[Mark]

On Oct 23, 4:01*pm, "Paul Stamler" wrote:
"Edi Zubovic" wrote in message

...

-- I think this could be a sort of cutter pinch or some other
cutter/lacquer issue. You see it beginning in the ultrasonic area at
the outer rim of the record, and falling down as the cutter travels to
the end of the record. First I thought that the two walleys would
roughly co-respond to the two geometrically most clean spots of an
record but it seems that they rather change with dynamics.

There aren't any particular dynamics on this disc -- everyone plays at the
same volume throughout, as is often the case on acoustic recordings.

The pitch
is IMO lowered as the cutting geometry changes towards the end of the
recording. At the other hand, I've seen mirror reflections near the
Nyquist frequency when analysing a high frequency sweep tone.

Well, the cutting geometry *shouldn't* change at the end of the recording,
since it's a straight-line lathe. On the other hand, there does seem to be
more loss of high-frequencies than usual toward the center grooves, which
suggests that the cutting assembly may not have been mounted at the proper
angle. Whether that has anything to do with this artifact, I don't know.

Peace,
Paul

well, as I'm sure you know, while the disc RPM remains constant at
78RPM, the TANGENTIAL VELOCITY of the surface relative to the stylus
reduces for grooves closer to the center.

Mark