From: Patent Tactics, George Brock-Nannestad
Mike Biel wrote:
> Theoretically the best sound at 78 would be with a microgroove size
> groove since it would be capable of higher frequency response than a
> wide groove, or a microgroove at slower speeds.
----- now, I am speculating why this should be so. I do not understand why a
microgroove should give a higher frequency response than a NORMAL groove. It
has to do with the maximum acceleration of the tip and the ability of the tip
to trace precisely the groove shape. If the smaller radius of an elliptical
stylus (or the radius of the edge in a line contact stylus) is able to trace
without error a curve in one flank of the groove, it does not matter where
the other flank of the groove is.
If microgroove is associated with a higher groove pitch (which would mean
well above 200 grooves per inch), then the maximum amplitude would be reduced
compared to the ca. 100 grooves per inch in a traditional 78 rpm record. If
we maintain the 100 grooves per inch but reduce the groove width and depth,
we would have more land to use, and the modulation could be higher, which
would give a low frequency advantage. That is the rationale behind disco
singles (albeit at 45 rpm). And all of this without variable groove pitch. If
that is used, then we are even better of, bass-wise.