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Re: [ARSCLIST] Stereo records.
----- Original Message -----
From: "David Breneman" <david_breneman@xxxxxxxxx>
> --- Lou Judson <loujudson@xxxxxxx> wrote:
>
> > Curiosity quibble - isn't the groove on a 45 midway between
> > microgroove
> > and 78 size? Is there a specific name for it, or is it really
> > considered microgroove like Lps? I see a distinct difference,
> > visually... or is that just the larger excursion?
>
> In their original paper on the format, RCA specified "...a
> 1-mil radius as the minimum for the reproducer stylus and a
> 90-degree, 0.25-mil bottom radius groove" with a tracking
> force of not more than 5 grams. A PDF of the paper is here:
>
> http://tildebang.com/jukebox/rec_and_changer_comp_design_45.pdf
>
>
As it happens, that was also the groove size for mono LP's...so
both formats were generalized into "microgroove." When stereo LP's
first appeared, the groove size was dropped to .7 mils (.0007")...
dunno if this was for technical reasons or just to sell customers
more new needles...
Steven C. Barr