be careful not to wear a metal belt buckle when spinning vinyl.
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I am surely no "magnetic field" expert, but i would think that you would neet to shield the areas directly above ( where the tt is ), below ( where the rest of the gear may be ) and behind ( all of the low level cabling and power cords ). I would think that this could work wonders, especially if you could find a way to mass load the levitating TT. Not only would it be completely isolated from floor-borne vibrations, the mass loading would also minimize air-borne vibrations.
Just do it and let us know how it turns out : ) Sean
I built one for my TT after moving it to a location where floor vibrations could not be completely dampened. My major problem was keeping the magnets apart. They can easily be coaxed into flying together unexpectedly and any unfortunate appendages falling between them will suffer the consequences.
I have heard no difference between the table with and the table without the strong magnets nearby (except for the suppression of floor vibration which works admirably). The field is essentially static and strongest at the corners of the platform where the cartridge isn't, so I wouldn't expect there to be much of an effect on the signal. I am using a Grado moving iron cartridge rather than low output moving coil, so your mileage may vary.
Sony made opposed magnet feet in the 70's. "Espirit Line" methinks it was called. Heavy and expensive too. Eliminates all the home made contraption issues. Actually worked. Made that Bulgarian Scrubwomen Choir (the 'reference' show-off LP at the time) really open up and separated the voices. IMHO, fully disclaimered, and showing my age.
I'm no scientist, but wouldn't something "floating" on a magnetic suspension be more prone to move with airborne vibration? I thought the theory of vibration isolation was generally to solidly couple the platform to something that wouldn't move (i.e., the foundation). I guess you could make it really, really heavy, but you still have damping problems--if something is magnetically suspended and you displace it, won't it oscillate until friction with the air slows it down?
I guess, if you use electromagnets, you might be able to do something to change the repellent magnetic force dynamically and damp it... There's the idea--some form of active electromagnetic compensator. Then the only problem is finding a reference that is isolated and doesn't change.
Seriously, I'm no engineer, but the theory seems flawed...
I have also considered that idea, but did not follow through on it. The reason I didn't, is that I have since come to the conclusion that direct coupling to the floor is a benefit and not a detriment. Just as speakers sound better on spikes that directly couple them to the floor, I believe that turntables need this same type of coupling. I realize that this flies in the face of the generally accepted wisdom of decoupling and isolating. Sometimes, generally accepted wisdom is not correct. To elaborate, I think that to get maximum detail and dynamics out of your turntable, it needs to be floor coupled. The coupling itself is to provide needed rigidity for the transducer to operate correctly. Literally tons of PSI are present at the stylus/record interface due to small contact area. Although this pressure is spread out over the full area of the platter and through the spindle and into the base, it is still there. The arm, though coupled to the base at the pivot, has a static balance and effective mass load. It has moment of inertia which tends to keep it in its current state. If the platter/base assembly is allowed to move in any direction whatsoever, the stylus pressure in the groove will be influenced in a negative way. You may say that the arm will move with the movement of the base, but this is not so. Only the pivot end will move with the base and the headshell end will "float" relative to the record. This changes stylus contact and tracking force much like a record warp would, except usually much less. Since a magnetic, or fluid, or air, or spring base behave similarly, they are compressible in a vertical direction and will have negative results on dynamics at least.
Now, to address the vibration issue, which IS real, I believe that correctly engineered damping is the answer. If the vibrational modes of the turntable, base, and platform are properly addressed as a system, the rigid floor coupling can be maintained, and the vibration reduced sufficiently. This is the aim of some vibration control methods like sand tables and lead shot loading. Vibrations are dissipated in the small granules as heat, and the load path to the floor remains intact and coupled. My 2 cents.
From an engineering standpoint, these types of mag-lev designs are not truly isolated in 3-dimensions. More like 1 dimension for the designs I've seen. and, it's physically impossible to have them independently floating in 3 dimensions. It's provable from a science standpoint or just try it with 2 magnets and you will see this easily. The floating shelf platforms are really no different than just 4 springs. In fact springs may be more isolated than the maglev stuff. The designs I've seen have vertical rods to keep the shelf aligned. These function to connect the two shelves, nearly rigidly, or at least with as much force as keeps them separated magnetically. Sure they look neat but do they break any new ground, technically? The answer is no.
As Ed says, my platform does only isolate in the vertical dimension, as the others are blocked by bearings and posts. The fact that you can't levitate in more than one dimension was derived in the previous century. The platform does act like it is suspended by four springs, however actual springs could not operate in the same region nor change parameters as rapidly as the magnets do, so they are better than other mechanical systems. In my arrangement, the turntable rests on cones and a black diamond racing shelf which are on top of the platform. Together they are a significant mass and do not tend to move. My interest is in suppessing the large transient vibrations generated by, say, someone dancing on my wood floor. It does that very well. Due to the mass of the system the vibrations are not transmitted to the table and dissipate elsewhere.
I stayed up most of the night doing some experimentation. These are my results:
Note that my music room has a carpeted concrete floor.
Moving my preamp and turntable into the garage which is next to my music room provided no audible improvements.
Placing the turntable on an air bladder platform provided no audible improvements.
Some tack welding, several solenoids, a car battery and a 3/4" piece of MDF levitated (pretty crude setup but it worked) and a lot of effort in leveling this device provided no audible improvements.
Back to basics.
I appreciate all the input. I believe that John clarified what conditions the levitating platform would be useful in. TWL, I have a suspension turntable and can attest to your practice of coupling to a solid surface as having always worked well for me. I do think the solenoid system could offer some real benefits except if it got unplugged. :~(