How to Use Double-Point Alignment Protractors

any older tonearms used double-point protractors that require a slightly different approach to single-point devices. These are not referenced to the tonearm pivot but to the two different grids on the protractor itself. Here are step-by-step instructions for our preferred approach to optimizing alignment with these tools.

1. Immobilize the platter to stop it turning, using a small rubber wedge or a blob of Blu-Tack or similar, if you haven’t done so already. Likewise, ensure that the bias adjustment is set to zero.

2. Place the protractor over the spindle and place the outer grid (farthest from the spindle) so that the stylus drops onto it. Now, adjust the position of the cartridge so that the cantilever is parallel to the grid on the protractor and parallel to the slots in the headshell (Note: the cantilever parallel to the slots, not the cartridge body parallel to the slots).

   Hint: If the cantilever tip is pointing toward the center of the record, then the cartridge needs to move toward the front of the slots. If it is pointing away, it needs to move back.

3. Once you have the cartridge aligned so that the tip is at the center of the grid and the cantilever is parallel with both the slots and the longitudinal lines on the grid, swap it to the inner grid. This will mean lifting the 'arm and then (generally) rotating the protractor clockwise on the platter.

   Just as above, if the cantilever tip in the new position is pointing toward the center of the record, then the cartridge needs to move toward the front of the slots. If it is pointing away, it needs to move back. Don’t adjust it yet! First return to the outer grid, move the cartridge as indicated and recheck on the inner grid. Keep going until the cantilever is parallel/parallel in both positions. Each time you swap grids, you will have to reposition the protractor and as you adjust the cartridge you will gradually reduce the alignment error. The key is to make sure that you have the cartridge precisely on the center of the grid each time. Eventually you will achieve a position such that the cantilever is perfectly parallel in both the inner and outer grid positions.

4. Once you have the cartridge positioned, recheck the downforce and adjust.

5. Recheck the 'arm height and adjust if necessary.

6. Recheck the alignment to make sure that it is still good, and repeat the whole process if necessary.

7. Finally, set the bias force. This counteracts the tendency of the curved groove wall to push the cartridge towards the center of the record, thus keeping the cantilever centered above the groove. The starting point     for this is a value equal to the tracking force, although many bias systems are uncalibrated, relying on magnetic forces, falling weight or springs/dials. In either case, the way to check the setting is by watching the stylus settle into the groove from the front. With the platter turning, use the cueing device to drop the stylus halfway across the record. The cartridge should settle dead straight, smoothly, without wobbling or lurching inward or outward. If it moves out, increase the bias and vice versa if it moves in. If in doubt, tend towards lower bias values as they generally sound better.

If all this sounds like an endless round of set, check, set and check again -- that’s because it is. Setting up a cartridge really isn’t difficult, especially if you make sure you have all the tools and sufficient light before you start. What it is, is repetitive and painstaking. The more careful you are, the better the results and the better your record player will sound.