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LP12 Set-up - a brief overview.
2011-02-07, 16:58
Post: #11
RE: Setting up your LP12 - a brief overview.
Good stuff, Peter. much appreciated and comforting so far....

Thanks
CJ

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2011-02-08, 02:12
Post: #12
RE: Setting up your LP12 - a brief overview.
Thanks for doing this Peter... We look forward to more of this topic when its available.

SLM.
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2011-02-09, 13:48
Post: #13
RE: Setting up your LP12 - a brief overview.
I have no intention of ever 'dabbling' in altering, checking and/or setting my LP12 up myself but even i am finding this very interesting to read from a technical insight point of view - keep up the great work Peter
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2011-02-09, 20:24
Post: #14
RE: Setting up your LP12 - a brief overview.
(2011-02-06 22:28)sktn77a Wrote:  
(2011-02-06 18:28)Cymbiosis Wrote:  I've reported myself to HQ on the tread and if its considered ok to proceed with the overview, then I will.

Ah, over the years, I've learned that it's better to ask for forgiveness than permission...........

And that silence is agreement! Wink

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2011-02-09, 21:32
Post: #15
RE: Setting up your LP12 - a brief overview.
(2011-02-06 23:28)Cymbiosis Wrote:  So, the plinth is level and we are now ready to check that the spring bolts are hanging vertically. Sometimes this is referred to as bending the bolts straight. However, in reality, the bolts are seldom bent. What one needs to ensure is that the bolt is hanging vertically. The top-plate is relatively malleable and it is this area of the top-plate where the head of the bolt is secured by an M5 Nylock that bends/distorts and sometimes needs correcting (bending).

Why do we need to do this? Well, as otherwise there is little chance of having a quiet and pistonic bounce. There are various ways of correcting this as you might read in on-line guides, but the tool of choice has to be the specially designed T-Bar.

All Linn Turntable Specialist Retailers will use it and it allows for accurate correction of the bolt (top-plate area immediately around the bolt head) so the bolt can hang vertically.

[Image: p11004981.jpg]


How or what could cause the bolts not to hang vertically?

1) A loose nut securing the bolt to the top-plate.
2) Consequence of the works necessary in ensuring the top-plate fits rattle free into the plinth in the motor corner.
3) Poor handling, such as carrying the deck round with the platter still on and consequently all of its mass acting on the suspension, hence giving the bolts and particularly top-plate a hard time.
4) If the LP12 is packed well during transportation, only a major trauma would cause a problem here, if the deck has been set-up correctly. They should not move during car journeys for example.

KR

Peter

I think this is a great idea as I know there are people who just can't get to a quality LP12 technician. I also think that even those with no desire to get inside their LP12s may find the work that goes into optimizing one interesting. As other LP12 technicians were invited to comment and add as appropriate I thought I'd put in a few words here.

While it must be admitted that "straightening" the bolts is a bit tricky I thought we should at least give an overview of it here in the spirit of the thread. As you can see in the photo the Linn T-bar has a metal tube that slips up over the bolt from beneath and a horizontal bar with a level in it. Once you have made sure the plinth is level in the jig, both front to back and side to side, you can address the suspension bolts. After removing the spring and grommet (if the subchassis is still in place) you slide the T-bar up over the bolt and check the level both front to back and side to side (the view in the photo). If the bolt deviates from level you use the T-bar to bend it a bit to make it level (as mentioned you are actually slightly bending the top plate). You do this to all three so that the springs are able to truly bounce straight up and down. (Of course the springs will likely need some adjusting too for a true pistonic bounce but that will be covered later.)

The reason this is a bit tricky is twofold:

1) The T-bar is a bit of a loose fit on the bolt (I've heard the new one is improved but I can't yet confirm that). This means you have to check the level by pushing the T-bar lightly to one side and then the other and averaging the two to determine the actual level.

2) If the bolt is significantly off level you will sometimes find that it can spring back a little bit after adjustment. Whenever I make a significant adjustment to any of the bolts I prefer to let it set a while (usually a day but an hour or two is probably sufficient if you don't have the time to leave it set longer). Then I check it again and make small re-adjustments if necessary.

The other thing I wanted to mention is a slight difference of opinion on the importance of the additional stub on the newer top plates. While I agree with what Peter has said about the purpose of the stub and the ability to get close to optimum without it, I feel that there is extra performance available on a top spec LP12 from having the top plate with stud. The reason I say this is that I have found that the exact torque applied to the nut tightening this down does make a musical difference. Linn do quote a torque range but I have found that, like other fasteners, it has a specific torque which is most tuneful which, in this case, is near the bottom of the specified range. Since very small differences in torque do make important musical differences, I don't feel that you can achieve this level of performance without the studded top plate.

The only other comment I have is that I wish I could get one of those cool looking levels in the US. After seeing the brand mentioned in another post I tried to find them but it appears they aren't available in the US. I couldn't even find a mail order site in the UK for them. While my current level is accurate and works fine, it is larger and nowhere near as cool looking as that nice machined aluminum piece. (And we all know machined from solid aluminum sounds better.Smile)

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2011-02-09, 22:15
Post: #16
RE: Setting up your LP12 - a brief overview.
One thing to add is that after you have struggled with the top plate to get it perfect at all three sides you can ruin it all when you start using the T-bar to straighten the hangers. I have done this fault myself and had to start all over again with the dressing of the top plate.
What Peter showed me was to press hard on top of the steel plate at the same time you bend the bolt underneath. Then you prevent the steel plate to bend in a way you really don't want and only locally around the point where the bolt/hanger is.

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2011-02-10, 00:12
Post: #17
RE: Setting up your LP12 - a brief overview.
(2011-02-09 22:15)HBerg Wrote:  One thing to add is that after you have struggled with the top plate to get it perfect at all three sides you can ruin it all when you start using the T-bar to straighten the hangers. I have done this fault myself and had to start all over again with the dressing of the top plate.
What Peter showed me was to press hard on top of the steel plate at the same time you bend the bolt underneath. Then you prevent the steel plate to bend in a way you really don't want and only locally around the point where the bolt/hanger is.

Thanks for mentioning this. Yes, this is particularly necessary if you have any bolts that are significantly far from straight.

LP12SE Movingui • KRadikal • Kandid • Urika • Kremlin • LS-NAS • KRDS • Lejonklou Sagatun Monos & Tundra Mono 2As • JBL 3677s & 4645C Sub • NOKTable • Harmoni Mimer/Tor Racks
AV: Pioneer BDP51 BluRay • Akurate Kontrol • 2 LK280 SPARK • 4 Isobarik DMS • 2 DQ1W

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2011-02-10, 10:31 (This post was last modified: 2011-02-10 10:37 by Cymbiosis.)
Post: #18
RE: Setting up your LP12 - a brief overview.
(2011-02-09 21:32)ThomasOK Wrote:  [1) The T-bar is a bit of a loose fit on the bolt (I've heard the new one is improved but I can't yet confirm that). This means you have to check the level by pushing the T-bar lightly to one side and then the other and averaging the two to determine the actual level.

Yes Thomas, the new one is slightly improved, as the fit is now a little more snug on the thread. Smile And, as HBerg points out, supporting the top-plate from above with a hand will help, as in correcting the way the bolt hangs, particularly if the adjustment needs to be larger, it is possible to deform a larger area around the bolt head. This in turn could affect the quality of fit into the plinth. So particular care should be taken with the left bolt (as viewed from the front and nearest the motor) as if the fit of the top-plate is compromised, one would have to remove the top-plate again and re-fit, removing any corner rattles!Rolleyes

Anyway FYI. Just awaiting the green light from HQ to continue and thanks to all for all your input and positive comments.

KR

Peter

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2011-02-10, 12:23
Post: #19
RE: Setting up your LP12 - a brief overview.
(2011-02-10 10:31)Cymbiosis Wrote:  
(2011-02-09 21:32)ThomasOK Wrote:  [1) The T-bar is a bit of a loose fit on the bolt (I've heard the new one is improved but I can't yet confirm that). This means you have to check the level by pushing the T-bar lightly to one side and then the other and averaging the two to determine the actual level.

Yes Thomas, the new one is slightly improved, as the fit is now a little more snug on the thread.

Does this mean that Linn have resumed production of these?

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2011-02-10, 13:08 (This post was last modified: 2011-02-10 13:09 by John G.)
Post: #20
RE: Setting up your LP12 - a brief overview.
While we're discussing T-bar, how many new decks coming out of Glasgow need adjustment of the suspension bolts/top plate?

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