A TUNE-UP FOR THE DUAL TURNTABLE - ThaiHDbox

Try, Try Again
By Barry Fox
�n 1982, right at the end of the
golden age of vinyl, Teldec (the
company jointly owned by Telefunken
and Decca) experimented with
a completely different way of cutting
hi-fi LPs, called Direct Metal Mastering
(DMM). This had spun off from
the work done by Teldec, at a semisecret
lab in North London run by
Decca’s respected recording engineer
Tony Griffiths, on TeD—a floppy video
disc. The TeD video disc had a superfine
hill-and-dale groove cut in a flimsy
plastic disc about the size of an EP. The
disc spun at 1500 rpm and played ten
minutes of color video when tracked
by a mechanical sled-shaped stylus.
Panasonic killed TeD with Visc, a rigid
12� LP that worked in much the same way
as TeD to deliver an hour of color video
from each side of the disc. Visc was mindbogglingly
clever but was soon killed by
JVC’s VHD, which used a grooveless conductive
plastics disc tracked by a capacitive
stylus, and by RCA’s CED Selectavision
which used a grooved capacitance
disc. Both came to market but were soon
killed by Philips’ Laservision/Laserdisc,
the optical video disc that later spawned
CD, DVD, and Blu-ray.
But when TeD died, Teldec adapted
the video disc cutting system to audio
mastering. The object of DMM was to
eliminate the perennial problems with
master lacquers, such as faulty blanks
and blemishes caused by the first
stages of electroplating. With DMM, a
diamond stylus cuts the groove directly
into an amorphous copper metal coating
on a blank stainless steel disc. There
is no memory effect—relaxation of the
plastic with high frequency loss—and
the first stage of electroplating is taken
out of the process, which reduces the
risk of plating errors. DMM also made
it possible to pack grooves tighter,
thereby increasing playing time by 15%.
The heads which cut soft lacquer
need several hundred watts of driving
power, so you can imagine what
it takes to cut copper metal. Teldec
used a modified Neumann stereo cutting
head, and, to help the stylus cut
through the metal, superimposed an
ultrasonic signal of around 70kHz on
the audio signal being recorded. This
acted in much the same way as the bias
in a tape recorder, which shakes up the
magnetic particles. The bias signal used
for the DMM process mechanically excited
the diamond-cutting stylus.
In July 1982 Teldec offered to license
the system to any record company, for
a one-off fee. Between 1982 and 1986,
Melodiya, Virgin, and PR records each
signed to use the system.
By 1985 the hi-fi press was already
worrying that the high-frequency bias
might cause audible “beat” effects.
There was talk of DMM cuts having a
certain characteristic “sound.” And by
then the record companies were cutting
back on LP production, in favor of CDs.
Not daunted, Teldec came up with
a modified system for direct cutting
Compact Disc masters. DMM CD was
unveiled at the Los Angeles Audio Engineering
Society Convention in November
1986. But DMM CD also stalled. It
proved difficult in practice to cut metal
masters with a pit shape that accurately
mimics the pits produced by the
E12 audioXpress 12/10 www.audioXpress.com
conventional technique of laser-cutting
and etching a glass master coated with
photo-sensitive material. The difference
in pit shape can confuse the laser
optics in some domestic players.
Mechanicaly cutting CD masters
would now be a pointless exercise. But
perhaps the time is now right for someone
to try DMM LP mastering again.
STORAGE RIGHTS
If you’re using a home server to store
high-quality audio, spare a thought for
a recent court case in the US.
The Hollywood studios have won a
$4.5 million punishment payment from
RealNetworks—the US company behind
RealAudio compression—for selling $30
software called RealDVD that rips copyprotected
optical discs to hard disc.
Don’t think this doesn’t matter to
you just because you don’t want to rip
video. Blu-ray is a very high-quality music
disc, but its AACS anti-rip system
and regional coding lock sound and vision
far tighter than DVD or CD.
Indeed it was the promise of Bluray’s
allegedly un-hackable protection
that appealed to the software industry
after DVD’s allegedly un-hackable CSS
was hacked by a schoolkid. As we in
Europe saw when Nelson Riddle’s classic
score for the 1966 Batman movie
was released as an audio-only “extra”
on a Blu-ray disc only in the US, regional
coding for video can tie up audio
content as well.
Imerge (www.imerge.co.uk) pretty
much invented the hard drive music
store product category. “We developed
the first audio server in the 1990s and