Turntable speed accuracy

Your 60Hz line freq, may no longer be sacred! This COULD POSSIBLY become an issue soon. A copy/paste, from a previous thread: Something that got me thinking more about speed accuracy lately, as both of my tables are equipped with AC synchronous motors: (http://wattsupwiththat.com/2011/06/25/it-hertz-when-you-do-that-power-grid-to-stop-regulating-60-hz-frequency/) (http://radiomagonline.com/infrastructure/power/60hz-stability-going-away-0627/) If you are using a strobe disc, that depends on your house lighting's 60Hz flicker, or your table has a motor, dependent on your AC's 60Hz for speed regulation; take note. This may soon become a concern. (Note: They were NOT simply referring to the nightime correction, in these articles)

when i compare various turntables to the same recording on my Studer A820 it's easy to hear which turntables get the closest to matching the soliditiy of the music on the Studer.

Nojima Plays Listz is a very good recording of Piano on Lp, and is a Tape Project tape too; in theory the solidity and speed accuracy of that tape is the reference for the Lp as we know it's the actual source. on that recording there is no place to hide any speed variations as well as inaccuracies. and there are plenty of peaks to hear also.

i do have the KAB strobe and use it. however, it's limitation is the accuracy of the printed strobe and the perfection of the center hole of the strobe.

i think the tape-Lp comparison has more value to me.

Palasr wrote: "While frequency accuracy (and adjustablity) is one issue, it doesn't begin to address waveform shape, harmonic distortion, phase amplitude and shift, and all the other interesting things that go into generating a waveform suitable for driving a synchronous AC motor."

I have a Mark Kelly AC-1 drive controller on my VPI TNT that features separate manipulation of several of these parameters, while deriving an AC waveform from a 12V battery independent of the power grid. Unlike a VPI SDS, the AC-1 is a true two-phase controller-- it eliminates the phasing capacitor from the motor tower. Varying the separate effects independent of frequency is easily audible, as are differences between belts of varying compliance-- yet the strobe disk doesn't move a whit.

No one seems to set the speed as I do. I adjust speed while playing same known track on CD as well as TT. I measure with stopwatch and play simultaneously going back and forth such that the song start and ends at exactly the same time on both CD and TT. I change source back and forth, each note sounding exactly same that you can hardly tell diff. It helps that my main CD source and TT are set pretty much to same tonal balance. It takes few iterations, but then I listen without worrying about speed. Makes sense?

Don, I think you underestimate the situation.

"Speed variation "is" noticeable on classical piano "IF" you have played a piano, but typically the audience could care less. "

I cannot play piano, or any other instrument, or read music. I'm certain I do not possess perfect pitch. But when I listen to piano recordings I am quickly aware if the sound becomes either sour or cartoonish. That tells me something slowed down or sped up. It could be my turntable, it could be the power line, it could be someplace in the recording chain. But it is not difficult to hear when a recording does not sound like a live instrument. (And yes I understand there are multiple other factors in the "sounds live" experience.)