Many watchers here will be aware that I have a bit of a bugbear with the arm mounting collar for my Jelco SA-750D. Specifically, there is vertical wobble of the arm pillar that can (and does) result in quite significant azimuth errors as the arm tracks the record. The fault lies in the design of the Jelco collar, which has an undersize hemispherical cutout to one side of the pillar hole, which should ensure that the arm pillar fits snugly and vertically, when pressed against this cutout. This is very similar to the design of my Ittok LVII's collar, but in the case of the Linn it works faultlessly, every time, because the securing grub screw is more or less in the middle of the collar (heightwise); in the Jelco collar, the grub screw is tiny and located right at the top, so it pushes the pillar over at the top, rather than pushing the whole thing against the cutout. Setting the arm up with the Jelco collar is impossible without the aid of a headshell spirit level; and even then the silly small screw has to be overtightened against the soft alloy of the arm pillar. The collar is a hateful piece of design that is quite at odds with the good engineering of the rest of the arm. So, the only thing to do was to have a new collar made up along more sensible design principles. Here it is:



The top (visible) part of the collar is 5mm taller to allow the set screw to be located as far from the top as possible; also that screw is now M6 with a nylon stub at the end. The hole in the pillar does not have a cutout, but it is just the right size for the arm pillar to move up and down freely with virtually no movement in any other plane. The bottom part of the collar has been extended to give as much support below as possible (slightly too far, as it happens, which would be a problem with a Neglex cable rather than my Audio Origami/Cardas one). Otherwise it's a drop-in replacement for the Jelco collar.

Setting up the arm is now a breeze - there is absolutely no movement other than up and down, and azimuth is consistent across the record. The grub screw can be just 'nipped up' or cranked tight without it digging into the arm pillar. As a design exercise this has been a great success, at modest cost. The collar that you see above has been bead-blasted but not anodised, but the quality of machining and finish is exceptional. As I sit here typing, the Kenwood is sounding very good indeed. It did before, but required a great deal of faffing around to get the proper setup - now it's as fit-and-forget as I could have wished. I'm very pleased!