the plan was to put
two versions on a recordable CD, the direct-from-vinyl recording, and the processed
equivalent. In listening, however, the processed version contained strange noises at a
couple of places, one a loud pop and the other sounding as though someone had
inadvertently blown into a microphone. For reasons that are not immediately clear -- to me
anyway -- these disappeared when the rumble filter was disabled, so the CD-R would contain
this version as well.
With disc in hand, I returned home planning to compare the
cleaned-up recording with the results of my own non-digital methods, with a virtually
unplayed re-release from the 1970s, and with a CD version from a compilation disc. The
re-release had to be scrapped because I immediately realized that it was a rerecording,
and the CD, although the proper version, was one of the worst transfers I have ever heard.
Both the treble and bass had been rolled off, and a spurious phony stereo effect added.
My own cleanup (wet playing and Pro Logic) was gratifyingly
successful, considering the condition of the original. But when I compared it directly
with the computer-processed version, it contained a great deal more noise than I would
have otherwise noticed. Given a better recording to start with, the digital restoration
would undoubtedly have been superb.
...Ian G. Masters
ian@mastersonaudio.com
|
