RichP714 wrote:Back in the day, there were a couple of different stylus shapes that were intended to deal with groove wear, some of them shaped to have the contact point lower in the groove than typical and thereby avoiding the 'worn' walls of the groove from other styli. IME these typically 'found' more deeply embedded dirt, but yes, the walls of the groove are modulated the same along it's depth (to the extent that's possible)
I touched on this briefly in another thread about turntables and player old vinyl. There were 3 basic stylus shapes back then: Conical, Elliptical and Multiradial.
The electrically heated cutting stylus that is/was commonly used had a triangular shape with extremely sharp vertical contact patch (it had to actually cut the laquer master after all) which created the original V groove shape that everyone knows. The problem with using the same shape to reproduce sound was that it would actually chew chunks out of a vinyl record while playing so they came up with the 3 different shapes that still exist today.
Conical, when viewed in cross section looked like a circle and its single radius meant that the contact points of the stylus were very small and smooth, typically .007" in radius (if memory serves me right, though here I am using it as a relative value).
(please excuse my crude drawings which are not to scale)
Elliptical styli and an oval shape when viewed in cross section, but also had a larger vertical contact patch and usually rode a bit lower in the groove. Cheaper ellipticals typically had a ratio of .007" X .004", the better ones going all the way down to .007" X .002". The sharper edge made it easier for an elliptical stylus to better follow the sharper curves of high frequency notes on a record.
Multiradial styli had a variety of shapes that most often ressembled a sideways diamond shape with rounded corners and a much longer vertical contact patch that rode even lower in the groove, theoretically making it possible to pick up portions of the groove that had not been damaged by conical or eliptical styli. The almost razor sharp vertical contact patch of the multiradial styli allowed much higher frequencies to be reproduced at times up to a maximun or 40khz which was used with discrete 4 channel recordings (the 2 rear channels using the bandwith from 20khz to 40 khz).
2 main vendors were responsible for the vast majority of multiradial styli back then: Audio Technica with its Shibata stylus (almost ressembling a severely flattened heart cross section) and Bang & Olufsen/Ortofon with their Quadraradial (hope I got the name right) stylus. A few other high end Japanese cartridge makes made their own variations of these designs (some actually bought their diamonds from Audio Technica). Most of the large American companies also made variations on these basic shapes including Shure, ADC, Empire and Stanton, but none of them enjoyed as much commercial success as the 2 major players.
The whole point behind my earlier recommendation for using a Shibata cartridge to play back older records is that IF
they are properly cleaned, then dirt and gunk in the very bottom of the grooves isn't a problem and the sharp stylus will read from an undamaged portion of the groove, thus restoring the original sound of the vinyl record. Records wear at the contact point, so the longer the contact point, the less wear the record gets.
As far as that laser vinyl player mentionned earlier, wear would not be an issue nor would heat for that matter, so the record would not melt nor any damage whatsoever occur. A CD or DVD doesn't melt when it is played in a laser player, does it?