"Dave Platt" wrote in message
...
I've read that this sort of LP pre-echo can occur as a result of the
original lacquer-cutting process during the making of the master. The
cutting stylus cannot do a perfect, side-effect-free job of cutting
the groove - that is, it cannot magically remove the unwanted portion
of the lacquer while having no effect at all on other portions of the
lacquer. There's some amount of "pushing aside" action, which
deforms the un-cut part of the lacquer - pushing some of it "inwards"
(towards the as-yet-uncut part of the master disc) and pushing some of
it back "outwards" (towards the groove that was cut one revolution ago).

If the pitch between the grooves is too narrow, this pushing of the
lacquer will have the effect of deforming the inner wall of the
previous groove... in effect, "imprinting" the modulation from this
groove upon the previous groove.

This unwanted adjacent-groove modulation effect becomes a permanent
part of the lacquer, is carried over into the metallization process
and the the creation of the mold/stampers, and is molded into every
piece of vinyl created from those stampers.

Yep, just one more reason to prefer CD's :-)

MrT.