Just wondering, along these lines...has anyone ever used an ELP laser
turntable (www.laserturntable.com)?
I wonder if it wouldn't make rake angles a moot point.
Steven Austin
(sorry Eric, for the flub to your email address)
-----Original Message-----
From: Association for Recorded Sound Discussion List
[mailto:ARSCLIST@xxxxxxx] On Behalf Of Eric Jacobs
Sent: Friday, January 07, 2005 11:50 AM
To: ARSCLIST@xxxxxxxxxxxx
Subject: [ARSCLIST] historical stylus rake angles (SRA)
Does anyone know of a reference where I might find historical stylus
rake
angles? Even some rough guidance on this list would be useful.
Note that SRA (the angle the stylus makes with the record surface) is
not to
be confused with the Vertical Tracking Angle (VTA) which is the angle
the
cantilever makes with the record surface. Of course, VTA and SRA are
directly related by the angle at which the stylus is mounted to the
cantilever.
Modern cartridges and tonearms are designed for SRA values of zero (ie.
a
vertical stylus, perpendicular to the record surface) or slightly
positive
to about 3 degrees or so. I realize that SRA values, like VTA, will
vary by
record label and need to be adjusted for each record for optimal
playback if
you are a perfectionist. SRA and VTA are primarily affected by record
thickness and cartridge height.
Variations in SRA (fractions of degrees) are most audible on LPs with
their
lower noise, wider frequency response and narrower grooves making VTA an
important adjustment for each LP.
How critical is SRA for accurate playback on acoustic or electric 78s or
transcription discs? Am I making a mountain out of a mole hill?
The reason behind my question is that the 1-2 inches of VTA adjustment
on a
tonearm will only compensate the SRA by a few degrees. In fact, tonearm
VTA
adjustment is best suited to compensate for variations in cartridge
height
and record thickness since it is assumed that the cartridge SRA is
correct
when the tonearm is level. If historical SRAs used rakes of 5 degees or
greater, some sort of custom cartridge mount would need to be devised (a
wedge shaped block or shim) to achieve the correct SRA.
Because of the limitations of tonearm VTA adjustment, it is not possible
for
me to experiment with large variations in SRA and listen for
differences.
Optical measurements of SRA are not possible with my 150x microscope
with
0.01 mm measurement reticle.
Thanks in advance to anyone who can shed some light on this question.
Eric Jacobs
The Audio Archive
San Jose, California