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Two Protractors - Only One Aligns

So I've got a Technics SP10ii with an SME 312S tonearm and an Airtight PC-1 cartridge.  I had MINTLP make a custom protractor for the 312S, and it aligns just fine.  Recently I acquired a second tonearm (Musical Life Conductor SE 10" Cocobolo) - a very uncommon tonearm with essentially no documentation available.  Since the MINTLP states that it is fitted to only my SME312S tonearm, I defaulted to using a generic turntablebasics.com cartridge alignment tool. I was told that the pivot-to-spindle (PTS) length for the Conductor SE should be 235mm, but again, there is no written documentation. With the TTB tool, I could not get alignment at any PTS length, and I varied it from 225 to 270mm. Frustrated and confused, I pulled out the MINTLP protractor, and was able to align the cartridge at a PTS length of 250mm (FYI, the effective length is roughly 265mm, though hard to measure with the tonearm in place).  Then, in the spirit of scientific inquiry, I checked the alignment of the 312S using my TTB protractor and NO DICE - it was telling me that the cartridge was out of alignment (contradicting the MINTLP).  What the heck is going on here?????

I know there are more than one different alignments people use (Loëfgren, Baerwald, Stevenson, UNI-DIN, etc.) - but between the two null points on the TTB protractor the stylus was off by around 10mm.  That is way too much to be explained by variable alignment methods, right? And since I had success with the MINTLP protractor, I would like to call it good, except for the warning on the MINTLP ("BEST Tractor is tailor-made for a particular tuntable tonearm setup. Using it on any other setup will result in error and do harm to your cartridge").  I don't get that either.  Aren't the null points the null points, regardless of which tonearm you are using on a particular turntable?

Those with a high degree of vinyl experience - please chime in if you can.  Thanks, Peter
peter_s

Showing 7 responses by lewm

lewm
6,770 posts
 
Peter,  believe the Mint and toss out the TTB.  I think your conundrum goes with it.  The TTB is not very accurate (because citing the pivot point by eye is not possible with +/-0.5mm error), even when you do plug in the correct data, which is another question as regards your current issue.
lewm
6,770 posts
 
Bottom line, now that I've re-read your OP and gone to the website.  First of all, don't expect the Mint you own to work with this tonearm unless the specs are identical to those of an SME 312S.  Seems your new tonearm is 10-inch effective length and the 312S is 12.  Not good. By fiddling with offset angle, you might get it to "work".
lewm
6,770 posts
 
I agree with wlutke.  Nearly all other tonearms have a fixed angle headshell offset, unlike yours.  The P2S (pivot to spindle) distance, effective length, and the headshell offset angle are intimately related and chosen for whatever geometry the designer of the tonearm had in mind (usually Baerwald, Lofgren, or rarely Stevenson).  This is why the MINT protractors are unique for each tonearm.  If by chance two different tonearms work with the same P2S and headshell offset and effective length, then a protractor made for one will work with the other.  By adjusting the headshell offset angle on your particular tonearm, you may be able to cheat a little on this rule of thumb, but I think the tracking angle error in between the two null points might suffer. (I would have to sit down with a pencil and paper to figure that out, and I don't want to.)

While I've never seen a Mint protractor, I believe it is an arc type, which is to say the stylus must ride on an arc drawn on its surface.  If you can get your stylus to do that, with the Mint placed over your spindle of course, that might be valid.  The TTB assumes a priori that you have mounted your tonearm with exact correct P2S and that you can then align the spindle-mounted TTB with the pivot by eye, which I think is fraught with error, and I do own a TTB which I never use. Slight errors in aiming the TTB at the pivot can result in large errors of alignment.  I also noted that the TTB is a few mm thick, and the mirrored side is on the bottom, whereas the marker lines are on the upper surface of the glass.  That also is a potential source of error due to parallax.

I'll have to go back and click on the URL to see how your tonearm is constructed.  Sounds like it might be a copy of a Dynavector DV series.
lewm
6,770 posts
 
Peter, Based on the info you provided, you own a $5800 tonearm.  Such an expensive tonearm certainly does merit the cost of a Smartractor (if you want universal applicability) or a dedicated Mint LP.  (Plus also you apparently own an SME 312S; nothing to sneeze at.) Because of its issues (difficulty of aiming to the pivot and parallax created by the distance between the mirrored surface and the grid lines), I would say the TTB is not up to the level of your tonearm. (Also, any play between the spindle and the spindle hole on the TTB is yet another potential source of error.) If you don't want to spend on a Smartractor or limit yourself with the Mint, I would also recommend the Feickert Protractor.  Either Smartractor or Feickert will work now and forever for any tonearms you may ever buy.  I own both a UNItractor, big expensive brother to the Smartie, and a Feickert.  My TTB stays in the drawer.
lewm
6,770 posts
 
Because of the adjustable headshell offset angle on your tonearm, I think you will still want some detailed information from the company that makes it. Like what exactly is the intended pivot to stylus distance, and what exactly is the intended pivot to spindle distance?
lewm
6,770 posts
 
If it's German, you might be able to get help from Dertonearm, who is the proprietor of Acoustic Sounds (I think that's the name of his company).  Probably you could send an email to AS and explain your dilemma.
lewm
6,770 posts
 
Thanks, folkfreak.
i couldn’t conjure up Dertonearm’s actual name. Going to the former distributor is an even better idea.
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