TONEARM DAMPING : DAMPED OR NOT ? ? USELESS ? ? WELCOMED ? ?

Oh I guess I should have stated that an "O"scope was used in all my tests.  Really this tool is essential for these kinds of tests to be useful and repeatable.

Raul,
Congratulations for picking another fascinating and controversial topic for discussion.  I intended to sit it out because there is no single solution to your puzzle, but decided to chime in with my opinion based on some measurements and experiences with two different set ups.  First set up:  Arm, SME Series III.  Cartridge, Shure V15 Type V MR.  Test Record used, Shure ERA IV.  I know you are aware, but for the record this was a high compliance cartridge and a low mass tonearm, considered state of the art back in the day by Gordon Holt among many others.  It still sounds very good mounted on a VPI HW-19.  Anyway in setting it up first without damping fluid in the trough, and then with damping fluid in the trough there was very little difference in tracking ability leaving the VTF at a nominal 1 gram with the little damped brush down as per Shure's instructions.   With the brush up, the damping fluid in the tray might have made a slight difference, but really not enough to get excited about in my opinion.   What did make a clear difference, however, was that little brush, stabilizing the arm and improving tracking in all tests.
Sometime later I played with fluid levels in the trough and found that it made no discernible difference until too much fluid was added.  I determined too much fluid to be approximately half full for the Series III trough.  Too much fluid made the sound thicker somehow and noisier.
Second set up, I added a damping trough from KAB to my SL1200GAE, a SoundSmith Hyperion made no audible difference, although using the Ortofon Test Record, it did track a bit better.  I have not experimented with fluid levels on this set up, but left the level below half full.
This experience is not enough to draw broad conclusions from, although I believe Shure demonstrated conclusively that a damped brush on the end of any tonearm can stabilize the arm and aid tracking.  I will go further and opine that this would be so for high and low compliance cantilevers, low to high mass tonearms, and would be particularly efficacious as tonearm length increases.  Again, for emphasis, that is my opinion only and is not based on experimentation.

Bill

Raul,
While you seem satisfied with you methodology, I encourage you to try and borrow an "O"scope because I am sure you would like it.  When the arm and cartridge are optimally set up and playing a high velocity groove on a test record right on the edge of the ability to trace the tone, in addition to being able to hear the edginess as the stylus barely maintains contact with the groove, you will be able to see the trace and any mistracking on the scope.  So you have two data points, auditory and visual.  In many cases it is possible to fine tune the set up even further using the trace on the scope even after all seems ok to the ear.  Conversely, in my experience it has never been possible to beat the trace on the scope just using the ear.  But of course you must have access to a scope and spend time experimenting to see what I mean.  Also, the scope saves time in that you will get the optimum result faster and it will always be repeatable.  Try it, you'll like it.  I think, too, that once you have tried this set up method, you would then continue to confirm your results with your current methodology.  Please do not assume that I am finding fault with what you are currently doing.  Not at all.

Bill

Lewm, Your point about the complexity of a musical wave form is well taken, which is why it is important to follow up by listening to music as Raul has explained.  This is a very enlightening discussion because it underlines the importance of keeping an open mind and that there is value in using every available resource to optimize the set up of our record playing equipment.  And of course things change over time, so it is necessary to check, realign, re-check etc. to get the best results.  It is worth it, though, at least to me.  I find analog more challenging and more rewarding that digital equipment that sits gathering dust most of the time.

Bill