This is a very good question. You simply cannot adjust it with the eyeball method.... The playing card method might be good but only providing your arm has absolutely no taper to it. The only arm that I have used that makes this adjustment easy is the SME...with a horizontal line printed on its side..however adjusting its VTA is more difficult than others. In the end..the ear is the final arbiter, however I think tonearm setup is unduly difficult. Each arm has its own tricks, but I don't think any of them is easy.
Parallel? How do you set the VTA?
Silly question, but how do you guys determine whether your tonearm is parallel to the record surface? I had my tonearm set up happily for months, but recently started messing around with the cartridge alignment and the VTA, and I'll be damned, but the folded index card method gets me nowhere now. Even with adjustments I keep getting the same visual effect. Happily my ear tells me when the setting is off, but as a base, how do you determine conclusively your tonearm is parallel? For reference, I have a VPI Classic. Thanks.