The Placement of Tonearm Counterweights

This makes good sense. However varying mass v. distance on just one side of a conventional pivot arm has the limitation of a relatively small range of adjustment. To devise a "universal" arm with continuously variable effective vertical mass, I've been working on an approach that uses counterweights on both sides of the pivot of a short linear arm. So far this is doing a great job of optimizing set-up for cartridges of varying compliance. In fact, this adjustment is a very significant variable in accurate set-up, and the feature has vastly simplified the issue of cartridge/arm synergy.

Someting like the new Moerch arm Dave, ith counterweights to both sides and one in the rear?

Hi Bob,

The Moerch is certainly beautiful, and like other pivots does variable effective mass and other nice things with interchangeable armtubes. However I'm done with long resonant arm tubes and the inevitable junctions in wiring attendant to detachable wands.

http://cgim.audiogon.com/i/vs/i/f/1293020811.jpg

In addition to varying effective vertical mass the counterweights mass-load the point bearings.

Dgarretson
I am curious about some of your tone arm parameters. I am not suggesting that you are wrong I simply am an ignorant analog novice trying to learn something. Why can't the arm wands be effectively damped to stop resonance. Is it because damping materials used would be too heavy? Or do the laws of physics dictate that any length of a tubular structure will have a resonance frequency regardless of efforts to minimize its effects or to get it out of the audible spectrum?
How does the arm interact with the cartridge if the correct effect downforce and minimal restriction on the pivot point is observed such that the stylus compliance would be altered? I guess the mass of the arm restricticts it's motion to some extent but why would'nt the stylus be free to move as a function of its suspension?
I like linear arms BTW but never afforded anything beyond a number of ebay Technics TT in marginal condition.

I try for the simpliest approach that addresses the main problems of physics. The first principles are:

The ideal arm is such that on a flat LP, stylus deflection associated with normal tracking produces no vertical movement of the cartridge. (Horizontal movement is a necessity.) In this regard there is an optimal effective vertical arm mass (as well as a unique compression and rebound damping factor) associated with each unique cartridge compliance. This is because cartridge compliance is integral to the tonearm system that in aggregate controls tracking. From a practical viewpoint, continuously variable effective mass is the first order of business in matching an arm to a specific cartridge. Otherwise we are relegated to trial and error and the approximation of trying arms of generally "light", "medium", and "heavy" mass. This is expensive fun, but is unnecessary in view of the reasonable prospect of engineering an arm of continuously variable effective mass. Moveover, while reviewers like to say that a particular cartridge is fine with a particular arm, who really knows how good a particular cartridge can sound without an *exact* match to tonearm?

Assuming availability of an external mechanism to match tonearm effective mass to cartridge compliance, the ideal arm tube is infinitely rigid and weightless: a perfect conductor or absorber of residual cartridge vibration that does not reflect vibration back into the cartridge or itself add movement to the system. In this sense the optimal arm is no arm at all-- the shortest possible arm as available only in a linear tracker.

The rest of it can be dealt with in conventional terms. If the above problems are addressed, in the final analysis the only problem with a linear tracker is fluctuating geometry over warps. In a world of record clamps, vacuum hold-down, and periphery rings, this is an ancillary matter.