What defines a good tonearm

But it is the stylus tip that follows the groove, not the tonearm. If the pivot is not fixed, then energy transmitted to the stylus tip by the undulations of the groove wall, which is "music", can be lost via "wiggling". Ideally, the arm wand should be fixed in space at its distal end, IMO. Anyway, the point is moot where the very best unipivots are concerned, like the Talea, which blew me away at a local friend's house.

Mikelavigne: "the very best arms i have heard are the Durand Talea 1 and Talea 2 in my system, in other systems, and at shows. i would also add the Continuum Cobra to these 2."

Not to be nitpicking but I just want to point out the Cobra is not really a traditional unipivot because it has a secondary pivot/ball bearing, a sapphire "swash plate" that supports the second spike, much like a training wheel on a kiddie bike. Overall, it has TWO contact points, unlike a traditional UNI-pivot design. The Talea, from my own understanding, does not have a secondary bearing. The Cobra has no azimuth rocking at all. It belongs to a genre that includes tonearm like the Basis Vector, Continuum Copperhead, Graham Phantom, Nottingham Space arm, Holborne, SPJ, and perhaps precious few others. The Graham's secondary bearing is magnetically supported so it's compliant system which is a subgenre within a genre. If you think about it, this group of tonearms are closer in concept to DUAL pivot design like some knife edge bearing arms like old SME and SAEC, or dual spike arms like higher models from Origin Live--essentially two points sitting on a horizontal ball bearing. The Cobra and others are really a hybrid between pure uni-pivot and dual-pivot. A 1.5 pivot?? :)

Oh, the Simon Yorke tonearm uses a teflon sleeve over the bearing post acting as the secondary bearing but does not even use a ball bearing. Very unique and brilliantly simple.

It's debated among designers whether having some compliance or "wiggle" room in azimuth motion is a good thing. Basis' Conti argues that's not a good thing, hence his Vector design. But a rigid coupling is adding and extra contact point is not a good thing to Bob Graham. Which one is better is up to the user to decide but I sure enjoy the choices we can make. Personally, it's fun for me to think about these things and I have dog in this fight. Tonearm theories are so fun! I hope over time we will have enough data from users in the future to describe these tonearms' sonic traits relating to their designs.

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Dear Hiho: You are right, the majority are dual points. The first two points design I know was the one from Audiocraft 3300/4400 from what born the Graham.

All what " surrounded " a cartridge playback is so imperfect that an unipivot ( true one. ) design can't hyandle. We have to think on the forces around LP off center holes along non flat records along what the stylus tip has to negociate on the grooves. A unipivot design is at mercy of all those imperfections along the tracking tip forces that due to its inherent unstability preclude as a " best " bearing choice. This not means it can't works because we have several examples that said it works but the penalties are additional distortions that a fixed bearing ones does not have because that regards.

The cartridge needs at least in the tonearm: stability, dead stability because it is surrounded for to many unstabilities elsewhere.

What like we at home?, IMHO it depends on what kind and level of distortions we accept, which kind of trade-offs we are willing to accept.
Of course that some way or the other we have to have an objective method/process to be aware of different kind of distortions and different level of those distortions.
Many of us are not aware of those distortions and like what we are hearing with out note that what we are hearing is full of distortions.

As I said I prefer a fixed bearing pivoted tonearm against an unipivot but this is me.

My take is that whatever happen between the stylus tip, grooves and record and recording imperfections the tonearm task is to stay steady and neutral to those " movements " adding nothing that put additional " problems " to the cartridge very hard task.

Lewm, lowering by design thgose unipivots issues does not menas disappeared or that has no influence, its means only that the problems are only a little better under " control " but its influence is always there.

The fixed bearing design is perfect?, certainly not nothing is perfect but is more cartridge's friendly and this fact makes an overall difference everything the same.

Regards and enjoy the music,
Raul.

I meant to say "it's fun for me to think about these things and I DON'T have dog in this fight." I apologize for all the bad spellings and syntax.

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Dear Hiho, I was looking for your dog. Thanks. But be careful using the word "syntax", or you will conjure up Syntax himself, that man of mystery.