"Leif Neland"

"* Makes no difference at all."

How could you claim to be any kind of engineer and say that ?
OK supposedly smart ****, design an oscillator with negative feedback
instead of postitive and see how far you get.
You have to take into account the speed of sound and the distance between
speaker and pickup.

It does not matter if the speaker is in phase or not, it matters what the
phase of the soundwave when it hits the record a little later.


** If low frequency sound waves were vibrating the LP direct - there would
be no fix other than removing the TT from the room. So this is not the usual
case.

Turntable feedback IS a result of the room's *structure* vibrating in
sympathy with standing waves at particular
wavelengths - mainly the floor if the TT is supported by that OR the walls
if a shelf is being used. The frequencies of such standing waves depend on
the room's dimensions and the speed of sound.

Any TT must be isolated from these vibrations and the oldest and by far most
effective way is by use of coil spring.

IME, the ideal set up is 3 conical springs and enough weight above them to
result in vertical oscillation at about 2 Hz. When displaced, the TT system
should move freely and oscillate up and down for a couple of seconds - so
any connecting cables must be looped and able to follow the movement easily.
No damping material should be used.

If done correctly, room surface vibrations no longer affect the TT - even
jumping on the floor - so the chance of actual feedback is eliminated.


.... Phil