Nude Turntable Project

Halcro, I would not expect copper per se to do much to absorb or block a magnetic field, except by virtue of its thickness which would just physically space the LP and the cartridge that much further away from the source. I am glad to hear your report on the comparison between the TT101 and the Raven. There are many in the audio community who say otherwise, and I never could figure out a scientific basis for their claim, that you need a very massy platter to have good bass reproduction. It seems to me that a combination of torque and well done speed control would be as good. If you will recall, Dertonearm once wrote here that at minimum, a platter MUST weigh 35 lbs for good bass.

Lharasim. Are you certain that copper is not an effective EMI shield? TI Shield, which is a documented effective EMI shield, is composed of three layers: copper/permalloy/copper. True, it does not work unless the copper surface is grounded. Perhaps it is the permalloy layer that does the work. I don't actually know.

I just went to the URL provided by Aigenga. The photos show exactly what I did, as well, to create an EMI shield for my L07D. However, I never heard any "wum-wum" when the brake activated, either before or after shielding was installed. That site is the one hosted by Howard Stearn, who is an orthopedist by day and an L07D Lover by night.

Halcro,
there might be only one conclusion, get rid of the Raven :-)
isn't it time for a change? I don't know about the value of these modern machines right now. I always went for technology, musicality and a rare design when going for tables. My tables kept the value, they instead increased. I really don't get it why some audio friends pay horrendous amounts for everyday tables which basically copy an originial, to the better?

Lawrence,
It was magnetism......not RFI/EMI that surprised me on the Cu-180 turntable mat?
The Micro Cu-180 is indeed non-magnetic.
My ignorance levels on electro-magnetism run deep.......but I'm guessing that there are materials which can act as 'conductors' whilst others are 'insulators'?
That's why the stainless steel of the 'cradle' I designed became 'magnetised' by the strong magnetic field and why the non-magnetic aluminium platter of the Victor becomes 'magnetised'.....or at least allows the magnetic field to pass through?
The same effect must be in operation with the Micro copper platter even though it is 3mm thick?
I can understand the rubber platter mat being an 'insulator'.......but a 1mm piece of pigskin being a sufficient insulator bowls me over.....
And why a 2mm thick piece of vinyl is NOT an insulator.....I don't know?
I'm sure someone will educate me?
Where's Al when you really need him?? :-)

You're right Thuchan,
There appears to be 10 times more Cu-180 platter mats available for sale.....even NOS ones.....than Micro ever made in their day?

Similar story with the Orsonic headshells....:-)
Aren't the Chinese great?