That last image isn't accurate.
"It isn't really "two sides". The two channels are cut at right angles to each other, each at a 45 degree diagonal to the record plane. The polarity is such that the sum of the channels -- L+R -- causes left-and-right groove wiggles while the difference (L-R) causes up and down. <BR><BR>This was originally very important for compatibility with the huge installed base of mono pickup cartridges -- a mono cartridge is sensitive only to the left-to-right wiggles and so automagically picks up the L+R signal. Of course it was later found that mono cartridges typically had poor compliance in the vertical direction and so would chew up the groove bottom... <BR><BR>Incidently, the two channels aren't all THAT separate. Crosstalk in phono playback is only around 30 dB."
I took some very high res SEM and phase contrast light microscopy images of vinyl grooves and CD pits back when digital was getting popular in the 80's. CD pits aren't all that pretty, but a high res image of a vinyl groove is a thing of beauty.
Direct to Disc vinyl is pretty amazing although I'll admit that modern digital can also be amazing and is the future. For now anyway.
