For the last few years, I've been developing a system for measuring, calculating and printing out alignment protractors for cartridge / tonearm pairs. This has proved to be a great help when setting up new equipment. It's also helped me to learn a bit more about cartridge / tonearm alignments, and how they work together.
The problem with cartridge alignment is that the only way to determine the level of accuracy you need (or want) is to trial and error. There are no fully automatic alignment tools out there. The only way to determine the right tonearm pivot position is to make a tonearm measurement, or measure the distance between the cartridge and the tonearm mounting point. This distance is known as the pivot to spindle distance. It is usually printed on the tonearm.
The tonearm pivot to spindle distance is the distance between the pivot point on the tonearm and the spindle point on the cartridge. In many cases this point is perfectly aligned with the cartridge's stylus tip, and if that is the case there is no need to adjust for offset and null lines.
The Arc Protractor Generator is a work in progress. If you have any suggestions or feedback, please feel free to send me an email, or leave a comment below. If you have any downloads of your own, please put them in the comments section, I'd love to see them!
In order for these protractors to actually provide good results, they need to be adjusted to each cartridge prior to their use. I like to use a Beurer M4VTH (marking 4, wood, veneer, thumbtack, zero hour) to set the alignments, in addition to the factory setting. If you are using wood as the mounting surface, use a Baerwald type protractor first to set the alignments before replacing it with a KWillis type protractor.
The QRP cartridge is a Sengl type with a four inch carriage arm and a full length housing. This means it's a thin neck cartridge, so some care is needed when measuring the neck diameter. The bottom of the neck is actually at the centre of the groove, not the bottom of the groove. The neck diameter should be measured at the point where the neck meets the groove and not where it is just starting to taper. Under normal testing conditions, this is about 30mm from the centreline of the groove.
To try it out, you will need to insert the resistor, phone line and crimp terminal into the appropriate holes on your protractor. You will also need to insert your tonearm (or a dummy arm) into the appropriate holes on your protractor. 827ec27edc