zero cost magnetic isolation

got blasted by marble sized hail stones !.....

yes the larger 20mm dia magnets ....

stability is still an issue as they want to try and flip even glued down ! though once you have some weight on the "foot" the magnets are forced to find a positon of equilibrium within the sleeve.

I'll try to get the other feet sorted today ....

 

My turntable uses a Linn LP12 main bearing and sub platter, although it is very different in many (if not all) other aspects. I recently modified it so that the bearing is now levitated on opposing magnets. The modification can easily be reversed only requiring a small adjustment in VTA. I have been very happy with the results and intend to further explore modifying the internal sprung suspension elements to make use of magnetic repulsion.





The pictures shown above are actualy of an earlier prototype and the current model is different in a number of key areas. The lower magnet array is now a single large ring magnet, half the number of magnets are used in the upper array and a shielding disc is also used. Unfortunately, I havent got round to taking pics of the final design (MK4) but have been using it quite happily with my Naim ARO and Troika foer a couple of months now.

 

i can vouch for Ynmoans deck, it's deathly bloody quiet and absolutely unshakable even on the crappy suspended wooden floor he has in the attic. no matter how much you jump it doesnt budge.

 

wow ...nicely done !

 

I've always wondered with these magnetic deck things how do you ensure the magnetic field doesn't impact the cartridge tracking weight? Surely a magnetic field sufficient to float a heavy Linn platter can't be so localised that it wouldn't impact tracking / bias on a nearby MC cart (which also contain strong magnets)?

Tony.

 

yes but thinking about it due to the root mean square law ....obviously if the magnets are close [a few mm] then I would expect an effect ....but every time you double the distance from a magnet you reduce its "power" by x4...

 

Its something I wondered and googled this

which all seems somewhat familiar. Tenth post down is the claim that when you pout the magnets in opposition the magnetic fields are cancelled and he claims you can put such a device on top of a telly with no interference.

Knowing nothing about magnets I have no idea of this is actually true.

Should be easy enough to test and that and the reduction of magetic field strength so dramatically over distance would explain why both Clearaudio and Pro-Ject have both used opposing magnet platters as well as YMOAN rather splendid looking DIY afair, with no apparent issue.

 

he has his shielded with a thin disc of stainless under the sub platter.

there are two ways to test, crank up the volume and swing your cartridge over, or buy a little flux indicator sheet, a bit of plastic that polarizes light in the presence of a filed

 

The TT looks really well executed.

As far as the magnetic field goes:

In addition it would also be possible to use a thin sheet of 'Mu metal' on top of the platter to further isolate the cart from any EMI effects.

Details Here:

http://www.l-07d.com/tweaks.htm

Zanash:

I'm working on the name with the mods, until then It'll just have to be recognition by Avatar.

 

Only the administrator (Mark Telkman) can change your name. PM him your preferred name.

 

Indeed, the magnets do produce a vertical field which can affect a MC cartridge. However, it is possible to reduce this field enormously through a bit of careful design. I use three approaches; 1st the magnets are positioned relatively distant from the upper surface of the platter, 2nd the number of magnets used is quite low, 3rd a disc of mild (not stainless) steel is used to shield the cartridge from the magnetic field (this disc is also relatively distant from the surface of the platter. The platter is entirely levitated and the tip of the bearing no longer makes contact with the thrust pad in the main bearing. I cannot detect any issues with using my Troika and tracking eight is unaffected. No doubt the Naim ARO has many critics but few would deny its low friction/stiction levels.

 

ah, but it did sound better with the friction clamp on tonights listening.
came home and spun Lou Reed again, you need to hear it on my set up, yours is all over the place in temrs of balance, way more detail and PRAT but it's disjointed.

 

Please elaborate.

If I have time I will try the frcition clamp again today on a wider range of records.

You have to admit though that my 'magic mat' transformed the Rega - one of the bigest turntable changes I have ever heard.

P.S. Those Kef's of yours (not just yours almost all Kef's) ate notoriously 'well balanced' but also notoriously 'flat' (in my flat little world).

 

humm...not my impression of sq225917's speakers

 

Ah well...each to their own If you have heard Simon's system you are welcome to hear mine (I live just round the corner from him). To be fair my Epos speakers and Naim amps have been criticised in the past for much the same qualities as sq225917 describes - they just aren't that important (compared to some other atributes) to me.

If you have heard Simon's system you have almost certainly listened to CD through it and that brings a whole lot of different issues into the equation - you have to bear in mind though that I am a complete analogue devotee.

 

YNMOAN:

Where did you get your magnets from? Especially the circular one which sits on the sub-platter.

Thanks

 

I think the magnet you are reffering to is this one :



from here http://www.supermagnetman.net/index.php?cPath=41&page=3 its the R1410. However it is on the chassis not on the sub-platter. The magnets are held in CNC machined acrylic disks, though both the material used and the specific implementation have changed on my final design.

sq225917, after our listening session tonight I would respond by saying that your system may (and I only say may) sound more integrated but then it also sounds way less dynamic both in terms of micro and macro senses and I suspect this is the reason you hear greater 'integration' - it does indeed sound better with the light weight clamp though . I'm yet to be convinced that the Kef's produce the range of dynamic inflection I expect (though they are tonaly well integrated); I am indeed very 'Flat earth' in my audio priorities. Looking forward to hearing your system with a better cartridge - not that wowed by your Rega.

 

Finally built the piston feet....will need to play with them for a couple of days ...but initially they seem to work !

 

I too intend to make some magnetic repulsion susupension elements to replace the four springs used in my turntables suspension. However, this may not be possible due to the relatively high weight they will have to carry.

 

I think each of my feet will carry 2.5 kg ....quite how that will pan out for three I'm not certain.