[78-L] runout spirals

[DAVID BURNHAM]

I'd love to see how spiral-outs and the eccentric groove were made.
particularly whether the latter was cut or molded in. (This is a special
curiosity of mine on Victor and HMV records from 1924 until the mid-30s
or so, when the pair of eccentric grooves were different diameters
depending on where the music ended.)

MS

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I had always wondered about this too but then it struck me that it isn't too 
difficult a thing to do.  There are two possibilities - either the recording 
stylus, after the music is finished, is activated by a cam to go through the 
eccentric groove motion to create the trip groove, and then moved ahead a 
millimetre or so and so activated again, or, the recording stylus disengages and 
a separate cutter, mounted on the same assembly is brought down to engrave the 
trip eccentric.  The latter case is more likely because I have looked at old VEs 
through a microscope and not only does there seem to be a break between the 
recorded groove and the eccentric, but the eccentric appears to have been cut 
from a much larger stylus.  There is, however, a short run-off spiral, (a 
fraction of a revolution), which moves away from the recorded material before 
the groove terminates.

I have also seen Columbia recordings which were originally issued on Viva~Tonal 
and then subsequently re-issued on standard mid-thirties or later pressings.  If 
you look at the run-off area, you can see the original Viva~Tonal run-off with 
the subsequent run-off spiral and eccentric groove super-imposed on it.  One 
must wonder, (at least this one must), how they managed that!

db