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.
actusreus
200x usb microscopes with a focusing rail can be bought on ebay for less than $100. It takes some practice to get a serviceable image with a horizontal reference, but once obtained, you then overlay the image with protractor software to measure the stylus rack angle. Adjust the sra at the pivot point to obtain the recommended 92 degree sra. If you change the VTF, you will need to adjust the sra as the cantilever will flex thus changing the angle.
Get a Graham Phantom Supreme and your worries about consistently setting the correct VTA in seconds for every record thickness is over. The bubble level built into the pivot tower makes all the difference. Too bad other tonearm manufacturers don't get with the program by incorporating a level in their designs.
+1 Rockitman. I've thought the same thing ever since the Graham hit the market.
Brf, the USB microscope is a great tool as well for sure, and is on my to-buy list. I like some of the DinoLite models with measuring software, but they are around $300 so the purchase will have to wait.
I have a screw gauge that slips under the arm lift.
1/4 turn of the screw equates to 1/1000 of an inch.
I can hear 1/1000 of an inch like night and day.
In reality you are only getting near the zone with bubble levels.

But then what about the cutterhead angle, which varies by record.
So the only way is to listen and dial in each record and using dial calipers to measure and record the height for each record.

Any takers ?
Dear Frogman: Of course and agree with you: what will define where the tonearm will be parallel or not is at wich VTA/SRA the cartridge signal quality performance is the " best ".

Now, due that the analog medium/LP is so imperfect that VTA/SRA is changing every groove on playback as is changing VTF and overhang too.

That Fremer 92 degrees could means almost nothing because that could be only in theory but on playback always is changing. Ok, could be a point to start but nothing to " die for ".

My advise is to have 6-7 differnt LPs that we know in deep and that can help us as a testing tools to the cartridge/tonearm overall set up. These works have to be make it by ears. At the end our cartridge SRA set up can coincide with those 92 degrees but it is not important that that happen but that what we are hearing LP after LP has the best quality performance we can achieve in our audio system.

Unfortunatelly because the whole analog imperfections medium many subjects that gives us the theory can't be achieved during LP playback.

Regards and enjoy the music,
R.