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SME speed adjustment

I have been reading with much interest the thread about speed accuracy and the Timeline device.

I have an SME Model 10 turntable which has no speed adjustment on the motor controller. I use the KAB strobe and my table is fine, but I fear that if I have the chance to check it with the Timeline, and the speed is off, I will not be able to adjust it, so the exercise would be futile anyway. Currently, when the speed changes over time, I replace the belt, as SME suggests and this usually works.

Could someone suggest a method to adjust the speed on a motor controller that does not have such an option? Is there an aftermarket device that can be used to alter the voltage to the motor controller or some other method?

Any advice would be much appreciated. Thank you.
peterayer
brf
1,715 posts
 
The only way to adjust the speed on an AC motor is vary the frequency of the AC which powers the SME 10. To do this, you will need an external motor controler like the Walker or VPI SDS.
cdk84's avatar
cdk84
70 posts
 

Or, Peter, a Variac, as we described. They are available on ebay or easily from scientific supply houses if you would like a used one.

Best to You in your Search,

David
brf
1,715 posts
 
A Variac will not work to adjust the speed of an AC motor. AC motors are synchronized with the frequency of the AC supply current. A variac only alters the voltage, not the frequency.
halcro's avatar
halcro
2,664 posts
 
You may be worrying needlessly Peter?
It is not necessary to have the turntable revolve at precisely 33.33rpm to have good sound.
Orchestras around the world don't always base their pitch on the note A being at 440Hz. Anywhere +or-12Hz in pitch is quite acceptable.
This would relate to a shift in the Timeline mark on the wall of up to 1/2" every revolution of the platter.
As long as this shift is consistent.......you will have no speed-related issues.
The only way to find out....is to buy/borrow a Timeline.
The 'fear' is much worse than the knowledge :^)
Good luck.
ketchup
699 posts
 
This would relate to a shift in the Timeline mark on the wall of up to 1/2" every revolution of the platter.

To make that statement, you also need to state the distance between the Timeline and the wall, don't you? At what distance from the wall does 1/2" of shift per revolution correspond to +/- 12Hz?
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