New acrylic platter for the SL-1200/1210

[Mike_New]

Hi Chris

Thanks Mike

The OEM transformer is indeed shielded by Mu metal , this along with Richard's explanation as to how the Technics magnet works and i can quote him .

The ring rotor used in the Technics was designed to focus all flux patterns to the inside circumferance of the ring. There is a very simple test you can do to see this in action. Take a metal screwdriver blade and present it to the outer surface of the rotor ring. Do the same from the top and lower edge. Now present the blade to the inner circumfernace of the rotor (be careful here as you do not want a sudden shock impact of the blade against the ring in case you "chip" the ring. Just use a wee bit of sense here and retain a firm grip on the blade). What result do you find?


Remember basic physics and flux patterns in ring magnets. Most times flux leakage is associated with "air gaps" and is put to good use in loudspeaker drive units. The idea of a ring magnet is just that - direct the flux pattern where you want it. Look at the flux patterns for a ring magnet and you will see the pattern concentrated on the horizontal axis and any vertical axis flux pattern will be introduced via an air gap on the open face.

If we are not careful this discussion is going to get awfully complicated and theoretical.

Indeed the main magnetic flux is concentrated inside the rotor ring. And yes Richard is correct when he observes that the major magnetic force as observed with the crude device of a screwdriver is on the inside of the torus, which is where the reaction of the driver coils operate to drive the magnet around it’s axis.

However he seems to miss the point! There is a flux field on the outer periphery of the rotor, for the simple reason that it is not possible to totally constrain all the magnetic flux in the ideal way, which we would wish, when magnetizing a virgin ferrite ring. This outer peripheral flux can be regarded as leakage if you wish.

Flux leakage has nothing to do with air gaps, and it certainly is not flux leakage that drives motors, quite the opposite!
In fact by definition 'Flux Leakage" is the stuff we do not want!!!


When Richard talks about his basic physics, he does not seem to have any understanding of the fact that the "air Gap" generates the electromotive force; the power is transmitted across the air gap! One of the fundamental facts of nature that is not even today, fully understood. Flux fields do not require an "Air Gap" per se' to exist, rather they can occur wherever there is an unshielded "air space'. By definition, one normally refers to the "Air Gap" as being the space in which the magnetic flux is constrained to produce the power.


When he talks of loud speaker drive units, these are nothing more than basic linear motors operating within an air gap.

When I refer to flux leakage, I am referring to any and all, magnetic fields that are present where we do not want them, and which can be detrimental to the performance of the “system” unless adequate attention is accorded to shielding. Think “HUM” and consider how difficult this can be to constrain, after all it is only the magnetic flux generated around a simple wire by the flow of electrons.

All I am saying is that there is a powerful magnet bolted to the underside of the platter, and however well designed it might be, there will most certainly be a magnetic field of some sort. It is surely prudent for us to consider this when we talk about platter materials.

[Marco]

If we are not careful this discussion is going to get awfully complicated and theoretical.

Indeed...

Whilst this is all very interesting, up to a point (as far as anyone here can understand the technical nature of what is being written), I don't think we should be having discussions based on information relayed from emails by non-members.

Whilst I value Richard's opinions, if he wishes to engage Mike in debate on the matter of platters, then he should go through the normal channels and register here as a member, whereby he can then contribute to the discussion properly.

Richard always seems to have plenty to say (much of which I agree with), so I've never understood why he restricts his comments to emails, and shuns the opportunity to express his views on the forum.

Marco.

[MCRU]

mike
go take a chill pill, its a turntable platter, hardly a life or death issue is it boss?

as regards time frame to hear the sonic difference of your goods, are you saying there is a burn in period for a platter and bearing?

so is it at it's optimum performance threshold after a set period of time?

if its so fantastic surely I would hear the improvement after 5 minutes?

BTW you don not know what bearing and PSU I have in the house and how do you know it's inferior to yours if you don't know which one it is?

[Marco]

Lol - so which bearing have you got, then daftee? I did ask you before, and now I'd like to know

Marco.

[MCRU]

The Technics has been dis-mantled and sold for spare parts, end of. I am now looking for a forum where I can have a rational discussion about Garrards without being insulted.

[Marco]

Lol - aye, very good!!

Marco.

[chris@panteg]

Indeed...

Whilst this is all very interesting, up to a point (as far as anyone here can understand the technical nature of what is being written), I don't think we should be having discussions based on information relayed from emails by non-members.

Whilst I value Richard's opinions, if he wishes to engage Mike in debate on the matter of platters, then he should go through the normal channels and register here as a member, whereby he can then contribute to the discussion properly.

Richard always seems to have plenty to say (much of which I agree with), so I've never understood why he restricts his comments to emails, and shuns the opportunity to express his views on the forum.

Marco.

Hi Marco

To clarify , Richard didn't ask his views to be posted on this forum ! I simply asked him how he believes the Technics magnet works , I also asked his permission to post this explanation , and if this breaks forum rules and ethos , then the fault is mine entirely ! I just thought it was important enough in this instance .

But also to add that as this new platter is all Arthur's work , then I'm rather persuaded that he must have looked at the possibility of any magnetic flux leakage and found it not to be a problem ? Perhaps Arthur could elaborate .

One other thing to add is that Richard's own choice of platter is an alloy one bonded with copper plate ! Either the OEM modified or a bespoke platter.

[Marco]

Hi Chris,

To clarify , Richard didn't ask his views to be posted on this forum !

No, I know, but they often end up here anyway, via you!

I simply asked him how he believes the Technics magnet works , I also asked his permission to post this explanation , and if this breaks forum rules and ethos , then the fault is mine entirely ! I just thought it was important enough in this instance .

No rules broken, dude, but I'd rather that any views being expressed on this subject (and discussed) were those belonging to members of AoS, otherwise it gets a little ridiculous.

But also to add that as this new platter is all Arthur's work , then I'm rather persuaded that he must have looked at the possibility of any magnetic flux leakage and found it not to be a problem ? Perhaps Arthur could elaborate .

I've asked him, so he will comment in due course. Right now he's loaded with the flu.

One other thing to add is that Richard's own choice of platter is an alloy one bonded with copper plate !

Marco.

[chris@panteg]

Hi Chris,



No, I know, but they often end up here anyway, via you!




Marco.

Yes , then slag me off not Richard !

[Marco]

Lol - I'm not "slagging off" anyone! Where did you get that idea from?

Marco.