[78-L] 78 grove spacing

[Malcolm]

Glad you're enjoying the book, Ingo.
Without doing Patent Office research I am not sure when lead screws came 
into existence on record cutting lathes - fairly early I'd think - but 
the engineer could choose from a variety of pitches from fine to coarse 
depending on the recording's needs. I do know this could be done by the 
1930's when (electric) instantaneous recording came onto the scene.
And mastering engineers were still using a microscope to check the 
groove for errors well into the 1960s.
Of course I'm doing this by memory so any errors are strictly mine!
Malcolm

*******

On 8/16/2019 7:59 PM, ciadelgramofono at yahoo.es.invalid wrote:
>   Very interesting, and thanks Mal, for this enormous book!
> First time I owned one of those DGG 'Variable Micrograde 78' records was in the 80s, a single 12" record with the Dvorak's 'Neue Slawische Tänze'. It certainly lasted much longer than a standard 78, and I believe the groove is finer too, for it can be played with an LP stylus. Later I traded it for other records (hard student-with-limited-budget times).
> Recently I've acquired another one, and I've also noticed it's longer duration (exact data not at hand). It's also very tough, not sure if the material of the record is current shellac or a more advanced plastic, not exactly vinyl... The surface is very soft, but the record is heavy as a shellac one.
> BTW, in a different fashion, I've also noticed that late 1930s Vocalion records also exhibit a greater groove spacing towards the end of a side. Very characteristic of them, not for the red Columbias, but the blue Vocalions, and seems something different, not related to the musical contents of the grooves.
> Inigo
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