As far as I know 45s always used a microgroove cutting stylus. On singles
under 3 minutes we cut a 5.5 mil groove although 4 was considered normal.
LPs were, of course, packed tighter. Playback styli would be the same as for
LPs with the smaller ones being better for stereo because they rode lower in
the groove.

Bob Olhsson Audio Mastery, Nashville TN
Mastering, Audio for Picture, Mix Evaluation and Quality Control
Over 40 years making people sound better than they ever imagined!
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-----Original Message-----
From: Association for Recorded Sound Discussion List
[mailto:[log in to unmask]] On Behalf Of Steven Smolian
Sent: Sunday, August 14, 2011 3:28 PM
To: [log in to unmask]
Subject: [ARSCLIST] 45 groove size

Originally 45s were mono, cut with a one mil groove. All vertical signal
was noise.
 
At some point (no pun intended- well, maybe) it matched that of the stereo
LP, even when the signal was mono, i.e., .5 mils.
 
When did this happen?
 
I'm not discussing EPs, stereo 45s, etc., just your nommal, get the biuck
out of the teenager's pocket 45.
 
Steve Smolian