Servo Controlled Arm

Heh! If avoiding skipping were the only criterion for tonearm performance, virtually every tonearm would be a contender. ;-)

The theoretical problem with servo control of a tangential tracking arm is that, by definition, correction doesn't kick in until the arm is OUT of tangency. Also, depending on the design, the drive may then scoot the arm right past the tangency point until it's off in the opposite direction.

How far out of tangency any particular servo-driven arm gets before correcting, and how far it overshoots, depends on design and build quality. But any servo controlled arm must always be hunting for (and may rarely find) the true tangency point.

Throw in variable groove spacing and off-center LPs that can send the tangency point rapidly forward or even backwards, and true tangency may be an infrequent event at best. A good pivoting arm may actually cope with these challenges better.

The inherent impossibility of maintaining tangency theoretically limits servo designs to less than high end performance levels. Whether any non-tangencies will actually be audible depends on the resolution of the system and the ears of the listener, so YMMV - as usual.

Sorry to the OP for my generic response, not related to his arm. I read "servo controlled" and assumed we were discussing a linear tracker. "Servo dampened" would have clued me in to googling first. Thanks to Hiho and Kirkus for addressing the real question.

I also wonder how an active servo mechanism could respond effectively to the varying resonance damping characteristics of different cartridge suspensions. Every adjustment it would make would be after the event.

A servo could be adjusted to control horizontal and lateral resonance frequencies of the whole arm, but that doesn't address the real challenge in cartridge/tonearm interaction - controlling internal resonances that feed back into the cartridge and alter the signal it generates.

The internal energies in a cartridge/tonearm occur at all sonic frequencies and with constantly varying amplitudes, all at the speed of sound. Quite a challenge for an active system to deal with.