VTA and HTA overhang

Peterayer,

I don't quite understand your triangle illustration, but you seem to be making an assertion that as you move the arm up or down, you pull the stylus in or out. I just don't think this is correct. Perhaps large VTA adjustments might result in stylus displacement, but I just don't see why small changes in VTA should result in overhang changes. The simplest illustration I can think of is lifting a fork that is placed teeth down on a flat surface. You can certainly move the back of the fork up and down without bringing the teeth on or out; you only change the angle at which the teeth and the surface interface.

If you were correct, any tonearm designer who offers VTA adjustment on the fly would not understand the basics of cartridge alignment, which is absurd. My guess is you're doing something else to the alignment as you adjust the VTA that would explain the overhang changes you noticed.

Theo, You can refer to my system page. I have an SME 12" arm. As such, it requires a greater increase or decrease in VTA to effect the SRA than it would with a 9" arm. Similarly, the offset angle at the headshell is less than with a shorter arm, so skating force is not as great. Also, SRA changes during warped records are not as great.

Actusreus, I believe you are mistaken. As mofimadness pointed out above, changes in VTF, even very slight, do change overhang and thus alignment as the effective length of the system (pivot point to stylus) is altered as the cantilever changes angle due to the greater or lesser tracking force. Your fork analogy is a good one. As you raise the end of the fork the teeth will indeed move in or out. Remember, your lifting hand must move vertically only. Imagine a very short fork and movement up or down of one inch.

Even though a small VTA adjustment only changes overhang very slightly, and it may not be audible to all, overhang does indeed change, changing cartridge alignment. I believe this is a geometric fact.

I'd like to hear from those who change VTA for different LPs if and how they account for the change in overhang. Mofinmadness understands the issue. I'm trying to learn if it is more theoretical than practical.

Good topic Peter. I have noticed this effect as well.

Actusreus, your fork analogy does not work. If you could lift the rear of the fork straight up without letting it move forward as you lift it would pull the front back. This is quite easy to test with your tonearm. Just setup your alignment protractor and play with VTA. It's easy to see.

Now as long as you only make small changes in VTA it may not be necessary to reset your alignment. It depends on how anal you want to be.

When setting up a cartridge I rough in the weight first then rough in the SRA. That way when you set the alignment it won't change as much when you dial in VTF and VTA. It does make sense to readjust overhang as a last step. If you change VTF and/or VTA significantly afterward you should also reset overhang. Most people don't take that into account though.

Sean

Peter, What happens when you use a taller record than the one you used to set your alignment? A taller record will push the stylus forward a bit. By adjusting VTA up the correct amount you compensate for that. So adjusting VTA for different height records preserves the correct overhang as long as you adjust it the correct amount.

Sounds like you just made a case for VTA adjustment not against it. ;0)

Unfortunately there is no way to account for record warps as they will surely change overhang as well. Even clamping and or vacuum hold down will not remove all the warps.

Sean

I'd rather listen to music and compromise on "ideal playback" than adjust my tonearms for every record.

Life's too short IMO.