Speed Stability

I noticed while playing records over the past week that the European and Asian pressings seem to be punched true-ie. no visible swaying of my tonearm. US pressings however, seem to be a mixed bag. Some records are true and some I see the tonearm swaying quite a bit. Still, with the exception of the pure test tone section of my test record, I cannot hear the runout in the music.

Jeff L,
We didn't take any photos. You might find them online somewhere. Remember I was talking about RMAF 2008, not 2009.

Tony,
Further to what Mosin said, speed variations occur over every possible time span, from the length of an entire LP side to a nano-second or less. A strobe will usefully measure variation that occur over longer times, but becomes less useful (and eventually useless) in measuring variations of shorter duration.

The particular time-domain errors we listened for (and did not hear) on Mosin's Saskia table at RMAF are far too short-lived to be evidenced by any strobe device I've seen. A signal analyzer would reveal them but a strobe's resolution is far too coarse.

More fat to chew...

Then it would stand to reason that the position of the record relative to the platter can affect playback quality. What I mean is, if the turntable has a certain rhythm (wow and flutter characteristics) then it must be possible to turn the record relative to the platter, ie say in 10-15 degree increments and effectively match, or optimize the record's eccentric hole tolerances to your turntable and find the best playback position. Sounds like an interesting experiment. Has anyone tried this?

Very true. Eccentric rotation alternately accelerates and decelerates the velocity of the groove past the stylus. Varying groove velocities necessarily cause pitch variations, think Doppler effect. These variations may or may not be audible depending on their severity, the qualities of the whole system and the acuity of the listener.

Rotational eccentricity also alters the balance of lateral pressures between stylus and the two groovewalls. This will affect channel balance and crosstalk and may impair clean tracking.

If a TT has an eccentric spindle or platter, the solution clearly is to repair or replace that table. Mounting LP's off-center just to fix an eccentric table would be the worst sort of band-aiding. (Sorry if I misunderstood, but that's what I thought you suggested.)

OTOH, if you're asking about off-center record holes as the cause of speed variations, Nakamichi used to make a table with an eccentric/adjustable spindle to compensate for this. Pretty complex, pretty expensive, no longer available new. I never used one and don't know of any other tables which address this.

Simpler just to ream out the record's center hole and clamp it in place at the appropriate rotational position to get it centered.

We are well beyond eccentric platters here. The experiment is based upon matching the noticeable to unnoticeable eccentricity of the source (the record) to the wow and flutter and surely the unmeasurable runout of the turntable platter. The theory is that a record should sound better at the optimum position relative to the platter. Has anyone ever noticed that sometimes a record sounds really good and at other times just so so? Could it be related to the record's random placement on the platter?