I wrote it to thread 12 inch Graham Phantom
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I am dealing with similar issues after upgrading our 9" Phantom to 12" Phantom II supreme. We needed the 12" arm wand for the new TTWeights Momentus Duo Drive table we just got in for demo and sale, which has an outboard arm pod.
I am ordering a new Mint LP protractor for the 12" arm and this is the info I got back from Yip atMint LP. The numbers are in mm. and recommend the Mint LP unit highly. The one I had for the 9" version worked extremely well.
"For the 12-inch Phantom tonearm the spec is totally different:
295.6/308.8 Mounting Distance/Effective Length."
Hope that helps.
But that is the thing,that these specs,which Bob sent me,does not work with me.
When I adjust mounting distance to 295,6mm,I simply cant make overhang 13,2mm. 13,2mm overhang is for Baerwald scheme.
I am getting around 16mm and than screw,which is holding cartridge in headshell hits the inner edge of headshell and I cant move cartridge anymore.
It seems to me,that Leff is bigger than 308,8. I made some calculation for Baerwald scheme and what can work with me is this:
Mounting distance 300
Offset angle 17,37
With these numbers,I will be able to adjust cartridge in headshell correctlly.
I just got Graham 12" last month and there is no spec available. The manual is still for 9/10 inch arm only. It only said to look at addendum sheet for 12 inch spec but there is no addendum sheet anywhere in the box that I could find. So far I use only setup tool from Graham which seems to work ok but I am not really overwhelm by the result. I am thinking of trying mint protractor since it seems to really help both JWM 10.5 and Reed 3Q significantly.
If you use an arc protractor like the Mint LP you will get the correct offset angle. As long as the arc protractor is designed for correct P2S for the arm you're using and you follow the alignment for zenith you will have the ideal offset angle. Just ignore the offset angle on the Graham 12" armwand as it is not correct.
... far I use only setup tool from Graham which seems to work ok but I am not really overwhelm by the result
Of course it sounds awful because it is wrong, the alignment flip is calculated for the short Arm. But don't worry, that way it was in use at CES and all visitors/reviewers were floored :-)
Go for PtoS with 295,6mm and use a 12" Alignment System, Dennesen or similar, then you are spot on
Sean, thanks for the tip regarding Reed mint protractor and Graham. I did not realize that both has the same 295.6 PtS and 308.8 effective lenght. I checked briefly with Mint and was surprise as to the difference between Graham's own tool and Mint. I will try to set up carefully with Mint tonight and see. I also have Clearaudio protractor (as I understand, it is the same as Dennesen, I assume with IEC-standard R min 60.325mm, I still have not figure out this whole IEC standard r min thing and the manual is only in German). However, there seems to be no easy way to place the protractor accurately with the set PtS. It seems that Clearaudio and Mint are closer to each other than Graham's by quite a bit.
I can not figure out what the fuss is all about, all you contributors of this thread ... you are very experienced analog afficionados and then you don't dare to improvise in this most creative and entertaining theme !
In my case I've had allways to deal with customised protractors for my 2 favorite tonearms (Pluto 9A & SAEC WE-308SX) but this is fun and never became a problem for me as far as I have this :
I can choose whatever it pleases my LP collection.
Dear Suteetat, Clearaudio is not the same with the Denessen.
"This whole IEC standard r min thing" is the last inner groove that is recorded to your LP. So, depending on your LP collection you can choose an alignment which suits better your preferred inner groove and see the changes of the tracking distortion on the graphic above. The only problem (not every one has the patience) is that you have to design the 2 new null points on a paper which has to be accurately bored to your spindle according the Pivot to Spindle distance.
1). First you have to draw the line from Spindle to Pivot.
2). With the compass tip to the Spindle point, draw an arc that represents your inner null point and a second arc for your outer null point.
3). With your ruler draw some closely spaced points (preferably with a needle)
counting from the Pivot point up to the Effective Length and progressively getting closer to the Spindle until you reach the Overhang.
*[This is your Arc Protractor]
4). With your ruler join the 2 points : from the Spindle point, up to where the small arc (of the inner null point) meets the Effective Length. Likewise join the 2 other points : from the Spindle point where the bigger arc (of the outer null point) meets the Eff.Length.
5). Draw the lines that are vertical to these two.
**[These are your 2 points for Zenith Alignment]
6). Now you can cut the Spindle Hole
(after some strengthening of this small area by using 2 pieces -as a sandwich- of self adhesive tape that we use for protecting the wall when painting)
exactly centered to this full stop point that represents your Spindle point
(preferably using a 2 pointed compass to cut smoothly).
***[This is your custom jig]
Before you start to design your own original protractor, you must have some experimental time with the VE comparator, enough for you to comfortably decide the graphic plot that suits your LPs. So pick up your 20 most enjoyable LPs and with your ruler find the innermost groove from the spindle point.
I'm sorry if Ι was tedious & boring but anyway this is what I am doing for my two quite distinctive tonearms.
To further promote this alignment theme, I'm taking the risk of saying that the tonearm manufacturer does not have to deal with the specific geometry of the designed tonearm, but only with the mechanics! And that's because he doesn't have to know what is the innermost groove of your LP collection. Neither he can enforce you to use only his prefered alignment, just because he gives you a jig or a specific Eff.Length, ONCE HE IS USING A SLOTTED HEADSHELL!
Within the physical limits of the tonarm & the armboard under use we can decide entirely free by our listening.
I have the Dennesen, the Clearaudio, the Pluto and the Project of this family of protractors. Even if the Dennesen was still available, (discontinued) I would buy the Clearaudio instead. Ιt gives the better sound (especially the r min=75mm) it has 4 options, it is fairly accurate and is a joy to use. But although I'm allways starting from here, it seems impossible to resist in making my own customised paper.
I'm starting from the furthest permittable Pivot to Spindle distance (on each particular armboard) and then I'm checking if I can reach the Effective Length which corresponds to this according the protractor. From this place, the VE comparator takes order to modify the curve of the plot to my own priorities. Usually I don't change the Pivot, but experimenting with the Offset Angle instead, watching the tracking distortion, and the innermost & outermost grooves in the plot of the VE comparator.
BUT ... even if you don't bother to make your own changes, (especially if you don't care to change the null points and stuck with the Baerwald alignment) it is worth to find a 2 point protractor, in order to adjust precisely the zenith! because this kind of protractors, they strictly offer only the inner null point and THIS IS NOT ENOUGH by all means!
In every other case you have to design your own paper with outmost care. It's fun and it helps to understand the whole situation that is taking place there and most importantly it gives you the essential self-assurance that nothing left to chance.