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Re: Cartridge alignment using DB Systems protractor.

Hi Mark,

I've assembled numerous links to cartridge alignment on our support page. Click the link below to get to that link-list.

The DB protractor has to be one of the most difficult ones I know of to use if you use both pieces. I gave mine to someone I didn't like. Seriously though, there are two problems with the DB. The first one is understanding how to use the frosted piece of plastic that sits on top of the actual protractor. The part you need is the opaque white piece with the grid lines and the two null points. Assuming that you were to figure out how to use both pieces, an even worse problem is the parallax induced by using the second piece. So, store the frosted part and use only the actual protractor part ... until you get around to purchasing a mirrored one from Turntable Basics that is.

It's useful to pick up a small magnifying glass, because you don't need a mirrored protractor in order to site down the cantilever - referencing the cantilever (and NOT the cartridge body) to the grid lines. A mirrored protractor like the one sold by Turntable Basics has the advantage of letting you know when you're not viewing the cartridge head-on, however. Do I have to mention that you need good lighting to do the job correctly? I'm amazed at how many people I visit who try to do the job with inadequate light. These are people with high dollar rigs.

Analogmaniac mentioned success with a Geo-disc. Protractors of this type require that you line up the protractor with a line running from the spindle to the bearing pivot of the arm. They are prone to operator error because it is quite difficult to do this accurately and reputably. Very slight rotational errors can result in overhang changes of a few millimeters. We're trying to get well within a fraction of the diameter of the bull's eye on the null point.

Analogmaniac may have developed a technique with this tool and I'd love him to share with us all, because conceptually it's a very good system if you can orient the protractor properly. A friend owns a similar, single point protractor. A while ago, and I played with it. The best I could do without complex machining or making up some kind of jig for the protractor was to stretch a piece of thread from the record spindle to the arm bearing. I tried to orient the protractor in plum with the thread but could not do this consistently, I repeat however, that if you can easily and repeataby orient this device it simplifies matters, but this is a big if. Some will tell you to shine a flashlight toward the bearing post and the light will reflect off of the high point. This may work on some tonearms.

Note that overhang and headshell offset angle (the cartridge twist) are interrelated parameters. If you check the link to the Chicago Audio Society in the links page below, follow that to the Linn LP12 FAQs (from Analog Addicts). Look at the overhang chart and which will help you to understand that relationship.

If you think about it, you'll arrive at the conclusion that you can effect a proper adjustment (cantilever parallel to grid lines at both null points) by changing only one parameter. Our armboards accomplish this by letting you fix the twist (offset angle) and change only the effective length (tonearm pivot to spindle distance). SME arms do the same thing by eliminating the headshell slots completely. The mounting holes are holes and not slots. Pivot to spindle distance is accomplished by moving the arm on a sliding track - changing the pivot to spindle distance.

What drives people crazy and prevents them from understanding a really simple concept is the fact that when you try to change only one parameter (let's say cartridge "twist"), you unavoidably also change the pivot to spindle distance slightly. I address this issue in great detail on our FAQ's page if your interested in reading further.

Cheers
Thom @ Galibier



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