Unipivot tone arms

I’ve had a Moerch UP-4 on my Scheu Premiere MKII for 20+ yrs.

Used with a couple Ortofons and Lyras…setup is currently in my A/V system (not main) but works and sounds great.

Have also heard and operated (not my own) VPI unis with ZYX and Lyras.  Work and sound just fine.

Most modern (meaning brought to market within the last 10-20 years) unipivots are not really unipivots in the original sense of the term, because most manufacturers have modified their unipivot designs to reduce or eliminate their capacity to rotate in the plane of the pivot, which makes the azimuth unstable. These modified Unipivots are also made less prone to "chatter" at the bearing point, by use of magnets, etc. As a result, the better modern unipivot tonearms, like the Kuzma 4-point or the Graham or a VPI with their add-on modification, are really excellent tonearms, but expensive.

One of my favorite turntables was an LP-12 I got used in 1975.  This was before they added electronics to it…just a Scottish AR or TD150.  My roommate was in the UK on a fellowship so I asked him to bring me a Keith Monks arm for it.  I mounted it with a Sonus Blue Label I selected from our store inventory as having the straightest cantilever, and used it with an ARC SP-3a, a Dyna PAT-5 and a DB Systems 1A until our home was burglarized. All that remained of it were the little dusty blobs of liquid Hg on the floor!

The KMAL unipivot was silicone damped, so its rocking motion was not readily apparent. The arm wiring ran through 4 baths of liquid mercury in lieu of copper wire to eliminate, not merely reduce, any torque effects on the stylus. 

Long-time unipivot user here, starting with a Magnepan Unitrac I way back in the day. Having compared current top-end unipivots such as the Graham Phantom and Reed 3P against SME and Tri-Planar on identical tables, I can opine with some confidence that the perception of a difference in sound, quality, tracking ability and so forth is entirely psychological.

Not only has no one been able to traceably document bonafide differences in channel separation, azimuth accuracy, anti-skate "error" or compliance. Manufacturers wouldn’t still be making both bearing and unipivot designs if they significant cost or performance problems. As much as folks on this forum are hobbyists, the folks making the tools of our hobby are hard-nosed businesspeople making engineered solutions to support it. If they couldn’t make money, they wouldn’t do it.

That was empirically confirmed for me during the auditions I mentioned above. Using the same source material choices (a Sheffield Harry James, a Mobile Fidelity Donald Fagen and a first edition Getz and Jobim), I couldn’t hear enough of a difference to call one a gimbal and another a unipivot. They were all using the same Ortofon LOMC (I can’t recall which now). It was a remarkable demonstration of engineering excellence. One does get what one pays for.

Especially for designs incorporating VTA on the fly. anyone claiming that there are VTF errors resulting from it or the bearing configuration don’t fully appreciate how the geometry is supposed to be employed. Geometry is geometry and the physics applying to it don’t change just because the bearing surfaces supporting the transcription engine have different designs. If the design is correct, that’s the end of the story.

I actually had a long conversation with Tri Ma before I purchased my Graham. I found him a brilliant man with a true gift for how to extract excellence through continuous evolution of a fundamentally well-engineered design. The only reason I didn’t go down that path was some advice from the inheritor of my table design (Kirk Bodinet) about the physical modifications my Sota Sapphire III required to accept the Tri-Planar. The Graham was a drop-in with more adjustability. I held my breath, dropped the notably higher coin and have been totally satisfied ever since.

Moral of the story: Audition, touch, adjust and buy the one you like. Forget about anything else and be happy.

Effischer,

Thanks for your detailed description of your experience.  I heard a same table/cartridge comparison of a Graham arm and an SME arm.  There were subtle differences in sound, but nothing so major that one would even think it had to do with some major fundamental difference in design.  There are many good arms out there of all sorts of design.  I’ve owned gimbal arms, an air bearing tangential arm, a Well Tempered monofilament (fishing line) arm and two unipivot arms (Graham and Basis Vector); I currently use the Vector arm.  The easiest to set up and adjust is the Graham.  
There are many designs that purport to do a better job of addressing this or that performance issue.  But, any design, even if it is successful at addressing certain concerns (e.g. tangential arms to reduce tracking error), will not be strong in some other aspect (at least theoretically) and even then such weak areas might hardly matter with a good arm.  

The arm that seems to attack almost all theoretical issues is the Reed T-5 and it is quite elaborate and expensive.  I’ve heard it, but not in a system I knew very well.  Fortunately for my finances, it would not fit on my table.