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In Reply to: RE: Happy Thanksgiving VPI ;-) posted by Mel on November 26, 2015 at 12:51:52
> Personally I prefer a "point to the pivot" type of protractor.
In my opinion, this type of protractor is the worst kind of protractor because it allows the greatest possibility for an erroneous alignment. It is virtually impossible to point the line exactly at the pivot and there is no way of confirming whether it's pointed accurately or not. Just the slightest pointing error will result in substantial null-point and overhang error without any way to double check the results.
The arc protractor, on the other hand, is the easiest to determine whether or not overhang is set correctly, especially when using a magnifying glass. Once the stylus traces the arc perfectly, you know beyond any shadow of a doubt that overhang is right on the button. Then you need only adjust offset to one of the two alignment grids. After that, you can easily recheck overhang to make sure the stylus still traces the arc exactly. The arc protractor provides complete assurance that your alignment is as accurate as humanly possible.
However, to each his own!
Happy Thanksgiving!
John Elison
Follow Ups:
Well, I've been pointing my Cart-a-lign to the pivot for many years without the problem John worries about. To make it, or a similar one like the Turntablebasics, even easier you can just tape some card stock to it and extend the pointing line to the pivot and then it wold be easy enough even for John to get exactly right. There are many other simple tricks.
As is said below, the Feikert type of protractor, or the VPI, easily allows for a perfect point. In the case of the VPI one it is just for their arms. Each of them could be improved, I think, with a mirror surface making it easier to align the cantilever.
John, I haven't the slightest doubt that with just a little practice you can do it, save yourself some money and be ready, without spending another dime, for that VPI 3D JMW arm attached to the VPI Prime that you covet.
> John, I haven't the slightest doubt that with just a little practice you can do it, save yourself some money...
I've done it and I fully understand the principle of the "point-to-the-pivot" type of protractor. However, my preference is for the arc protractor because it allows complete confirmation of the alignment. There are two null-point grids and the stylus/cantilever must line up at both simultaneously while holding the protractor stationary. You can also reconfirm overhang by rechecking that the stylus follows the arc exactly. I am fairly knowledgeable and experienced regarding cartridge alignment and I prefer the arc protractor over any other type of protractor I've used.
With regard to spending money, I prefer not to ! Therefore, I make my own arc protractors using Conrad Hoffman's Custom Arc Template Generator for Phono Cartridge Alignment . It is a free program you can download and it allows you to make sure the arc corresponds exactly with your tonearm's pivot-to-spindle mounting distance.
To each his own!
Best regards,
John Elison
thank you john e. for your suggestion about the printable protractors. i had a problem with my main cartridge the other day and put my back up zu denon on the arm, but in the past have had a feikert on long term loan that is now gone. i ordered a new one, but it won't be in until next week. so, in the meantime, i printed one for my arm and used it on my zu. the zu, like all denons is very hard to align because the stylus sits so far under the body, but with an old radio shack helping hands and bright flash light, i managed. the music was sorted out better and the bass tighter, so an improvement over eyeballing. luckily, from use of the past feikert, i knew the spindle to pivot distance was 299 mm. once you have that number, the program is simple. thanks again.
Tom Collins
You're Welcome!
One thing you should be aware of when using Feickert's Protractor is that the two alignment null-point grids are offset from each other by a fixed angle. This angle corresponds to one specific effective length tonearm only. Therefore, unless your particular tonearm has the unique effective length corresponding to Feickert's null-point grid offset angle, you will need to reposition the protractor when checking between Step 2 and Step 3. In other words, Feickert's protractor is not an arc protractor although the alignment grids are laid out on an arc. That arc will be valid for one specific length tonearm only. Consequently, after setting cartridge offset at Step 2, it is perfectly okay to reposition the protractor when rechecking cartridge offset at Step 3.
I couldn't find any mention of the actual null-point radii used by Feickert's Universal Protractor. Normally, when we think of Baerwald (Lofgren A) we think of null-points of 66-mm and 120.9-mm, but those are only valid for the IEC modulated groove envelope with innermost groove at 60.325-mm and outermost groove at 146.05-mm. You might want to measure the distance on Feickert's protractor from the spindle hole to the "B" null-point lines at Step 2 and Step 3 just to confirm the null points are in fact 66-mm and 120.9-mm.
Anyway, it will be interesting to find out how closely the alignment achieved with Feickert's protractor corresponds with Conrad Hoffman's arc protractor.
Good luck,
John Elison
Yes. I was thinking the same. Could send it back I suppose.
Tom Collins
the Feikert works very well and is easy to set up to assure accuracy.
Tom Collins
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