Then why measure at all? And why use a PC with spectral analysis software. Why make the statement that you find 33.30 to 33.36 to be satisfactory? If you are going to measure, why not do it as accurately as possible? Does anyone complain that their Fluke DVM is too accurate? Personally, I only look at the number of decimal places that are relevant to the task.
Correct. Nobody said anything about rounding?
Fair enough. In my experience, static stylus drag (stylus down vs stylus up) shows up as a drop in speed of 0.01RPM or less. Without 3 places right of the decimal, this would be almost undetectable. The drag is almost entirely a function of belt creep, not slippage as you implied. Slippage can be cured with proper tension, creepage cannot. David's table uses a semi-rigid belt which suffers from much less belt creep than an elastic belt, so I doubt there would be any difference between stylus up vs stylus down, and if there was, it would occur at a much slower (inaudible) rate than with a lighter platter.
Dynamic drag is another story (change in speed with loud or dynamic passages vs soft). I'm not able to measure it even with 3 places right of the decimal, but in theory it exists. Even direct drive synchronous motor driven platters can suffer from this as the angle between the rotor and the magnetic field can vary with torque. The only reliable cure for this IMO, is platter mass; by definition, dynamic changes will be short lived, so the higher the inertia, the smaller the change in speed due to dynamic drag.
My point was simple since start - a good strobe with a quartz strobe flash light is all that is commonly needed to listen to vinyl. I am just thinking that most of our members consider that listening to their tapes is listening to their best source . Are they troubled by how accurate is the speed of their machines?
I don't know, are they? I'm not aware of any reliable way to measure it and if one exists, there's not much they could do about it if the speed was off.
That's because the motors are servo-locked and the data is buffered, so playback speed is a function of the master clock, not a rotating disk. High end CD players use low phase noise oscillators to reduce jitter which can be measured (in the nano & picosecond range) and by most accounts, jitter does adversely affect sound quality.
