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Speed Stability

I have been fretting about the speed of my vpi for about a week now. I do not have a test LP or a strobe mat but I feel that if there is a speed issue. I am hearing the pitch fluctuate up and down on notes that are held out. I have compared some recordings to a CD version and have gotten mixed results. For instance:

On the first track of John Coltrane Quartet Ballads, I noticed that the ending note on the the first track tended to sway like an old VHS tape compared to the solid pitch of the CD version.

a first pressing of Dark side of the moon compared to my anniversary CD copy resulted in no significant changes in pitch that I could hear.

I guess what Im trying to get at is could that be a issue with the speed of the pressing itself, or could it be that some records show off a problem with my rig more than others. I hope it hasnt just started to be a thing thats just in my head. I think my next step is to take the Coltrane over to my fathers direct drive technics and see if the pitch continues to sway or not.

I would appreciate any input on the situation. Thanks

Darren
macd
hifimaniac
508 posts
 
Get a KAB speed strobe to dial in the speed. Do you use the SDS power with your VPI? This is a great upgrade if you don't and you won't have to check your speed to often.
ghostrider45
449 posts
 
Is perhaps the spindle hole slightly off center on the Ballads LP? That would generate the wow you're hearing and explain why your DSOM copy sounds OK.
chadlesko
94 posts
 
I second the KAB...but I don't think your issue is speed. Speed will change the pitch but that would be uniform throughout the record. If the record is "slipping", as in the drag of the needle is pulling the record at times, then a fluctuation in pitch will occur. My guess is that your record clamp needs to be tighter or the cartridge is tracking with too much force (most likely the 1st issue).

Spindle hole being off center would contribute...I agree with above...look at record for warp as well. Speed is very important for constant pitch...but not fluctuating pitches.
macd OP
103 posts
 
Hey guys

First I will say that I have an upgraded heavy weight screw clamp so I know its not that. I thought it was my belt for a bit so I boiled it and it shrank back down but did not help the problem.

What is interesting is the comment you two made about an off center pressing. The ballads lp is the most off center pressing in my collection and a bit warped to boot. (like a week old go figure). Anyways for some reason it never crossed my mind that it was the arm tracking horizontal that was making the wow.

Hifimaniac - How much increase in performance can one achieve with the SDS? Can upgrading the motor to a 300 rpm also result in better speed stability?

Thank you guys for clearing this issue up.
lewm
13,105 posts
 
The SDS will make your motor run a bit smoother and more quietly. It will also permit you to set the speed very precisely and stably. I found with a similar product, the Walker Audio Precision Motor Controller, that these effects also resulted in a remarkable "opening up" of the midrange, where I could much more easily separate instrumental and vocal lines. I think either device or an analogous one made by the tt manufacturer specifically for his motor is indispensible if you are running a belt-drive turntable. But as the others have said, the symptom you describe is most likely due to an off-center spindle hole. If it happened on every LP, and if you could actually SEE a speed variation using the KAB strobe or similar, I would suggest you have a defective motor or you need to replace your tt belt or tighten it.
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