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Turntable speed accuracy

There is another thread (about the NVS table) which has a subordinate discussion about turntable speed accuracy and different methods of checking. Some suggest using the Timeline laser, others use a strobe disk.

I assume everyone agrees that speed accuracy is of utmost importance. What is the best way to verify results? What is the most speed-accurate drive method? And is speed accuracy really the most important consideration for proper turntable design or are there some compromises with certain drive types that make others still viable?
peterayer
dover
2,273 posts
 
Hi Henry -
Have finally managed to try the Sutherland Timeline on the Final Audio TT ( heavy mass - platter 19kg, string drive ( single silk thread ), AC motor driven by oscillator preamp( reconstructed sine/cosine waves) and power amp.

Testing with and without the record playing I have to adjust for stylus drag.
Both the KAB and the Timeline show the stylus drag. The net movement of the laser with stylus drag is about 2mm on the wall per rotation.

If I correct for stylus drag with the KAB then recheck with the Timeline it is spot on.

With record playing the Timeline is spot on as per the KAB.

Conclusions are I can sleep at night, and the KAB, or at least my one, is as accurate as theTimeline.

halcro's avatar
halcro
2,664 posts
 
Hi Dover,
Congratulations. Good to hear :-)
lewm
13,357 posts
 
"2 mm on the wall" is meaningless, unless you tell us the distance from spindle to wall surface, but in any case it sounds like the effect of stylus drag is very tiny, probably not audible and probably not worth worrying about. Unless I misremember some of the earlier posts, it sounds like the Final Audio, as you have equipped it, is among the best of the belt-drives in terms of resisting stylus drag.
atmasphere's avatar
atmasphere
11,977 posts
 
I picked up a Timeline as I was interested in how our Scully Lathe was doing while cutting lacquers.

The Scully uses a 1/8 horsepower Bodine AC synchronous motor, driving a transmission that then drives the platter via a drive shaft.

With the cutterhead cutting on the plate, the laser does not move- over the entire side you can't see the change even when you use a micrometer. Not bad for being built in the 1940s :)
dover
2,273 posts
 
Atmasphere - think of all the "wear and tear" of all the drive train over 70 odd years. I think whilst we have gained in technology, we have probably lost ground in metallurgy, it's the age of junk metals ( PC & non toxic manufacturing processes required ). I still marvel at the lack of main bearing wear in the Final TT which is now over 30 years old.
Love to hear playback via a lathe and good old Mcintosh MI200's that I lusted after years ago.

Lewm - distance from wall is 400mm if you want to do the maths.

Henry - just to say thanks for the inspiration - your video challenge has really upped the game for die hard analogue folk.
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