Perimeter Ring Clamps: Yay?, Nay?, Sources??

It is sooo good to benefit from your collective experiences. I always do,

thanks to everyone who responded,

Elliott

mulveling, I am surprised to learn that the Benz cartridges you named would have such strong magnets, because they also have high-ish internal resistance for an LOMC, which suggests that the coils have many windings, yet the output is "low". Thus you’d think the cartridges could get by with a weaker magnetic field. On the other hand, my Ortofon MC2000, with an internal R of only 2 ohms and a vanishingly low output is probably dangerous for anyone with a pacemaker; its magnets are scary. The MC2000 inadvertently revealed to me that the Kenwood L07D platter sheet (made of stainless steel) is mildly ferrous; the MC2000 nearly committed suicide by squashing against the sheet. Since then, I had a copper platter sheet made for the L07D; better shielding of the cartridge from the motor EMI and totally nonmagnetic.

@lewm those Benz models use a Ruby plate to wrap the coils around. Most cartridges use a ferrous material which increases the output level for any given amount of coil windings, but also (supposedly) causes the assembly to disrupt the magnetic flux when in motion. The downside of the Benz Ruby approach is that it requires much more coil windings to create the same output level (compare to their highest iron cross model Ebony L with 0.26 mV output from 5 ohm coils, or Zebrawood L at 0.4 mV from 12 ohms). But it can also use a much stronger magnet because the armature is not reactive to it. Look at the Gullwing (Ruby) magnet in pics, it’s twice the size of the Glider (iron cross) with the same open body design.

There is an interesting video with Mr Fremer and the Windfeld Ti designer where he briefly mentions the choice of armature material that balances between the two - only slightly ferrous. The Anna uses a completely non-ferrous armature, but not Ruby (polymer?).

Some time ago I too learned you have to be mindful of MC cartridges on some metal platter :)

What I need, is for someone who has a Perimeter Ring Clamp to come visit, mess/listen, decide!

Plainfield, nj

07062

Elliott, I was looking at my TT101 with your quest in mind. As you know, the two platters present the same problem for fitting a perimeter ring. There is very little margin for error. In fact I can think of no “off the shelf” ring that would fit. Certainly my Kenwood ring is not even close. So, if you do invite someone to bring his ring to fit your TT81, I’d advise you to be sure in advance that his ring has a hope of fitting.