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Re: [ARSCLIST] ELP Turntable (was historical stylus rake angles)
One issue so far ignored is that of the physical compression by the stylus
of the shellac and vinyl at the point where it touched at great pressure,
however briefly, by the stylus.
This compression was expected by the system designers, at least at some
level of awareness, if unstated. Does removal of this pressure improve the
sound via the laser pickup improve the sound, not affect it at all, or make
it worse?
Similarly, my understanding is that 78s were cut at a zero degree tracking
angle and should be played back that way. Our cartridges are designed to
reproduce at the 15 degree rake at which LPs are to be played back. I'm not
sure this is true in all cases. When playing back a groove cut at one angle
and played back at another, logic says that one part of the wall will speak
before the other, consequently smearing the audio signal. In stereo, this
would give a continual meandering of phase. Does this actually happen, and,
if so, how audible are the results.
For critical work in my studio, my 16" SME is mounted on the helical driven
adjustible base that came with the Technics EPA series of tone arms. I can
move the base up and down while the record is playing. Trying it is a
feel-good exercise that occassionaly produces a clearer signal but is mostly
of no audio consequence.
What I find of greater audio impact is making sure the left-right cartiridge
angle gives even output from both sides. The grooves of many records are
not cut vertically and many more do not stay at their original angle. This
may be due to the cutting , the plasticicity of the pressing material or, as
I've come to believe, overly-compliant stlus twisting left-and-right as it
moves toward the record's center.
This may be due, at least in part, to cartridge design since all available
today are made for LPs. The catalever is made to mout a stylus to reproduce
a half-mill groove. The relationship of the stone's weight to the behavior
of the catalever is altered significantly when a heavier tip with, say, a
three mill point, is substituted. Add to that that the left-to-right
tracking movement of a lateral-cut groove is about 2.4 times more rapid than
that for which the design is optimized. I'm surprised we get as good a
sound as we do.
Grado made a stylus assembly with a long canatlever but it was supported
about half way down it's length, undoing whatever benefit it might have had
in this regard. I found it poor for 78s. I recall Ortophons that looked
truly vertical but have not worked with one in years. I've been using Shure
M-44s with which I tinker.
The laser, if its parameters were easily user adjustible during the playback
process, may offer improvement. And may not.
The electron microscope scanning process holds great promise. I've been very
impressed with the demos I've heard and with the folks conducting them. I
was told they could not attend this year's ARSC meeting due to a conflict.
Given its pattern of travel while it is taking photographs, its present
design can only work effectively on zero degree cuts. It will have to be
rethought for LPs so the camera stays in place, tilted at 15 degrees,
perhaps moving toward the center on a worm drive, while the turntable moves
in tiny increments. I should point out that though this process presently
delays the element of instant gratification by days, it is essential they be
allowed to get the process right and only then worry about streamlining it.
Steve Smolian
----- Original Message -----
From: "George Brock-Nannestad" <pattac@xxxxxxxx>
To: <ARSCLIST@xxxxxxxxxxxx>
Sent: Saturday, January 08, 2005 3:08 AM
Subject: Re: [ARSCLIST] ELP Turntable (was historical stylus rake angles)
From: Patent Tactics, George Brock-Nannestad
Jeffrey Kane wrote
My apologies, I should know to be more specific, especially with you lot.
:)
By noise, I'm referring to pops and clicks seemingly caused by dust,
sediment
and other contaminants. The player seems to be extremely sensitive.
Despite
the noise blanking feature pops and clicks still seem amplified far more
than
a conventional player, to the point of being intrusive. I don't find this
to
be as much of an issue with 78s (perhaps due to the larger groove
dimensions?), it's primarily an issue with "micro-grooved" material.
----- and several others have commented in a similar vein.
Now, the noise (impulse) signal we hear that originates from a groove
surface
has been severely processed by a) the preamplifier, b) the amplifier, c)
the
output amplifier, and d) the loudspeakers. Any of those components may
have
insufficient headroom and/or bandwidth for the task, because a minute
surface
imperfection reproduced by a velocity-sensitive system has a huge level
and a
very high frequency content - above 30 kHz is quite relevant. This means a
smearing in time of the noise pulse by any uncorrected band limiting, and
that makes it very audible. Michael Gerzon in SEVA's 38 kb mail of
yesterday
has a few words on this. So, unless you have a very large gain-bandwidth
product, local feedback rather than global feedback, hence fast overload
recovery, then your noise will be audible, irrespective of stylus origin
or
laser origin. Only with a stylus, in addition you have cantilever
problems.
And the loudspeaker must be of similar high grade - Quad electrostatics or
Magneplanar (or more recently Bang & Olufsen BeoLab5000 that works on a
different principle, but which is impulse-repsonse corrected). I fully
expect
the tests on the ELP that are upcoming (and I gather will be reported by
Eric
Jacobs to ARSC) to take the amplifier-loudspeaker chain into
consideration.
And if you cannot afford an ELP after having upgraded all the rest: even
your
stylus gramophone will sound better for it.
Kind regards,
George