[W9TR]

This is a really interesting topic. I’ve used the Rabco arm and still have a B&O 4004 linear tracker but my 12” unipivot is working really well and sounds great......but I always liked the concept of linear tracking arms.

I’m very interested in your comparisons of the two!

Linear trackers theoretically eliminate the geometry problems of a pivoted arm which is only correct at the two null points and there is a lot of religion around which is the best geometry.

Linear arms eliminate this problem and also eliminate the offset angle and by doing so eliminate skating forces. That’s pretty neat.

However they raise their own set of problems. The short arm tube of a linear tracker has much higher sensitivity to changes in record thickness and resulting changes in VTA.

Most linear tracking arms have significantly higher mass in the horizontal plane than regular pivoting arms, and different mass in the horizontal and vertical planes. So compatibility with the compliance of some cartridges could be an issue. This greater horizontal mass can also mean greater deflection of the cartridge’s cantilever. Again, some cartridges will handle this better than others. The servo system used by B&O and others eliminates this issue to a great degree.

One thing I noticed with the Rabco and B&O arms is the record sounds the same at the beginning, middle, and end.

Tom