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Platter Levelling Issue

I have just purchased a new "bullseye style" bubble level that has graduated markings on it to allow you to determine the degree of misaligned conditions - each marking is supposed to represent 5/1000's of a degree

I initially verified it's accuracy by levelling a flat surface and then rotated the level in the horizontal plane in place - the position of the bubble did not move as I rotated it through 360 degrees.

I then placed the level on the plinth by the base of the arm and levelled the turntable - I believe the mounting method of my arm should ensure the arm is now perpendicular.

I then place the level on my turntable platter and took a readings as I rotated the platter through 360 degrees

Turns out the platter is not quite parallel to the plinth
- I don't think the bearing is damaged, since the degree of misalignment was consistent and always in the same direction as I rotated the platter - so the platter is not quite aligned with the plinth

The margin of error I observed is 10/1000's of a degree according to the gradations on the level

So, until I can rectify this - my questions are...

1. should I ensure the platter is level at the expense of a perpendicular arm

2. should I ensure the arm is perpendicular at the expense of a horizontal platter alignment?

3. Am I being 10-1000's of a degree anal :-)

The arm is an Audiomods Series 3 that has Rega style bearings and from what I have read on the web it is more important for arms with a bearing system like the Rega to be perpendicular

I have read other posts on Agon of a similar nature, but there was no mention as to the degree of misalignment

Any input would be very much appreciated

Many Thanks
williewonka
mikelavigne
2,200 posts
 
agree that with pivoted tonearms 'absolutely perfectly level' is certainly desired at the top of the food chain for ultimate performance, but absolutely dead-on-perfect is not critical for good performance. and really; getting a platter level should be an easily doable thing unless there are other problems. having the drive system aligned properly for best speed is maybe the most critical issue and if the tilt affects that then it ought to be corrected.

personally I have an active isolation base which is self leveling which eliminates the issue for me (assuming my plinth and platter are correctly aligned which with its design it's not an issue as it's one solid construct).

if you have a linear tracking tone arm then it's a whole different ballgame. it's absolutely critical that the arm tube which the arm wand travels along is totally level or undue stress is put on the stylus and cantilever......both from a tracking perspective and a stress failure of the cartridge perspective. with the Rockport Sirius III it was important to check the level of this arm tube regularly and adjust the air suspension to get it level. you would check it by tapping the arm wand (in the up position) to unweight it and make sure it stayed in the same place. if it drifted one direction or the other then you adjusted the air suspension.

so the importance of level varies. I'm not saying it's ever not important, only not to stress too much on the issue when there are bigger aspects to work on.
williewonka OP
3,082 posts
 
Syntax - It's all about the journey :-)

Yogiboy - you are correct - But I'm over it now :-)

wlutke - FYI: I purchased two levels from Ebay

http://www.ebay.com/itm/Spirit-Bubble-Degree-Mark-Surface-Level-Round-For-PRO-Measuring-66-x-10mm-/191383388818?ssPageName=ADME:L:OU:CA:3160

Coming from china I figured their quality might be "suspect". Turns out one was actually spot on, but the other was a write-off - guess I got lucky this time

I took everyone's advice and levelled the platter and I actually understand why it's so important - especially with the better cartrdiges.

The arm I'll get to in due course, but for now I'll live with the 1/100" tilt :-)

Many Thanks
last_lemming
639 posts
 
I use a free bubble app on my I phone and it's dead nuts accurate. I've cross checked it with real bubble levels and they zero out after I set it with the iPhone.
stringreen's avatar
stringreen
6,484 posts
 
There are many leveling apps from the Apple app store. Level the platter, then use a Fozgometer to get the cartridge accurately in the groove. I would not shim the arm...you want a solid connection to the turntable arm board.
swampwalker's avatar
swampwalker
5,138 posts
 
Stringreen's approach (leveling platter and then making sure azimuth is correct) makes sense to me to the extent that I understand the geometry and forces involved. However I would be quite hesitant to use an iphone app. As Doug Deacon has pointed out, the accuracy of that app would depend on a properly square,plumb, and level iphone case, at least with respect to the circuit board inside. I would be willing to bet some real $$ that Apple does not have a spec for that in their requirements for their manufacturers, and if they do, I cannot imagine that the tolerances are anywhere near what people have been talking about here. This is just a theoretical concern, not in any way suggesting that Stringreen or anyone else's set-up is in any way "wrong" or not optimal. In fact, I am pretty sure it's better than mine!
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