Parallel? How do you set the VTA?

Happily my ear tells me when the setting is off, but as a base, how do you determine conclusively your tonearm is parallel?

Why should I want to? You said it yourself, this parameter is best adjusted by ear. Visual settings like "tonearm parallel" are mere approximations, someplace to begin the listening from.

With respect, a quest to "determine" the position of a mere approximation "conclusively" is nonsensical. I can level a cartridge or tonearm by eye in about 15 seconds. Then, whilst you're fussing with spirit levels, printed cards, magnifiers and other distractions, I'll have dialed in the optimal SRA by ear and be enjoying the music.

"...some of us just don't have the same acute hearing that you do."

But, Actusreus, read your own OP (that I quoted). You've already said that you DO hear the difference.

You don't need more acute hearing, you've already got it. You just need the self confidence to trust it. More time listening, less time measuring. :-)

Dover,

I've been doing exactly that for 10 years, except that I've no need for calipers. The height adjustment scale on my tonearm provides precisely repeatable settings.

The optimal arm height for each LP is recorded on a sticky note on the record jacket (and updated if I change cartridges). Setting arm height for a re-play takes only seconds.

Set and forget? Nope. Set and remember works better for me.

Zenblaster wrote, "I have to admit that after initial set-up I only change vta when something doesn't sound right."

Oddly enough, that's also why Paul and I adjust for each LP. It's not about measurements or theory. We adjust because if we don't, it doesn't sound right.

I could describe in excruciating detail but that would make it seem much harder than it is. As Raul kindly noted, the actual doing typically takes just a few seconds.

That's us... may not be you. As Jazdoc said, whatever works for your ears and priorities is best, so apologies to Actusreus if I pooh-poohed his preference for an objective baseline position. Each to his own.

"...if Dover can hear a change of 0.00635 degrees in the SRA, a change of a fraction of degree in the ambient temperature would result in a change in the sound that he could hear.

Very true. During Raul's visit (several years ago) we played music for several hours, then broke for dinner. The setup was well dialed in when we stopped, but on re-starting 45 minutes later the music sounded flat, dull, lifeless.

All electronics had been left powered up, but I realized that the cartridge must have cooled down from non-use (it was December and COLD outside). I tweaked VTF up a tiny bit.

BANG! Dynamics, pace and jump returned in spades, instantly. Raul asked what I'd done, the adjustment was so quick and tiny he couldn't see from the sofa. I demonstrated. All I'd done was nudge one of the O-rings on my arm stub inward by less than its own thickness, a VTF increase of much less than .01g. I went back and forth a couple times and the sound alternated accordingly.

Some setups are indeed that touchy.