So the proof of concept worked, with attractive forces. In the first video below, you will notice how quickly the arm stabilizes; and without the mod, the arm would constantly wobble even worse with every LP all throughout the playback.
I used two
3mmx1.5mm (3/16" x 1/16") Neodymium N52 magnets in the arm and five layers of
mu-metal tape that I use throughout for shielding, about 0.5mm total thickness. Any thicker and one of the sides would win and the arm would tilt permanently. Mu-metal is ever so slightly magnetic, unlike metallic rings that I also tried, and perfect for this application. The magnets are temporarily attached with blu-tack.
Here's is a video of the arm tower's underside with the mini magnets:
I can tell you, I have never seen this arm so stable before, LP after LP.
And a whole bunch of magnet sizes I had in hand to try:
The way the magnets are attached - perfectly along the horizontal pivot axis (but obviously away from it) - has had a very minimal impact on the tracking force, from about 2.250g to roughly 2.270g, really negligible, and closer really to the 2.3g I want to use on this cartridge, anyway.
Next, now that I know where the magnets need to go, I can order a custom ring magnet from K&J Magnetics (roughly 31cm in diameter) to replace the mu-metal, for repulsive-type stabilization, which should be a lot better still. And now I know it has to have a very weak magnetic field.
Listening impressions are underway, and for sure, substantial improvement in imaging, with sharper portrayal of instruments.
Finally, since I am into tweaking lately, if you are seriously into espresso making at home, here's the La Marzocco Strada 58mm non-pressurized (of course) basket I got for $30, and they have gone to extremes to make sure hole-size variations are extremely tight, and even include a histogram of the hole distributions of this very basket and an image of it - we are talking audiophile extremes here:
I hope you also enjoyed the 1kHz test tone - very stable, pun intended.
-ack