[net.audio] Wear on cartridges -- old story and a question.

mat@hou4b.UUCP (07/14/84)

Some years ago, when Columbia records were known for quality (before my
time :-) ) they had people pull every thirtieth record or so off the line
and play them.  These poeple were allowed to change styli as often as they
liked.  They usually changed them after about four hours.

Some management type had the discards checked under a microscope, and no
wear was visible, but some kind of blind tests were done and the practiced
listeners could indeed tell quickly how worn they diamond had become.

By now, I'm sure that the proper microscope techniques were discovered.

The question; a month or two ago I went to get my moving-coil cartridge
replaced.  The saleswoman checked it under an Audia-Technica microscope,
which uses a small, powerful, light source on each side reflectiing off
the groove-reading face to create a little dot.  She asked if I was
sure I wanted to replace it.  I haven't got an elapsed time meter, but
estimated that I'd played between 170 and 220 sides with it, so I said yes.
She invited me to look at the microscope image, and compare it with the
photos of what one should expect.  The traces were ever-so slightly
distorted, sort of like this:  \ \  rather than like this: | |
but clean, with no rounding, comet tails, or whatever.  I said change it.

Now for those who know about such things, did I read the microscope
image correctly?  Are such things meaningful?  Etc.