My thoughts on VTA is that you are actually looking to get stylus rake angle correct. You find the figure from the manufacturer and then look to hit that. Now some folks use USB microscopes and superimpose a compass over it to get the measurement down pat. I am not that sophisticated. I use magnification and good light to get the diamond leading edge to 90 degrees, and then adjust by ear from there. With on the fly VTA its pretty easy to do, so I don't get worked up over the USB scope thing. Of course it depends on the diamond profile, some are more finicky than others. Now some cartridge manufacturers build proper VTA indicators into their cartridge design, such as a parallel bottom, or Ortofon wants their logo parallel to the record. Those are ways to rough it in, and then you can adjust by ear from there. Just the way I look at VTA, and my opinion is all.
Advice on setting VTA
I have set it before, but not exactly certain if I’m going about it the right way. I am generally setting it by eye, eyeballing the botton of cartridge body to get it as parallel as possible, sometimes using a 3x magnifier to assist. I have also in the past used playing cards as a reference for some cartridges, so I have something to fall back on. Generally using the cards stacked at the tonearm base, similar to using feeler gauges. I’ve read that using an index card on top of record can be a good way to set it due to the parallel lines on the card. My question is what am looking at to get parallel? The bottom of tonearm, top, or the bottom of cartridge? The tone arm is a carbon fiber/aluminum 9 inch pro-ject. It does appear to have a slight taper towards the headshell end of arm.