MintLP arc protractor
Greetings, The problem here is that the turntable in question has already had its tonearm mounted, and save some potential play in the mounting hole, its pivot-spindle distance is fixed. Normally, you establish a pivot-spindle distance from the effective length before mounting the tonearm, but using (for example) the Ellison spreadsheet, you can work this backwards. So, assuming it's an accurate Rega Stevenson mount, you have a 222mm pivot to spindle distance which resolves to ~ 237mm eff. len. for Stevenson and ~239.3mm for Baerwaald. This 2.3mm (approx.) difference is what Doug was referring to when he said you might run into problems with a "short" cantilever - meaning a cartridge whose stylus is positioned considerably closer to the mounting bolts than the 9.0mm statistical norm. There's a potential for your not being able to slide the cartridge forward enough in the headshell slots to achieve the 239.3mm effective length. This is why Yip is being so persnickety. As Johnbrown wisely suggests, you can do a proof of concept by printing out a Hoffman protractor. This will set your mind at ease. Cheers, Thom @ Galibier |
If you're concerned about your headshell slots having enough 'play' to allow you to mount a specific cartridge, I'd suggest you first print out an arc protractor on conrad hoffman's site http://www.conradhoffman.com/chsw.htm, using your measured Spindle to Pivot, as a test before you order Mint's device. Also, maybe doing that will help convince Mint that the StP that you've given him will actually work. |
Yip is a great guy and makes an outstanding product, but he can be a bit, how should I put it... "over the top" with regards to insuring that your spindle to pivot distance and effective length is exact. It took well over a month of back and forth emails and even sending numerous photographs of my setup to convince him that my Jelco arm did, indeed, have an achievable effective length of around 235mm. The MintLP protractor is painstakingly precise and I understand Yips need to get these measurements as close as possible. However, a millimeter or two +/- on spindle to pivot distance can usually be accommodated for via the headshell slots. All that being said - trust me that it'll be worth it in the end. It's the most precise protractor I've ever used. |
Since a Rega is not designed for Baerwald, *some* cartridges may be too short (from the plane of the mounting holes to the stylus) to be aligned using that scheme. The headshell slots may not allow shorter cartridges to be slid far enough forward to achieve alignment. Not a common problem, but not completely unknown. |
Polk432, "The mint LP will be more accurate. It is worth the money." Perhaps true but not the question of my original post. Yip is insistent on the correct spindle to pivot distance and I want to be certain that I've measured 222mm correctly before placing the order. It doesn't take much error to be a mm off. Wendell |
Finding the horizontal pivot point on my OL Silver (modded RB-250) was trivially easy... 1. Mount the arm to the table (no cartridge needed, keep the stylus guard in place if it's already mounted). 2. Stick a piece of scotch tape across the top of the bearing center. 3. Using a fine, felt tip pen, make a tiny dot on the tape where you *think* the pivot point is. 4. While viewing your dot from directly above, swing the arm back and forth through its arc several times. 5. Move the tape as necessary until the dot remains stationary while the arm is moving. Voila! 6. Measure from center of TT spindle to center of dot, using a fine lined metric ruler. Keep the ruler level or your measurement will be artificially lengthened. Move the arm until the dot's at 222mm and tell Yip. You'll be well within 0.5mm. 7. Don't forget to remove the tape! Save it for future use if you're especially cost-averse. This takes 2 minutes and costs $2 (for the ruler). Well worth it IMO for getting a good arm position before dropping $110 on a protractor. Doug P.S. No, I will not make up the tape and dot for those unable to do it themselves, whether for free OR for a fee! |
Hello Wendell, Yes, there would be a more accurate way to measure, but it would no doubt incure some costs. And I'm unsure if this degree of high accuracy is needed? I'm no Rega Arm expert, but I would think, unless you are using a Rega Cartridge, and buttoning up all three holes on the Cartridge might there then be a problem? I would assume the very best way, would be a large Dial Caliper, such as the machinist used, when he fabricated a new plinth for me on my VPI HW-19. I'd hate asking him the price of that tool, I'm sure it was not cheap. Machined Locating Pins were fabricated for both Bearing, and Arm Base. Then with Calipers, the required didtance was measured out. It is important, that any measuring tool be perfectly level when taking a measurement. Any sloping of the measuring tool from point A-B (Pivot-Spindle) will give an erroneous reading, most likely longer in length than the actual S-P distance measurement. I would think a good accurate Steel Ruler would be better as a tool. I wonder though, wouldn't this be true, with a slotted Headshell, if one finds the actual S-P spec of 222mm slightly off, say by +- .5mm-1.0mm, couldn't one then properly compensate by sliding the cartridge on Headshell, thus getting perfect alignment with the 222mm MintLP Arc Protractor? If I'm wrong about this, somebody please chime in! :-) mark |
