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In Reply to: Null points for 7" discs? posted by Damián on July 4, 2017 at 21:36:06:
I just found a spec sheet that provides the minimum and maximum modulated groove diameters for a 7" disc. You can find it at the following link:RIAA Dimensional Standards for Phonograph Records
The minimum and maximum groove diameters for a 7" disc translate into the following groove radii:
Innermost Groove Radius = 53.975-mm
Outermost Groove Radius = 84.1375-mmThe following Null-Point radii will provide the lowest tracking error distortion for a 7" disc:
Inner Null Radius = 56.97-mm
Outer Null Radius = 77.77-mmThe optimum null-point radii for any size phonograph record are based on its modulated groove envelope. You need to know the radius of the innermost modulated groove, r 1 , and the radius of the outermost modulated groove, r 2 . Then you can apply the following equations to find the null-point radii that will provide the lowest possible tracking error distortion within that modulated groove envelope.
Good luck,
John Elison
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Follow Ups
- RE: Null points for 7" discs? - John Elison 07/5/1706:53:41 07/5/17 (12)
- RE: Null points for 7" discs? - flood2 17:03:29 07/5/17 (11)
- RE: Null points for 7" discs? - John Elison 18:26:48 07/5/17 (10)
- RE: Null points for 7" discs? - flood2 16:20:50 07/6/17 (9)
- RE: Null points for 7" discs? - John Elison 18:13:38 07/6/17 (8)
- RE: Null points for 7" discs? - flood2 20:27:04 07/7/17 (7)
- RE: Null points for 7" discs? - John Elison 21:41:46 07/7/17 (6)
- RE: Null points for 7" discs? - flood2 02:42:06 07/8/17 (5)
- RE: Null points for 7" discs? - John Elison 15:31:58 07/8/17 (4)
- RE: Null points for 7" discs? - flood2 21:38:06 07/10/17 (0)
- RE: WHOA WHOA - Damián 09:21:23 07/9/17 (2)
- RE: WHOA WHOA - flood2 21:55:00 07/9/17 (0)
- RE: WHOA WHOA - John Elison 21:34:40 07/9/17 (0)