A Copernican View of the Turntable System

I need to throw my 2 cents in here, as I have very high regards for Bob Graham's design.
And saying that I must add, that I am absolutely no fan of the uni-pivot principle in pivot tonearm design for certain reasons (which I won't discuss ...;-) ... for obvious reasons ...).
The new Phantom Supreme is VERY good.
As were it's predecessors.
The design of the Graham tonearms does ask for very good mechanical coupling and speedy energy transfer in the armboard and plinth however.
This has to be taken into account when mating the Graham tonearms.
That's why In_shore mentioned the possibility of mis-match with certain turntables.

... but is not the most practical and finest tonearm you can buy today.... as the advertisement on the Graham web-site explains. Deartonearm it depends what kind of choice you have (also in today's market). Nevertheless The Graham was and is a a consistently developed and in many steps refined design with a good build quality as well. But the basic principle parameters did not change very much. Very good means in my understanding Top of the cream for all turntable conditions. I am pretty sure that the new Davinci arm and yours maybe too will speak a word in the Top-Class.

I admire Bob Graham for having established an iconic brand and product. Also his service is excellent. I sometimes compare it with the Porsche 911, built since many decades with some changes.

There might be a new Phantom Super Supreme III in a few years and the community will love it too. Why not?

best @ fun only

hi.,lkoi

It's been a while since this thread was active and whilst browsing through my Home Page I noticed that there had been 266,812 views here!!?
Wow....that's a fair bit of interest?

I've been doing some thought recently on the arguments some (particularly Lewm and Dover) have put forward against the separation of platter/plinth and armboards....and the perceived benefits of having all these items inextricably 'linked' by a rigid structure?
The argument (as I understand it) is that there is a known geometrical relationship between the spindle and the arm-pivot...and the 'plinth' reliably maintains this correct geometry?

I propose that there is no guarantee that a plinth in fact performs this feat......and even if it does......it rarely maintains the correct 'levels' of the platter and the tonearm/s bases?

I have checked (with multiple bubble levels) the absolute level of the platter and the plinth and the tonearm bases of my Raven AC-2 as well as my Rega 3 and I was quite surprised.
When I levelled the platter.....the plinth was not level and the degree it was 'out-of-level' varied over the surface of the plinth.
On the Raven.......only one of the three armboards loaded with their individual arms.....was in fact level?!
This actually makes sense if you understand the tolerances involved in making and mounting the plinths and spindle thrust bearings.
If there is only 1° tilt in the support of the thrust bearing.......and there is likely to be more....this translates directly to a 'tilt' in the platter relative to plinth.
And depending on the construction, thickness, span and quality control of the plinth fabrication.......there could be deflection, bumps or troughs?
And if you have cantilevered armboards like the big Micros and Ravens......the deflection at the end of these can be significant depending on the method of fixation to the plinth, the length of cantilever and the material and thickness of the board.
A simple challenge for all of you:-
Check the individual levels of plinth, platter and tonearm support?

With individual armpods....their levels are adjusted precisely and thus the tonearms are mounted vertically.
The unattached platter can be levelled without worrying about plinth irregularities and the geometric spindle-to-pivot distances can be accurately set using something like the Feickert metal device.
Another test worth doing for everyone with a plinth.....is to actually check the spindle to pivot dimension using the Feickert device.
My experience shows that if you get an accuracy of 1-2mm......you're doing well.
With the isolated armpods.....I can achieve accuracy of 0.1-0.2mm.

This degree of accuracy may not be an important factor as adjusting the tonearm geometry to account for this error may mitigate against adversity?

I do however maintain, that absolute level of platter and tonearms is pretty important......although those happy advocates of the big Micro turntables may prove me wrong? :-)

Hi Henry,
I've mentioned the issue of incongruity between platter and armboard a number of times, but it seemed to fall on deaf ears. Your experience matches mine when I had the shop. Since most folk level their platter and assume everyone else is level, I suspect a significant portion of tonearms do not have their vertical bearings in line with the platter - probably losing about 40% fidelity in real terms. Imagine owning a Linn with a wooden armboard moving around as the temperature varies.
This is one big advantage of unipivots with self centering bearings..
The other incongruity I see a lot is the motor pulley out of level relative to the platter. When running a rubber belt I've heard big improvements from ensuring the motor pulley is dead level and aligned to the platter.