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On 22/02/2020 at 21:40, runforfree said:

If you imagine the platter is a level pier then the armboard is a ship which can pretty much move anyway in relation to the pier.

I returned from a weekend away from the forum to find this. Even allowing for the respect due to fellow forum members, the statement is so fundamentally incorrect as to fact that it calls into question the validity of the rest of the post of which it is part. Lest people unfamiliar with the the LP12 are reading this topic, the record needs to be set straight.

The whole engineering concept of the LP12 - which long predates its development - is that the bearing (and therefore the rotating turntable) is rigidly connected by the sub-chassis to the armboard (and therefore the arm mounting). The whole assembly (platter, bearing, subchassis, armboard and arm) is then suspended on sprung mountings from the top plate of the deck. The purpose of this arrangement is twofold - to enable the stylus to track the record groove with an accuracy that  is probably measured in microns, and to insulate the primary components of the deck from external noise and resonances. Anyone who has seen an LP12 in operation will know that the armboard and platter move in complete unison; the "ship and pier" analogy is entirely false.

This arrangement of components is common to all LP12s, of whatever age or specification. It is directly relevant to the current topic, because, for the deck to function as intended, the rigidity of the sprung structure needs to be maintained and the sprung suspension needs to be properly set up. Further I need not comment, as the relevant points have already been made earlier in the thread.

David

Edited by DavidHB
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If I may, I would like to expand on David’s post above.

The world of turntables is full of choices and if poster runforfree elects not to use an LP12 then I would imagine nobody really cares one way or the other. That said, there is much in his post which is just opinion albeit presented as fact and also, I sense, a basic misunderstanding of how an LP12 works.

As Ivor T himself said - I have never met anyone who knows less about the LP12 than me....

Statements such as “there's not one single aspect of LP12 performance which beats these turntables” are easily dismantled. For example, one of the brands he recommends is certainly very well made mechanically but its electronic speed control simply does not work. No matter how precisely one tries to set correct speed it endlessly wanders either side of 33 and the effect is clearly audible. A 1975 LP 12 doesn’t.

All turntables are a compromise. Does an LP12 sound great in your living room? Of course. Does it sound as good on the back of a motorbike...nope. That’s because it is designed to work in your front room and not on a motorbike. That would require a completely different design, again, with its own compromises.

Ironically, the ship and pier analogy is accurate albeit nowhere near the level the poster presumes. Let’s go back in time...

Early LP12 arm boards were simply a slab of medite held to the sub chassis with three wee screws. A Linn tone arm collar was held by three bolts passed through three washers tightened against the arm board. The subchassis was kite shaped therefore narrowing under the arm board.

At a microscopic level:

the front and rear of the arm board flexes vertically

the screws are smaller than the holes in the sub chassis so the arm board rotates horizontally 

the screws are easy to over tighten and strip their thread

the arm collar bolts compress the medite and go slack

To recognise the limits of microscopic shake, rattle and roll be aware your stylus is attempting to track deflections in the groove of fractions of one billionth of one inch. The scope to lose information is simply enormous.

Linn have done much over the years to minimise the above. A current arm board is multi-layered with a Formica laminate on both surfaces. It flexes less, doesn’t easily compress so screws and bolts can be better tightened.

A Majik subchassis is both structurally stiffer and enlarged so it now supports the arm board front and rear. The arm collar bolts clamp to the subchassis and not the arm board for a tighter fixing.

A Kore replaces the arm board with a single piece aluminium slab bonded, not screwed, to the subchassis. The arm collar is fixed as above. It begins to approach a theoretical ideal of platter, subchassis, tonearm, cartridge being one single unit with only the record groove driving the stylus.

A Keel is the closest to ideal - single piece subchassis, armboard and arm collar. Beyond that you have to compromise with movement. To play a record the platter has to revolve and the tonearm has to move up and down and left and right. Tighter bearing tolerance and tonearm rigidity are therefore part of the solution.

The poster’s desire for azimuth correction is perfectly valid but can only be offset against introducing more moving parts...greater than billionths of an inch...and ergo less rigidity. You pays your money and you makes your choice.

To give further context a Majik subchassis to arm collar has 25 component parts.

A Kore has 15.

A Keel has one....

 

Edited by Monkey Wrench
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53 minutes ago, Monkey Wrench said:

Ironically, the ship and pier analogy is correct albeit nowhere near the level the poster presumes.

An interesting take on the point. If I understand your informative post correctly, you are saying that the analogy is correct insofar as the technology of any particular implementation is unable to provide the degree of rigidity required for the relationship between stylus and record groove to be maintained with the ideal (microscopic) degree of accuracy. That is of course true; nothing is perfect in an imperfect world. And the problem will be the same for any turntable design.

My concern was that runforfree was suggesting, at least to an uniformed reader, that on the LP12 the plane of arm movement was designed to move with respect to the plane of the platter, whereas the reverse is in fact the case. And the ship/pier analogy is rather too dramatic for your interpretation to be obvious. As a regular user of seagoing ferries, sometimes in bad weather, I am all too aware of just how 'independent' the movement of a vessel and even a floating linkspan can be ...

David

Edited by DavidHB

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Hi David

Indeed. The ‘perfect’ deck, arm, cartridge combo would be milled from a solid block of, say, an aluminium or an alloy, eliminating all unwanted movement between and within each component part...

...except the platter would not go round and the arm couldn’t move. This is the compromise built into any record player. What effectively separates one deck from another then is build quality - tighter tolerancing, better materials, and so forth with regards to it’s application - front room or back of motorbike.

Potential stylus movements generated by the groove are down to the wavelength of light ergo anything you can do upstream to minimise mechanical movement which both subtracts signal and adds noise is a good thing. 

The degree of rigidity you refer to is, using current materials and technology, as good as it gets with a Keel whereas earlier version subchassis/armboard combos do flex enough to lessen the deck’s performance potential. Kores bridge that gap.

The function of the subchassis is to lock the platter and arm together so if the platter/record lurches to the left then the tonearm assembly moves equally in the same direction. The stylus therefore sees no change in its position in the groove. The better the subchassis the less independent movement. The lurching is largely generated by music playing in the room - vibration basically - and is why Ivor designed the deck the way it is and to work in the room. He could have gone with plan B and designed a deck that stood outside the room and was therefore better shielded from airborne vibration but, no, he wanted the deck in the room with the loudspeakers.

It won’t please everyone but in that respect one could easily argue the most important part of the LP12 is the subchassis...

And this is why the record player is such fun and upgradeable - you cannot build a perfect record player but you can keep getting closer.

Let me know if more is required.

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TLDR:

If you're going to buy an old LP12 and you have had no hands-on experience with one, get it from someone who sells them/sets them up professionally or feel free to buy from a private seller but leave some pennies in the pot for replacing whatever may be broken. A service is expensive enough but if you have rough bearings on your MKIII Ittok you're going to have a bad time.

Either way, you're going to want to know a dealer or someone who can set them up like a professional as well as source parts.

Any age, any spec, any variation, it's a gamble when it doesn't come with a warranty!!

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42 minutes ago, Monkey Wrench said:

Let me know if more is required.

Nothing, I think, thank you. As regards the facts, we are of one mind.

As I said, my concern was as much about the impression the analogy might give, as about the fact that (as originally stated) it was factually wrong or at best very misleading. I am grateful for your help in setting the facts straight.

David

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55 minutes ago, bruisedponpons said:

Any age, any spec, any variation, it's a gamble when it doesn't come with a warranty!!

Often, it's a gamble even if there is a warranty; risk is unavoidable. The real question is always whether the gamble in question is worth taking, and that will depend on circumstances. The OP's circumstances are not the same as those of us who have a selection of accessible Linn dealers to choose from. From what I can see, he would be better off taking the superior and less risky but significantly more expensive option, but I don't have all the facts.

David

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16 hours ago, Monkey Wrench said:

 ...The ‘perfect’ deck, arm, cartridge combo would be milled from a solid block of, say, an aluminium or an alloy, eliminating all unwanted movement between and within each component part...

The requirement is essentially for everything to keep still whilst it's moving about !

That's the minor contradiction that turntable designers are always up against :D

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23 hours ago, Monkey Wrench said:

It won’t please everyone but in that respect one could easily argue the most important part of the LP12 is the subchassis...

Old Skool Linn Dogma has the bearing at #1 in the hierarchy, but the bearing needs to be rigidly supported somehow to be useful...hmmm.... 

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1 hour ago, Clavius said:

Old Skool Linn Dogma has the bearing at #1 in the hierarchy, but the bearing needs to be rigidly supported somehow to be useful...hmmm.... 

I would take a Cirkus/Kore over a pre-Cirkus/Keel (would that even fit?). That's the hierarchy.

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1 hour ago, Clavius said:

Old Skool Linn Dogma has the bearing at #1 in the hierarchy, but the bearing needs to be rigidly supported somehow to be useful...hmmm.... 

The "hierarchy" is a suggested running order for upgrades, no more and no less. What it says in the present context is that the first improvement one should make to the deck under discussion (that is, if it is worth improving at all) is the replacement of the bearing. As, by happenstance, that will involve most or all of the work needed for a full service, which is what that deck most definitely needs, that would kill two birds with one stone. But the deck may well not be worth the cost and effort, even at what we would regard as a much more realistic purchase price than the $1,500 that is currently asked. The new owner could soon be in a situation where all that is left of the original deck after necessary upgrades and replacements have been carried out is a lidless plinth that has seen better days.

David

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2 hours ago, DavidHB said:

The "hierarchy" is a suggested running order for upgrades, no more and no less

I have no wish to get into a handbags at dawn keyboard fight with the most eloquent member of this forum but, I would give the concept of “hierarchiy” a bit more importance than that. I would rather say it is a Linn ethos and core principle permeating the company like the principle of “tune dem”. It was also a pretty revolutionary, or as people would say today ‘disruptive’, concept in its day.

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3 hours ago, Clavius said:

I have no wish to get into a handbags at dawn keyboard fight with the most eloquent member of this forum but, I would give the concept of “hierarchiy” a bit more importance than that. I would rather say it is a Linn ethos and core principle permeating the company like the principle of “tune dem”. It was also a pretty revolutionary, or as people would say today ‘disruptive’, concept in its day.

Actually, in our own ways, I think we're probably both right. You are certainly correct in saying that Linn used the thinking underlying the hierarchy both philosophically and disruptively. I would hold on to the point that the principal value of the concept for ordinary users is as I described it. And the discussions we have had in this thread and elsewhere on the forum should have made it clear that the value is by no means trivial.

And thanks for the compliment. It's nice to be called "eloquent". Sadly, "wordy" is often nearer the mark ...

David

Edited by DavidHB

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True in many a context,

... but with regard to hierarchy,  its  still sometimes difficult to convince folks that the bits you can't see are the most important bits :D.

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