Nude Turntable Project

Halcro, To reiterate, copper does not shield against magnetism, electro- or other, largely because, as you noted yourself, copper is non-magnetic. Also, electrical insulators that you list are not good insulators against magnetism. Stainless steel can be magnetized because it has a (low) iron content. Alu will be as good as rubber, i.e., not good. Distance from the source and ferrous materials are two ways to reduce the magnetic field.

Chris, I think you answered your own question re the Dynavector, if I understand you correctly. It seems there was no detectable contribution from the magnet at the rear of the DV pivot when your detector was at the headshell. Thus, I would think, there is nothing to worry about (based on the fact that you read the same value of 40-ish when the tonearm is not in the picture). Moreover, the DV magnet is actually two magnets held in place in apposition over the stabilizer blade that is fixed to the moving part of the tonearm. Most of the magnetic lines of force would stay localized to that area because of the interaction between the two apposed stationary magnets and the moving blade that is already deliberately created. Yes, I think DV knew what they were doing, as they have stuck with this basic design for nearly 30 years.

Same goes for the Verdier: it uses two huge magnets of opposite polarity to elevate the platter. The magnetic lines of force are therefore concentrated in that space between the two giant magnets. Stick your detector down there, and see what that does. Also, the thick platter gives distance from any possible problem up on the platter surface.

To be fair to Dertonarm Lew.....he was referring to belt-drive turntables with his 35 lbs platter comment.
His logic.....and that of many other belt-drive designers.....is that greater mass creates sufficient inertia in the revolving platter to overcome stylus drag?
He also advocates non-elastic string or thread drive instead of rubber which means that the platter is not insulated from the cogging of the drive motor.
This of course requires a superb motor design.
For a direct drive turntable with a quartz-locked servo motor.....particularly a positive and negative servo control like the TT-101......the lightest possible platter will make speed changes less perceptible than a heavy one.
A common mistake that critics seem to make when discussing quartz-locked servo control....is that the servo is always 'hunting' for the correct speed?
They disregard the notion that the speed is quartz-LOCKED. The speed is generally spot on and not 'hunting' at all. The only time speed correction may be applied is under localised untoward stylus drag when....as you correctly remark.....good torque and bi-lateral speed control come into their own.

Which leads me to ask myself. Dynavector is a well respected company. if they thought there was a problem with magnetism would they have built their tonearm to be joined with their cartridges ?

Good question Chris.
One would think not?

Thuchan,
Don't get me wrong.......
The Raven AC-2 is an excellent turntable providing very stable speed control and superb analogue performance when set up correctly.
It has audibly kept level with the TT-101 until this last 'nudie' change I have made.
And in my 35 years experience listening to all the best turntables I could access.....the TT-101 is simply the best.
The fact that I have extracted a performance level from the Raven that is so close......speaks volumes I think?
I will not be selling the Raven :-)