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 all, to my knowledge the 9" and 12" denomination was introduced by SME with their original 3009 and 3012 tonearms (hence the names...3009 and 3012). Ever since then 9" and 12" is used to describe tonearms which do have an effective length around the 9" or 12" figure.
But they all do differ in their effective length - some are very close, hardly any is exactly the same as another.
Take a few 12" tonearms as example:

- SME 3012 - 307,34 mm
- MAX-282 - 282 mm
- FR-66s - 307 mm
- SAEC-506/30 - 295 mm

these are all named 12"-tonearms. 12" is 304.8 mm - so none of the above mentioned tonearms is really 12" in effective length.
Only the SME 3012 and the FR-66s are close to that measure. Same for the 9" SME 3009 which is VERY close with its 229 mm (the later 3009R has 231,80 mm.......).
Well - we can alter the effective length of any given pivot tonearm.
And we do.
We can do so easy and - in a certain and narrow range. We do this when we adjust/change overhang (and in the same procedure the related offset...) to achive for instance Baerwald or Loefgren based geometry. We had that topic already back in the thread about the "Oldskool tonearms".
Take again the Graham alignment tool.......... here you have a very good and clear example.
The base (= mounting distance) isn't moved at all. The change is done at the headshell by different overhang and offset.
The mounting distance is still fixed. You change overhang and offset to adjust to different zero-error points - not the mounting distance (at least..... you shouldn't....) - not the mounting distance P-S.
The mounting distance is the 1st and basic parameter of the calculation of any pivot bearing tonearm.
Dear friends: Anyone of you can corroborate what I posted here:

http://www.ispexperts.com/BaerwaldLofgren1.xls

Dertonarm: where can we corroborate what you posted?

Regards and enjoy the music.
Raul.
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.