How to set SRA after determining true vertical?

Greg - good pictures! I think the high-mag one shows pretty conclusively that the groove undulations slant -- in this case toward the bottom of the picture (from bottom to top of the groove.)

Great pix!

If we imagine a line contact stylus trying to trace those modulations, if SRA is off then one end of the contact line will encounter each modulation before the other end. The stylus will shave across the modulation instead of tracing it precisely.

Mechanically (sonically) this will:
1) reduce stylus deflections (reduced micro-dynamics),
2) lengthen the time the contact line sees each modulation (temporal bloat),
3) alter the timing of when the stylus encounters multiple frequencies (loss of temporal focus and timbre) and,
4) alter the frequencies the stylus actually plays (FM distortion).

I hear #s 2 and 3 most easily. Paul is very sensitive to #1. He was able to adjust SRA on Cello's rig just by feeling the pressure waves coming off the woofers, without actually listening at all. Raul says he adjusts by listening to bass, so his sensitivity may be similar to Paul's.

P.S. Those records could use a good cleaning!

http://www.smartdev.com/LT/Align.htm. more drawings.

Dear Neil, Greg, Doug: This thread is really informative for all of us, unfortunatelly we can't do nothing different that what we all already do to set up the right SRA and as a fact we can't set up the correct SRA, our best is only an approach.

The main differences here are our ears frequency response at both extremes of the frequency range, our patience to setup the SRA on each record/track or to conform on an average figure, the accuracy of the RIAA eq. on our phonopreamp, the cartridges that we own ( stylus design ) and certainly our tonearms, our experience with live music and in the case of tube electronics: with which kind of " temper " wake up the tubes " that " day.

Regards and enjoy the music.
Raul.

See also, http://www.recordcollectorsguild.org