Turntable speed question........ - diyAudio
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Old 14th December 2013, 01:47 AM   #1
JoeDJ is offline JoeDJ  United States
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Default Turntable speed question........

I just checked my TT speed with a couple of of DL/printed strobe disks for 60hz.

There is absolutely no "wow".
However, it shows that both speeds are slightly slow by the same exact amount .....probably not enough to even notice.
This is with a new belt, clean pulley and platter... everything lubed and spinning freely.

So I checked my hz and discovered that it's 59.9 hz
My 66 year old brain is having a freeze....... Would that account for the slightly slow reading. or, would that make it appear faster?

Last edited by JoeDJ; 14th December 2013 at 01:55 AM.
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Old 14th December 2013, 03:01 AM   #2
DUG is offline DUG  Canada
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Is your motor a 60Hz induction type?

If it is then it will track your strobe and always appear slow...drive ratio issue.

If it is some other type of drive that is not derived from line frequency then it would show faster than 59.9Hz if actually accurate.

Either way it seems that it is actually slow.

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Old 14th December 2013, 03:19 AM   #3
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Your line frequency is probably far closer to 60 than 59.9; how good is your counter? Being belt drive, small errors in platter speed are likely. It's almost impossible to get the belt thickness just right for the pulley diameters so the platter speed comes out with no drift.
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Old 14th December 2013, 04:25 AM   #4
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If you feel you can, stick very very evenly one or two scotch tape turns around the motor pulley, then reinstall the belt and check speed. If done correctly should not wow at all and hopefully the speed will be spot on.
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Old 14th December 2013, 06:22 AM   #5
JoeDJ is offline JoeDJ  United States
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I found the problem.

The belt guide to change speeds was hitting the belt ever so slightly in both 33 and 45.

Pulling the lever back slightly so the guide does not hit the belt brings the speed up to perfect. .

Tomorrow I will see what I have to do to adjust it to bring it down a hair. .
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Old 14th December 2013, 07:20 AM   #6
JoeDJ is offline JoeDJ  United States
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Actually, I think that the motor pulley just has to be brought up a hair .

Probably the the rubber on the motor suspension had shrunk just enough over the years to allow the motor and pulley assembly to drop down slightly.
Maybe there's an ajustment for that .
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Old 14th December 2013, 08:57 AM   #7
AndrewT is offline AndrewT  Scotland
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A strobe that operates at mains frequency will always track mains frequency.
The turntable will hopefully turn at the correct speed/frequency.
If this frequency is "locked" to the mains frequency, then the strobe will ALWAYS indicate the SAME speed error.

Only when the TT speed and/or the strobe speed are NOT locked to mains frequency will the strobe indicate changes in the relative speed of strobe to TT rotation.
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Old 14th December 2013, 05:41 PM   #8
JoeDJ is offline JoeDJ  United States
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As it turns out, the motor suspension was fine .
I had to raises the pulley a hair and bend the guide away from the belt a bit..
Speed is now fine.

I also played some piano and did not notice any flutter.

Last edited by JoeDJ; 14th December 2013 at 05:48 PM.
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Old 14th December 2013, 06:08 PM   #9
tinitus is offline tinitus  Europe
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as I remember it, a tiny bit slower speed gives better timing, rythm, and 'sonics'

or ... maybe its really the opposite
just a tiny bit too fast, and all the good musical stuff is gone

and I believe that is a main problem with all modern music 'reproduction'
but with new and better digital technology this may be changing soon
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Old 14th December 2013, 06:18 PM   #10
kevinkr is offline kevinkr  United States
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Best IMO to playback at the proper speed, obviously if the cutting lathe was running off speed all bets are off unless you have some range of adjustment and know by pitch whether you are on speed or not.

I don't buy that playing off speed is going to be an improvement, but small errors are probably undetectable in practice.

Back when I was restoring my MIT flea TD-124/I basket case I used it as a source for an audio get together, it was running several % slow and while I could tell, apparently I was the only one - the strobe and speed adjustment linkages were not fitted at that time and I had to adjust it manually with a vinyl engine strobe I printed out for the occasion.. The strobe confirmed it was running slow, and reaching under the table to adjust it was a royal pain. Lots of curious looks and comments from the well beered crowd.. lol
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