Linear tracking tonearms.....

Does anyone know how changes in SRA/VTA effect overhang with the Schroeder LT arm? Overhang should be zero with linear tracking tonearms because they precisely trace the LP radius to the spindle. (I think the Schroeder traces many different radii toward the spindle, always maintaining tangency).

But changes in SRA/VTA effects overhang on pivoting arms and if the linear arms have no way to adjust overhang, then if it changes, the stylus would be tracing a line parallel to the LP radius but offset slightly which should produce tracking distortion.

I ask because I do not fully understand the mechanics of linear tracking arms.

Overhang has little to do with SRA/VTA. Linear arm can adjust overhang/underhang to zero too.

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Peterayer, awhile back I queried AA on this point w/r to my Trans-Fi linear arm. Bottom line is that with a linear arm small shifts off zenith are audible at degrees of error that are well below a conventional pivot arm across the arc of an LP.

http://db.audioasylum.com/mhtml/m.html?forum=vinyl&n=1010331&highlight=Dave+Garretson&search_url=%2Fcgi%2Fsearch.mpl%3Fsearchtext%3Djmlab%26SelectForumcables%3Dcables

In this thread John Elison posts graphic representations of errors induced by minute variations off perfect zenith. Any good linear arm should allow readjustment of overhang after a change in VTA.

Peter, Most linear tracking arms I've seen have slotted head shells. So they can be adjusted to compensate mis-alignment by other adjustments, like VTA, and VTF. Most have a protractor with a straight line (instead of an arc), with lines that are 90 degrees off the main line to line up the cantilever (zenith).

One exception is the Thales Simplicity. With the design of the Simplicity you would have to take the head shell off, to align it, in it's jig. This is not ideal because you can not align the stylus with a load on the suspension. Since we know that different VTF will change the alignment (overhang), there is no way to know for sure if it's perfect or not.

As said above, if the alignment is off on a linear tracker the zenith will be off a little all the way across the record. Not sure how audible that is but I will look at Dgarretson's link about that.

Even though the Thales Simplicity is a pivoting tangential tracker with its own idiosyncrasy, you can still align it using traditional methods. You can use a typical paper template or protractor to confirm alignment. Since there's no overhang and supposed to be tangent, then wherever the stylus on the template the cantilever should be 90 degree pointing to the spindle. Typical template has two points on the arc, inner groove and outer groove. Draw additional lines on the template to confirm you have more than just two points are tangent.

You can draw your own template: find the effective length (Thales published a nondescript "9 inch") which should be the distance between the left armwand's headshell pivot to armbase pivot, and draw an arc from base pivot to spindle and draw multiple lines intersect with the arc and then draw perpendicular lines double distance all the way back to the Thales triangle. Voila, you have yourself a template you can use to confirm alignment. This way, you don't have to blindly follow the headshell alignment jig.

Bottom line is to have the cantilever always perpendicular (90°) to the radius or pointing to the spindle. In a traditional pivot arm, you only have two tangent points but the Simplicity is tangent on every point.

See GIF so you get an idea.

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