[ACHiPo]

I was listening to a couple rock albums yesterday and they seemed a bit sluggish.  I recalled seeing an iPhone app that would measure RPM (Turntabulator--Pretty cool!), downloaded it and measured the speed.

Sure enough the platter speed is about 3% slow.  The speed measurement doesn't seem to depend on record/no record/stylus, but measures consistently 32.4 - 32.6 RPM.  Giving the belt a 1/2 twist didn't seem to make a difference, either.

Is there any way to adjust the speed of the motor?  Has anyone tried increasing the pulley diameter a bit?

Thanks,
AC

[Charisma12]

Your turntable has an AC motor which runs in cycle.  Therefore, speed cannot be adjusted.

But 3% variation is acceptable.  I believe human ears are not sensitive enough to detect that speed difference. 

[ACHiPo]

Your turntable has an AC motor which runs in cycle.  Therefore, speed cannot be adjusted.

But 3% variation is acceptable.  I believe human ears are not sensitive enough to detect that speed difference.

Charisma,
Thanks.  I may try wrapping string around the pulley to see if it makes an audible difference.  I noticed it on rock records that I know well, but it could be my imagination.

AC

[threadkiller]

It's been so long since I had mine, so things are foggy. Can't one move the motor to the left just a tad to change speed? I keep thinking that's how we did it, but I could be way wrong. Can you try a new belt? I think I'll go with that answer before I get gonged....

[ACHiPo]

It's been so long since I had mine, so things are foggy. Can't one move the motor to the left just a tad to change speed? I keep thinking that's how we did it, but I could be way wrong. Can you try a new belt? I think I'll go with that answer before I get gonged....

Threadkiller,
Moving the motor won't do anything I don't think.  A different belt might change things, but that's not a trivial undertaking.  The easiest reversable thing I came up with is to increase the size of the drive pulley by wrapping thread, Teflon tape, etc.  It will likely cause more problems with stability than it solves with pitch, but I'd like to know if I can even hear the difference in pitch.

Thanks,
AC

[SteevA]

A thicker belt will increase the speed as it effectively increases the pulley diameter.  It will also effectively increase the platter diameter buy not be the same ratio so this only takes a little off the gain at the motor pulley.

Steve

[threadkiller]

AC,
consider this for a moment.... With a Kuzma Stabi, one adjusts speed by where the motor is placed in conjunction with the Tbar chasis/bearing. One puts on the strobe disc and positions the motor for proper speed.
I know there's not a lot of play if your Ref has only the cutout hole and not the open slot, yet moving it a tad will effect speed. Are you using a strobe disc to measure speed? You should be.
And again, when I asked a few old buzzards who used to own Refs about this, they all said get a new belt, meaning yours is stretched.
Just thought I'd chime back in with my bag of nonsense.
Good luck!

[ACHiPo]

Threadkiller,
I'm not sure about the Kuzma-maybe moving the motor changes the load?  I can't imagine a geometry affect.

I'll try playing with the motor position.  I also have a new belt that I can try.

I'm using a cell phone app that appears to be quite precise.  I don't have a strobe disk, but can always pick one up.

Audiophile nervosa 

Thanks,
AC

[barrows]

Not necessarily a cheap fix, but there is one way to adjust TT speed for tables with synchronous AC motors.
The older PS Audio Power Plant AC regenerators feature adjustable AC frequency in 1 Hz increments.  One can probably find used units out there for not too much money.  Look for a P-300 or P-500 model (P-600 and P-1000 will work as well, but are much larger and more $).  These older units may need re-capping, but any competant electronics tech can handle that.

[sebrof]

I would either get a strobe or at least count and time the rpms. I would not trust the cell phone app.

[threadkiller]

I believe the apps are good. We've used them. I was only thinking strobe disc due to the Amadeus.
Can't vouch for your app, however.
You are incorrect about the Kuzma. One does indeed set speed by adjusting the motor position.
Try the new belt but first move your motor if you can.

[ACHiPo]

I believe the apps are good. We've used them. I was only thinking strobe disc due to the Amadeus.
Can't vouch for your app, however.
You are incorrect about the Kuzma. One does indeed set speed by adjusting the motor position.
Try the new belt but first move your motor if you can.

Will move the motor to see what happens, but there's only about 1/8" of play.  Belts for WTT Reference tables are rare as hen's teeth, so I don't think sourcing a thicker one is trivial.

[SteveFord]

An older electronics repair firm should be able to match up a thicker belt without too much trouble.  I know my now defunct local shop did that for me, no charge.

[threadkiller]

AC, an 1/8 of an inch can be huge for pitch variation. Get off your duff and experiment. Chop chop!
Also, you should be able to easily source a belt from www.turntablebasics.com, just in time to still play those holiday classics.... Good luck and happy holidays.

[ACHiPo]

AC, an 1/8 of an inch can be huge for pitch variation. Get off your duff and experiment. Chop chop!
Also, you should be able to easily source a belt from www.turntablebasics.com, just in time to still play those holiday classics.... Good luck and happy holidays.

Gotta get home first!  Just flew back from Japan, now off to Detroit to visit family.  Will be 12/23 before I'm back and able to experiment.

[ACHiPo]

AC, an 1/8 of an inch can be huge for pitch variation. Get off your duff and experiment. Chop chop!
Also, you should be able to easily source a belt from www.turntablebasics.com, just in time to still play those holiday classics.... Good luck and happy holidays.

Finally got around to doing some experimentin'...

Speed measurement std. deviation with the iphone app is + 0.15 RPM in quick mode, and about + 0.05 RPM in "exact" mode, so realistically a difference of ~ 0.2 RPM is significant.

Baseline (spinning, not playing a record) :  32.4 RPM 2.7% slow
Moving the motor 1/8" closer to the spindle--32.3 RPM (no difference)
Moving the motor 1/8" further from the spindle-- 32.4 RPM (no difference)

New belt (~0.030" thick vs. ~0.015" thick for the old belt):  34.1 RPM 2.4% fast 
New belt playing a record:  33.8 RPM 1.5% fast

I seem to be able to hear a difference between the two belts, less the pitch than the pace.  Regardless, both belts are within + 3% which the iPhone app rates at "good"