Tracking error distortion audibility


I recently unpacked my turntable from a couple of years of storage. It still sounds very good. Several times during playback of the first few albums I literally jumped from my chair to see which track was playing as it sounded so great. After a while I realized the "great" sound was always at one of the "null" points. They seem to occur at the approximately the proper place (about 125mm from spindle) and near the lead out groove. Questions:
Is this common? I have improved the resolution of my system since the table's been in storage but I don't remember hearing this before.
All others geometric sources of alignment error not defined by the null points (VTA, azimuth etc.) are essentially constant through out the arc correct? If so they should cancel out. I assume the remedy is a linear tracking arm but I am surprised at how obviously better the sound is at these two points.
Table - AR ES-1, Arm - Sumiko MMT, Cart. - Benz Glider, Pre - Audible Illusions, Speakers - Innersound electrostatic hybrid
Do linear arms really sound as good across the whole record as I hear at only the nulls with my set-up?
feathed
Dear Dertonarm: I'm not talking on the name of the tonearms model but real: 12",11", 10" or 9" ( inches ) effective length.

Regards and enjoy the music.
raul.
Dear friends: I think that the Graham is a real 9"=228.60mm tonearm, well here are the results on Baerwald:

offset angular: 24.128 degrees; overhang: 18.173 mm and P to S: 210.43mm

Lofgren B.

offset angular: 24.128 degrees; overhang: 18.690mm and P to S: 209.91

As you can see the offset is the same and the other two parameters are different ( including the pivot to spindle distance. ) where the effective length is the same.

regards and enjoy the music.
Raul.
If you can't take it ( the Baerwald/lofgren calculations ) on the link I posted please email me and I send to you.

Through this " page "/calculator you can " play " with your tonearm-cartridge set-up changing parameters in a " safe " and precise way.

Regards and enjoy the music.
Raul.
Dear friends: That " calculator " give us many interesting " numbers ", example: the average distortion in a 12" tonerm is 0.3105% and in a 10" is 0.3815%, do you think can we hear the difference?

You can find out that tracking distortion/tracking error at any place/groove position in the LP and can compare between different tonearm lengths where you can ask: can/could I detect those distortion differences? are there real advantages on long tonearms?

This is only an example, there are more information on the whole subject including null points calculations.

I hope you can have fun with it.

Regards and enjoy the music.
Raul.
Dear Dertonarm: Please forget it what I ask you, I don't need that you corroborate nothing at all.

regards and enjoy the music.
Raul.