Halcro
Your DD has stylus drag as well. The only difference is that it is dealt with by the speed servos. Some belt drives have servos, some have self correcting AC motor controllers.
One could argue that the speed correction for the stylus drag in a direct drive is always working - to what effect on the music ??
In Peterayer's example he could correct the stylus drag at the begining of the record, and then any inherent problems of active speed correction are avoided.
In Peterayers example, the speed error after adjusting for stylus drag at the outset, is the VARIATION between maximum and minimum stylus drag incurred by the stylus tracking the record playing. This will be a small %age of 0.003.
In Peterayers video the record does not appear to be flat - the shadows move up and down on the record. Testing by both Bruce Thigpen with his ET tonearms and the Shure white papers on low frequency resonance confirm the existance of stylus "scrubbing" from imperfections in the groove, even apparently flat records, that cause mistracking and WOW. Shure claim resonant peaks of up to 20db, equating to 10 times increases in motion. The timing errors from this artefact would probably dwarf a timing error of a %age of 0.003.
So its all a bit nebulous really. Consistency is probably the greater virtue in terms of speed accuracy once you get a this level.
I would guess many audiophiles cant hear a speed error of that magnitude, but they are more likely to here WOW on a piano or acoustical guitar note. There are many other factors - my perception is that vacuum hold down greatly improves piano stability as does a tangential tracking tonearm - so if you are looking for perfection in timing there may be bigger gains elsewhere than chasing down a %age of 0.003.
