"François Yves Le Gal" wrote in
message news
On Thu, 7 Sep 2006 15:40:40 -0400, "Arny Krueger"
wrote:
No turntable has precisely the correct speed. Every
real-world turntable is always a little off, one way or
the other.
Hence the proviso :"taking or leaving minute amounts of
wow and flutter".
A completely relevant issue, but one which regrettably does not include the
long-term speed inaccuracy that I'm talking about.
And, to tell the truth, the direct-drive tables have some speed accuracy
errors of their own. However, they use a tachometer on the turntable itself.
I've never seen a belt-drive system with a tach on the turntable platter
providing feedback to the motor speed control. The stretchiness of the drive
belt raises some issues from the standpoint of nyquist stability. Direct
drive tables lack this problem for obvious reasons.