How to use cartridge alignment protractor with mirror

Bought this from Amazon but not sure how to use it:

https://www.amazon.com/Turntable-Cartridge-Stylus-Alignment-Protractor/dp/B005KR15HU/

1) What is the purpose of the mirror? It seems to confuse me.
2) The back side has two sets of instructions ( see attached image ), CA-001 and CA-002. Not sure what is the difference and which to use.

 

Just follow the instructions in the CA-001 section, you just have to go back and forth between the inner and outer grid, adjusting the overhang and offset until you are aligned with the grids at both points, with the stylus centered on the bullseye ... the mirror just helps you to see the cantilever and cartridge body reflections from above so adds some accuracy... most people tend to prefer using an arc protractor since it separates the overhang and offset adjustments, but if you are careful, something like this can get you close (most would say close enough) ...

 

I say use the CA-002 instructions, they are more clear. But either set is technically correct to use that protractor.

The mirror is for you to check that your cartridge is perfectly perpendicular (up and down) on the record. If the cart was slightly tilted, the mirror would help reveal that since the reflection would not line up.

I think the CA-001 instructions are for a protractor that has a curved line so the protractor would not need to be rotated. The 002 instructions for a protractor that has a straight line where you rotate the protractor a bit. But either instructions will technically work for either type.

 

OK, just in case it is not clear (and dismiss this if so, just trying to make sure you understand things that sometimes confuse people). When you align the cartridge to the first outer point, do not assume you just lift the whole arm in and the stylus should line up on the second point. It cannot. You must move the protractor so that the stylus can meet the 'bulls-eye' as they call it (by physical necessity, the arm will traverse an arc across the record, not a straight line, so the protractor will have to shift accordingly between measurements). I've known people to get stuck on this as the instructions are often vague.

When you land the stylus on the 'bull', you need to crouch down and get your eyes at platter level. Then look straight at the the cantilever of the cartridge. Does it look like it's lining up with the groove or is it leaning left or right? THIS is where the mirror can help as it amplifies any angular difference to show you. If you align the cantilever correctly and the stylus can land in the bull at both points (remembering that the protractor will move between measuring both points) you likely have things in a good spot. With the mirror, the cantilever and it's reflection should look straight. It takes a bit of practice cos your eye position can throw things off but when you see it, you'll know (I hate that but it's true). Hope this does not confuse more than it helps!

 

The mirror assists with parallax. You have 2 eyes, so your perception of parallel lines tends to converge because you eyes are offset from each other. This is great for depth perception, but this isn't exactly desirable when you align things. The mirror will reflect the lines inscribes/marked on the surface of the protractor. When you align the stylus the reflected markings should align to the surface markings. Properly done, the reflected image is aligned to the surface markings, then you adjust the alignment of the stylus to the aligned reflected and reflection markings. All three things align. This is particularly helpful with an elliptical stylus where the profile is thinner from side to side than front to back. I'm not at all sure a mirrored protractor is helpful with a conical/spherical stylus where this isn't the case. If you can't get things to line up, close an eye, or better yet, use a jeweler's loupe. The lens will not only give you magnification, it will only allow a single "in-focus" viewing of the stylus and markings, so parallax is nullified.

Aside from this, the protractor is used the same as any other opaque or paper protractor.

 

I don't think I have come accross a protractor with curved lines. Can you share a link to one?

 

I am confused on the terminology, overhang and offset? Are these basically saying the cartridge needs to be "rotated and translated" till aligned at both points? Or does one have to first rotate then translate ( move along axis of tonearm )?

 

Well, the internet is full of fairly easy to understand guides and pictures on cartridge alignment, such as the one below ...

 

http://i.imgur.com/bSZZlyx.jpg

Cartridge protractor question

and (different):

 

Are you sure CA-001 make sense for this tool? I have read it a dozen times and it makes no sense what they are saying, i.e "compare angle at A with B".. Which angle are they referring to..

 

The offset angle. If it is changing as you move back and forth between the grids, from A to B, they are giving you guidance on which way to adjust the overhang, more or less (more overhang being to move cartridge further from tonearm pivot). Basically both sections say the same thing, the CA-002 just has more detail, but they are interchangeable, there is only one way to use the protractor.

 

"Overhang" means the distance from the spindle center point to the stylus tip with the cart over the spindle.

It does make sense if you follow it exactly, but it is confusing and not meant for the straight line protractor type that you rotate. So ignore the 001 instructions and use the 002 directions.
Both instructions are basically literally the same if followed exactly, but written for the two different types of protractors, and will give the same result.

 

I may be mistaken, so others are welcome to correct me, but I look at the instructions and see a standard 2 point protractor with Baerwald, or at least very close to Baerwald null points.

As I see it, the CA-002 instructions would apply if the tonearm geometry is established for Baerwald alignment. Note that those instructions result in a cartridge that is sitting square in the headshell.

On the other hand, if the tonearm being used has a geometry that is appropriate for Lofgren, Stevenson, Rega, etc. or any other alignment, the cartridge is not going to sit square in the headshell and is probably going to need to be twisted to achieve the correct offset angle to align to the grids. Hence, the CA-001 instructions.

 

Both the 001 and 002 do note it may be necessary to "twist" the cart.

 

If you know the overhang for your turntable and its original stock arm, start with the overhang - get the stylus tip at that distance from the center point of the spindle, first. Then using the protractor will be much faster and easier to fine tune - which can result in moving the cart a bit closer or farther from the arm pivot and putting a slight twist on the cart in relation to the headshell.

 

True. I'm so used to using an arc protractor and aligning to null points other than spec'd by the tonearm manufacturer with very different offsets that I looked at this and that is what I read into it. Plus I'm old and tired today .

What threw me off is the 002 instructions state specifically that the cartridge will be square in the headshell and the 001 instructions do not. Can't really see the need for the 001 instructions in this case; they do more harm than good by confusing people.