I recently was given about 600 LPs, of varying material. After eliminating
Mrs Mills Piano Party, Suddenly it's Des O'Connor and The Hits from the
shows played on the Kazoo, I have got about 150 classical LPs in pretty good
condition, even though many go back to the early 60s and a few to the late
50s.

Some of the RCA discs have the Dynagroove system, which, if I remember
correctly, involved pre-distorting the recording to compensate for the
tracing distortion of a 0.7thou spherical stylus. The system wasn't taken
up by other labels, and anyway, 0.5thou sphericals soon were available as
were ellipticals, rendering the system unnecessary.

Playing the LPs with my cartridges, all of which have line-contact styli, I
would have expected that the treble would have sounded more distorted than a
non-Dynagroove LP, but in fact, these seem to be quite clean at the top,
certainly no worse than others.

Does anyone know the detail of how the Dynagroove system worked, and what
effect it would have on being played with a modern non-spherical stylus.

Thanks

S.