Posted by Jon Risch on April 18, 1999 at 11:23:16:
In Reply to: Re: Corrections and Additions posted by TAFKA Steve on April 18, 1999 at 07:51:06:
To the best of my knowledge, unless you were to coat the entire stylus with a paint or dye (or majic marker), and then play it to rub some off, you would not be able to actually see the contact patch at all with the naked eye, and perhaps even then it would require magnification. I typically used a 3-30X power stereo microscope to look at stylii when I worked on Denon catridge QC and repair checks, and even then the contact patch was not obvious unless there was enough wear to make the stylus require replacement.
Regarding the alignment of the stylus, the entire diamond chip, typically a square shanked piece of diamond placed through a square hole in the cantilever (usually laser cut hole) is indicative of the alignment of the contact patch, with a few exceptions. If you can backlight the cartridge, and look at the gross angle of the entire stylus shank, then you can see the SRA, as the contact patch is almost always aligned with the shank.
As for a stylus shaving off vinyl, this will usually only happen under worn or faulty conditions. If the diamond is chipped, which can happen of the stylus encounters a piece of silica grit or some other hard piece of "dust" in the groove as it is playing, then the edge of the stylus can become chipped or damaged and become an instrument of album destruction. The other way is when the stylus becomes so worn that a flat is visible on the stylus edge, and the alignment of the cartridge is changed, even a little, then the edge of the flat is now at a different angle than it was, and could start digging in and shaving or scrapping away vinyl.
YOU MUST EXAMINE A STYLUS UNDER A MICROSCOPE FOR WEAR, and if you can see a flat spot, the stylus needs replacing. A stylus near the end of its safe usefull life will have a rounded flat spot, and should also be considered for relacement (think of how valubale your vinyl is now that it is essentially irreplacable!).
Finally, Last as well as Sound Guard, were found to be problematic in most cases. If you applied enough to actually reduce friction and wear, then you have applied enough to actually reduce HF content and transient information. Tests conducted at the Discwasher research labs (conducted by yours truly) show that the harmonic structure of a square wave would change upon application of Last or Sound Guard, and that the harmonic structure would continue to change until after a dozen plays or so, after which the higher harmonics had been reduced in amplitude, and the very highest (lowest level) would dissappear entirely. Tests on other signals showed that signal levels of -60 to -70 ( I was able to routinely recover signals and groove information down to -70 dB and even a little below, on a good record with an exactingly set-up MC cartridge, with a consistent noise floor of around -75 to -80 dB on virgin Denon pressings and on audiophile albums) would be covered over by the application of these treatments. Sound Guard did seem to be worse than Last, but they both did it.
Jon Risch
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