The necessity of a plinth

Hi Lewm, the idea of dampening of spurious vibrations is a nice one, but you actually don't need high mass to accomplish this! What you need is a low impedance path for the redundant kinetic energy, which should have a constraint layer construction. Such a construction is not by definition high mass --> look at the theory behind the Symposium Ultra Platforms.

Chris

Interesting points Lew. Wish I remembered more of what I was supposed to have learned in Physics, i.e. energy travel.

From what I understand from a discussion with Albert, his brass rod contacts the bottom of the bearing housing under the motor. How much energy is then transferred downward to the iron block sink, thus not upward through the spindle, platter, and record I have no idea. But it is easy to accept that this will have some positive effect.

Part of my lack of understanding is the assignment of a diode effect on energy travel to some isolation devices by a number of hobbyists. For example I think the effectiveness of "tip toe" style devices relies more on the concentration of mass than on transmitting energy in one direction but not the other. Like the old story that a 120 pound woman in high heels exerts more pressure per square inch than an elephant.

So for now it seems we are left to trial and error in our own systems.

As much as we wish they were, cones do not act as diodes.

Cones have the shape of the electrical symbol for a diode but this doesn't mean they act as (mechanical) diodes. Btw, why should mechanical devices act like electric devices and vice versa? Personally I think the mechanical diode theory is not a scientific one.

Chris

This has absolutely nothing to do with the differences between DD tables and idler tables, but IMO a cone-shaped footer can be an asset IF one first determines the loci of standing waves on the shelf (which would be based on the resonant frequency and is best located with a stethoscope) and then places the tip of the cone on a vibrational node (i.e., a point where the shelf is not vibrating). This would then prevent the shelf from transmitting vibrations up into the equipment, because the equipment would only "see" the null points in the shelf. Like you guys, I don't quite see how a cone will prevent transmission of energy in the other direction. However, is not a diode a one-way device? Ergo, we have a mechanical diode. Maybe the term "diode" is not semantically appealing in this case.