setting VTF with a digital guage

Offsets using VTA tower on this thread

http://forum.audiogon.com/cgi-bin/fr.pl?eanlg&1366675416&openfrom&13&4#13

Andy,
One thing to keep in mind is that with the Classic tonearm, the VTF decreases as the tonearm gets closer to the platter level so you do want to make sure the VTF is measured at the record surface level. The scale you have gets pretty close, but is still a bit too high to give you a precise reading. I purchased a digital scale from ebay (APTP445) that has a relatively big, flat measuring surface and I built a step with a bent credit card to measure the VTF precisely at the record surface level. It did make a difference compared to the type of scale you have. So to answer your question, yes I do measure the VTF level with the playing surface and it is critical to do so, especially if your cartridge is designed to perform optimally withing a narrow range as my Delos. .

There appears to be a belief that VTF doesn't vary across the record and that checking it at one point is all that is necessary. Depending on the table and arm, I've found that this is not necessarily the case. So what do you do? Try to check all across the record and determine an average. At least that's what I've been doing.

Andy, you might try experimenting by measuring the differences in VTF between the gauge and your setup LP to develop a calibration adjustment that you can apply when using the Acoustech gauge on the platter.

Start by figuring out how much higher above the platter the gauge surface is than the LP you're using to set VTF. You could set the gauge on a flat surface and place an LP (or LPs) next to it until the heights are the same. For reference, here are the measurements I've compiled from some posts I've read...

Hgt(mm)-Wgt(g)
1.00 - 100
1.27 - 120
1.52 - 150
1.77 - 180
2.02 - 200

Then, with the gauge on the platter, set your tonearm and cartridge combination to 2.00g of VTF.

Without adjusting the counterweight, place the LP(s) on the platter equal to the height difference you measured and record (and average) the VTF.

You now have the difference in VTF readings between the gauge sitting on the platter surface and your setup LP.

You'll then have a calibration factor that you can apply to the VTF measurements you get with the gauge on the platter. For example, if the VTF difference you recorded was 0.1g higher (the readings averaged 2.1g) you actually set VTF 0.1g lower to get the VTF you're after.

If you're really motivated, you could record measurements for a few different thicknesses to see if the relationship is linear or curvilinear, but I'm not sure that's necessary.

You can protect the surfaces of the albums by using thin sheets of paper.

Regards,
Tom