Rene, I think you are right on target with your question as I see you just stating it:
For example: For many years I owned and enjoyed an ET II tonearm. For all its many virtues, however, the implementation of its design allowed the arm to sag by as much as .006" from one end of its travel across the record to the other. The resulting change in VTA was clearly audible as the tonearm traveled across the LP. You could either have it exactly right at the center, or at the outside edge or in the middle, but not all the way across the LP. The result, with some cartridges, was an audible shift of soundstage as the cartridge tracked across the record, with some shift in tonality as well. My solution was to use a Grado Reference cartridge in the arm which was less fussy about critical VTA and enjoy the other virtues of the arm.
With my turntable today, and I can only speak to my turntable, it's a whole different situation. My turntable today is a Walker Proscenium, and this turntable has no variations of geometry across the LP playing surface. Given your interest and your background and training, I thought some technical information would be interesting to you, so I called Lloyd Walker to get some specific data on various measurements:
Platter: a 70lb lead platter machined flat to within "one-half of one-ten-thousandths of inch" across the entire platter surface.
Platter diameter: smaller than the lead-in grooves of the LP so the raised lip of the outer edge is OFF the platter; label area deeply recessed and larger than the label. Result is that the playing surface of the record lies perfectly flat on the platter.
LP Clamp: pulls the LP firmly down onto the surface of the platter so the LP is in continuous contact with the platter across it's entire playing surface.
Platter Bearing: Air bearing that maintains the surface of platter in a perfectly flat horizontal plane - their is no spindle so no spindle play, only a centering pin.
Tonearm: Air bearing tonearm that maintains a tolerance of "one-half of one-thousandths of inch" variance in height to the platter across it's entire travel. Rigid VTA and azimuth lockdowns to eliminate any structure flexibility or play. The set up time for the tonearm at the factory to achieve these tolerances typically takes about 2-hours.
VTA adjustment: Rigid and locked during play. Allows for continuous adjustment in amounts as small as "one-half of one-thousandths of inch" - 0.0005".
People sometimes wonder why a Walker Proscenium turntable is so expensive. It's expensive because it's built to these incredible tolerances. (Lloyd says the tolerances he demands are unique.) And those build tolerances are reflected in the incredible playback resolution this turntable delivers. This is the reason that, for me, VTA adjustments are not swamped by other aspects of the LP spinning on the turntable: that LP is spinning as virtually flat as is possible to achieve.
Hope you've found the technical data interesting. I did as Lloyd explained it to me.
With regards,
.
Why don't we hear the variation in VTA as the LP rotates, since this variation is much bigger than changing the armheight by .005'For some turntables, the geometries are such that the variations over the playing surface of the record can and do simply swamp efforts to be hyper-critical in setting VTA (and azimuth and VTF for that matter). Design and execution can allow arms to vary in height across the surface of the record, platters may not be flat, records may not sit flat against the surface of the platter (for a host of reasons), etc., etc. All of these will do exactly as you describe: create VTA changes that are far greater in magnitude than the adjustments Doug Deacon and I are talking about. You are correct to question this.
For example: For many years I owned and enjoyed an ET II tonearm. For all its many virtues, however, the implementation of its design allowed the arm to sag by as much as .006" from one end of its travel across the record to the other. The resulting change in VTA was clearly audible as the tonearm traveled across the LP. You could either have it exactly right at the center, or at the outside edge or in the middle, but not all the way across the LP. The result, with some cartridges, was an audible shift of soundstage as the cartridge tracked across the record, with some shift in tonality as well. My solution was to use a Grado Reference cartridge in the arm which was less fussy about critical VTA and enjoy the other virtues of the arm.
With my turntable today, and I can only speak to my turntable, it's a whole different situation. My turntable today is a Walker Proscenium, and this turntable has no variations of geometry across the LP playing surface. Given your interest and your background and training, I thought some technical information would be interesting to you, so I called Lloyd Walker to get some specific data on various measurements:
Platter: a 70lb lead platter machined flat to within "one-half of one-ten-thousandths of inch" across the entire platter surface.
Platter diameter: smaller than the lead-in grooves of the LP so the raised lip of the outer edge is OFF the platter; label area deeply recessed and larger than the label. Result is that the playing surface of the record lies perfectly flat on the platter.
LP Clamp: pulls the LP firmly down onto the surface of the platter so the LP is in continuous contact with the platter across it's entire playing surface.
Platter Bearing: Air bearing that maintains the surface of platter in a perfectly flat horizontal plane - their is no spindle so no spindle play, only a centering pin.
Tonearm: Air bearing tonearm that maintains a tolerance of "one-half of one-thousandths of inch" variance in height to the platter across it's entire travel. Rigid VTA and azimuth lockdowns to eliminate any structure flexibility or play. The set up time for the tonearm at the factory to achieve these tolerances typically takes about 2-hours.
VTA adjustment: Rigid and locked during play. Allows for continuous adjustment in amounts as small as "one-half of one-thousandths of inch" - 0.0005".
People sometimes wonder why a Walker Proscenium turntable is so expensive. It's expensive because it's built to these incredible tolerances. (Lloyd says the tolerances he demands are unique.) And those build tolerances are reflected in the incredible playback resolution this turntable delivers. This is the reason that, for me, VTA adjustments are not swamped by other aspects of the LP spinning on the turntable: that LP is spinning as virtually flat as is possible to achieve.
Hope you've found the technical data interesting. I did as Lloyd explained it to me.
With regards,
.
