Instructions for a Turntable Basics Protractor


A friend has given me a Turntable Basics Alignment tool without instructions. Can anyone give me instructions for properly uusing this tool?
tayofiji

Showing 4 responses by dougdeacon

In addition to Markd51's good instructions, the trick to using the TTB well is to get your eye used to the parallax (dual images) from the mirror. Some people find this distracting, but in fact it is the best feature of the TTB and the one that makes it more accurate than non-reflecting protractors.

Once you get the hang of looking at both the direct and reflected images of the grid, and squaring them up, you can be certain you're looking exactly down the centerline of the grid. That kind of accuracy isn't possible with a single image protractor.

This takes some practice, so I'd encourage you to align and re-align your cartridge several times. The more often you do it the better you'll get at it.

As Markd51 said:

1. Align the sight line to the tonearm pivot using a piece of thread (WAY more accurate than just looking down the line).

2. Place the stylus on the outer grid and square the CANTILEVER to the grid. (Ignore the cartridge body). If you do this "perfectly", the inner grid becomes theoretically superfluous.

3. Move the protractor and recheck cantilever squareness with the stylus on the inner grid. (Just a double check).

4. If it's not square, iterate back and forth between grids until it's square on both.

Doug
No problem Mark. It was Frank Schroeder who taught me the string trick. We all learn from each other!
A laser leveller does work but a thread (not "string", I misspoke) is actually more accurate - thanks to the parallax effect. Sometimes simplest is best. :-)

One thing we ought to have asked is, what tonearm/turntable are you planning to use this protractor with? If your rig isn't Baerwald compatible then this whole discussion is moot.
Rega arms are not designed for Baerwald alignment. The standard Rega mounting distance of 222mm puts the arm too far from the TT spindle for some cartridges to reach both Baerwald null points. You'd have to move the cartridge farther forward than the headshell slots allow.

If you have a moveable armboard the fix is simple however. Just mount the arm at 219.5-220mm. At that distance any cartridge should reach the Baerwald points without difficulty. I did this successfully with an OL (Rega mount) arm on a Teres (pivoting arm board) and so have many others.

Alternatively, you could use a Rega protractor and mount the arm at the standard dimension. Baerwald alignment tends to produce lower tracing distortion than Rega alignment, however, so that's probably the preferable method.