Linn Bedrok LP12 Plinth Upgrade

@lewm 

Not at all. Feel free to comment as much as you want. But expect what you say to be challenged occasionally. 

@elliottbnewcombjr  I have seen the video you posted and others that are more complete. The bearing is precise without having to be a tight fit! Remember, the bearing point is what the whole shaft rotates from. The bearing point is diamond hardened. Please do a little more research.

@elliottbnewcombjr

l have to agree totally with your deductions……l think the subject of tolerances in the shaft is critical for turntable stability.

l had a Thorens TD124 and experienced your claims for the very tight fit while ‘seating’ the shaft onto the bearing thrust pad.
My later table and my much loved classic period table of all time, the Logic DM101 Electronic is even closer in machined tolerance than the Thorens. After an oil change of ‘Gold Oil’ Mobil Velocite No.6, (l believe the Linn recommended oil) the time it takes the shaft to settle is about 10 minutes to displace the trapped air. I try to speed the seating process up with intermittent manual revolutions of the platter.

Vertical and horizontal tolerances in the bearing and shaft are just as critical as that found in a well designed tonearm.

l can’t believe there are suggestions made on this thread that the shaft tolerance is not important….that statement has to be plain nonsence! Without such a tight seat the platter shaft would slightly oscillate like a demented flag pole in the wind.

mylogic

Until you personally experience waiting SEVERAL MINUTES for a very heavy platter to drop into it’s bearing well, you cannot imagine how impressive it is. You mentioned 10 minutes, I am remembering around 6 minutes, just walk away, come back after a while.

I just jumped about learning a bit about the DM101 (I never saw or heard one), it seems it’s bearing, similar fine tolerances to the Thorens TD124 is the key to it’s following, I saw many comments about the springs, center spring, tweaking springs ..... but in all cases it’s the bearing that allows it’s superior bass performance.

I always assumed Linn had similar tight manufacturing tolerances, I remain shocked by what I saw in that video, and still wonder what made the clunk each time it was dropped into the bearing well?

It seems, from comments, the DM101 bottom thrust bearing was less susceptible to vertical movement than the TD124, or those vertical vibrations were curtailed by the softer spring suspension, as opposed to the firmer density rubber mushrooms Thorens used (I had installed new OEM mushrooms),

I built a skirt surround base like the Bedrock, with a continuous ledge (rather than Bedrock’s 4 corner blocks) with a continuous layer of foam supporting a top board cutout for the TD124, reduced but still didn’t solve the problem.

An old discussion here, just over 20 years ago

https://forum.audiogon.com/discussions/anyone-using-a-logic-turntable

simple search results 'dm101'

davey, Thank you for complimenting my system.  I presume you refer to the Sound Lab-based system.  As you may know, I also have a pair of fully functional Beveridge 2SW speakers in my second system, augmented below 80Hz by a pair of TL woofers I built myself.  I feel like a parent to both systems, and I love them both equally but for different strengths. 15-20 years ago, I got interested in vintage DD turntables, in part because the best ones are rare to find and collectible, and in part because I wanted to get away from belt drive turntables.  Along the way since then I also picked up a Lenco idler and modified it extensively. I am quite happy enough with what I have. My first real TT was an AR XA, back in the 70s.  Since then I have owned a Thorens TD125, a Transcriptors Reference (not super good but extremely fun to watch), a SOTA Star Sapphire Series III, and finally just brefore the DD conversion, a Hyperspace, which only became excellent after the addition of an outboard motor controller. My experience with the latter TT showed me that my Sapphire was not very good in several aspects, smearing piano decay and conveying vocalsl. Maybe there was something wrong with it. In any case, I have sworn off belt drives and especially spring-suspended belt drives. On the other hand, one of the finest TTs I have ever heard was my neighbor's Dohmann Helix. Go figure. So, while I am staying away from springs, I am quite impressed with the Minus K platform built into the Dohmann. Also, I heard an LP12 serving a system at the RMAF many years ago, and it seemed to be quite good. I got involved on this thread only because I was curious about the materials used to create the Bedrock and why it had to cost so much. I re-plinthed or heavily modified the original plinth for all of my DD TTs, except the Kenwood L07D.  So plinth materials is a subject that interests me.