Decca London Super Gold Compatibility Question

@noromance, you make a good point. A heavier counterweight closer to the bearings can produce the same effective mass as a lighter one further away, plus create less moment-of-inertia, a good thing say engineers (I take their word for it ;-). The Zeta arm has a counterweight that has it’s rear plate bolted on, with two internal steel washers which can be added or subtracted as needed or desired. Mine was missing one of the washers, so I substituted lead weights bought at a hobby store.

I needed the extra mass to compensate for 1- the missing Zeta counterweight washer, 2- the extra mass of the Decapod on my London Super Gold Mk.7 (it doesn’t weight much more than the standard mount), and 3- the outrigger that is integral to the Townshend Audio Rock Elite table I have the arm mounted on; it gets bolted on to the cartridge end of the arm. The Rock/Zeta/Decca-London combination, a true classic!

As stiff an armtube as possible benefits ALL cartridges, but the Decca/Londons, having no rubber damping suspension (and no traditional cantilever; the stylus is attached to a V-shaped metal plate, which goes straight up into the cartridge) benefit most of all. The D/L’s transmit a LOT of mechanical energy into the arm, exacerbating any armtube flex and/or bearing "rattle" present in any given arm. The Zeta is known specifically for its’ strengths in those two criteria.

The front-end damping provided by the Townshend Rock is exactly what makes that table so appropriate for use with Decca/Londons. A damped arm has long been recommended for use with the cartridge, and I have had a few; the Decca International, the Mayware Formula 4, and a modified (with damped bearings) SME 3009 Improved. The Rock makes a damped arm unnecessary (and in fact the front-end damping afforded by that table is a better way to damp than applying it at the back end of the arm), allowing armtube stiffness and superior bearing design & build to be prioritized. The Rock comes with a metal arm mounting plate drilled for the Linn/Zeta arms, which share the same pivot-to-stylus distance. The plate even has the six holes required by the Zeta’s arm mounting collar---very handy. I added a layer of thick acrylic under the metal plate, as that plate is a little too ’lively" for my liking. Yes, I believe in damping resonances!