The modern Lp has grooves that are nominally 1 mil (1 thousandth of an inch) wide. [I say nominally because the specification refers to the measured width about half way down the walls of the V-shaped groove, typically the contact points for the stylus as it rides in the groove.] Electrical era 78 grooves are 3 mils wide. Earlier disks can have grooves even wider (4 to 5 mils), and one-off transcription disks can vary between 2 to 4 mils. Radio transcriptions will usually have 2 mil grooves if they are laterally cut, but many vertically cut transcription discs from the 1930s have 2.5 mil grooves.
...But nowadays, little wear is caused by higher playing weights; most is caused when the grooves vibrate the stylus, not by the downward pressure. There can be several advantages in increasing the downward pressure for an archival transfer. The fundamental resonant frequency of the cantilever is increased (according to a one-sixth power law - Ref. 21), thereby improving the high frequency response. Clicks and pops are dulled, partly because the stylus can push more dirt aside, and partly because the cantilever is less free to resonate. But most important of all, the stylus is forced into the surface of the disc, thereby increasing the contact area and reducing the basic hiss. Obviously the operator must not risk causing irreparable damage to a disc; but if he is sufficiently familiar with his equipment, he will soon learn how far to go whilst staying within the elastic limits of the medium.
Shellac discs seem practically indestructible at any playing-weight with modern stereo pickup cartridges. Modern pickup arms are not designed for high pressures, but a suitably-sliced section of pencil-eraser placed on top of the head-shell increases the down-force with no risk of hangover. Pressures of six to ten grams often give improved results with such discs; special low-compliance styli should be used if they are available. With ultra-large styli, like those for Pathé hill-and-dale discs, it may even be necessary to jam bits of pencil-eraser between cantilever and cartridge to decrease the compliance further; twenty to thirty grams may be needed to minimise the basic hiss here, because the area of contact is so large.
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