"Jim Lesurf"

Such behaviour isn't uncommon and is caused by the stylus being moved as
it
makes/breaks contact with the LP surface. It is 'harmless' provided you
lift or lower the arm with due care. i.e. slowly and vertically.



** Don't think that will help.

When a stylus first contacts the surface of an LP, it stops instantly but
the cartridge /arm keeps moving down until the stiffness of the cantilever
suspension supplies an upward force equal the downward one used for playing.
There may well be some overshoot in this "landing" movement and consequent
up/down oscillation before the mass/spring system comes to a complete rest.

If we assume the stylus downward speed permitted by of the lowering device
is around 1cm/second, then this is also the relative velocity of the stylus
during the initial part of the landing.

Now, a typical MM pickups deliver around 1.4 mV peak output when the stylus
velocity is 1 cm / second and during the stylus landing, the dominant
frequency of the transient generated by the PU is almost certainly sub
onic - likely concentrated in the range of 5Hz to 10 Hz.

So, the expected transient signal supplied to input to the phono pre-amp is
about 1.4 mV peak at around 7 Hz. A standard phono pre amp will magnify
this signal by the combination of its nominal 1kHz gain plus the additional
low frequency gain provided by the inbuilt RIAA curve.

Allowing a nominal pre-amp gain of 50 times and a further RIAA
contribution of say 10 times produces a circa 700mV peak transient at the
output.

700 mV peak is a level as great as or greater than typical playing levels
!!!

There will be a similar sub sonic transient whenever the same stylus "takes
off" - probably a bit worse as most stylus " take offs" seem to be a
little more dramatic than the landings. The analogy with aircraft is
singularly appropriate here.

BTW: The fact the stylus movement is mostly ( or possibly entirely) in the
vertical plane means the generated signals are in anti-phase in the stereo
channels.

Conclusion:

With the amp's volume control advanced to a moderate listening setting and
in the absence of a top grade sub-sonic filter included the system,
*expect* to see woofer cones do a bit of *exercise* during each stylus
take off and landing.




........ Phil