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Re: arsclist Re: 45 rpm record groove depth
Chuck Howell, CA
Curator, Library of American Broadcasting
University of Maryland
College Park, MD 20742
Chuck Howell wrote:
> Does anyone out there in listserve land happen to either
> know the depth of a 45 rpm microgroove or know where I can
> find this information? This question was posed to us by a
> researcher, and we haven't been able to track it down.
> Width yes. Depth no.
Styli used to cut the grooves will determine the depth for a given width
measurement which is usually taken by a calibrated graticule microscope
looking at the edges of the land across the groove. A small included angle
at the stylus tip will result in greater groove depth whereas a larger
included angle will result in a lesser groove depth. Most 45's were cut
with the same stylus that LP's were cut with, the only difference being
setting to a greater groove width (and hence increasing the depth) to allow
for the higher recorded levels on the pop music discs that were being cut.
The included angle of the grooves were specified as 90 degrees +/- 2 degrees.
You'll get a good idea of the depth from that, less the radius of the cutting
... Graham Newton
Audio Restoration by Graham Newton, http://www.audio-restoration.com
World class professional services applied to phonograph and tape
recordings for consumers and re-releases, featuring CEDAR processes.