@noromance I have been fortunate to share in a variety of demonstrations from Idler Drives, I have also heard Thorens Models and the Garrard 301, but these are too long ago in the past to make a recollection of.
In the earlier post, I should have added a Corian (owned) and Polybentonite Resin Plinth, to the list of Plinths I have been demonstrated in use on a Idler Drive.
There is at present, a move toward Densified Wood in certain communities, where the board is to be used as a Plinth Material for Idler Drives and the users of Plinths produced from Board such as the Brand Panzerholz or Permali are making very positive reports.
I own boards in both Densified Wood Brands but have these materials at present reserved for another Model of TT and Plinth Design.
My most recent experience of being demonstrated a Idler Drive is a Garrard 401 that has been mounted in a Plinth with a Top Plate produced from a Side and Top Pressure Compressed Bamboo Board. When Bamboo is produced using this method, the Damping Factor is 0.200.
The Damping Factor of Permali is 0.688, Panzerholz is 0.599 and Polybentonite Resin is 0.618, the resin is a common 'go to' material for a Idler Drive, it is Massey and as far as I know, it does not dissipate energy as efficiently as a Densified Wood or the lesser efficient Compressed Bamboo.
The Bamboo Top Plate Mounted 401 > Origin Live ' Illustrious ' Tonearm > Sumiko Pearwood Cart' has had Isoacoustic Footers and has been mounted on a Sub Plinth assembly produced from my owned Panzerholz Board and AT-666 Footers.
The demonstration proved to be quite attractive and memorable, the 401 had recently replaced a SME 20/12 > SME V, the group in attendance and the 401 owner were not missing the sold of SME equipment that were all quite familiar with.
Through a friend I have listened to various works undertaken on a standard Lenco GL 75 Bearing and their methods adopted to rigidly secure the Bearing Housing from flexion.
I have had my own PTP Solid Nine used a comparison to the friends undertaken works, with the outcome being assessed that a standard Lenco with selected methods adopted, can sound almost identical to a PTP, possibly only the Plinth Materials > Tonearm > Cart in use being the main influences on the differences detected.
Shortly before the Covid Lockdowns, I would have suggested it is impossible from my experiences to pick an absolute preferred TT, as their were too many variables in the demonstrations, i.e, Plinth Materials, Tonearm, Cart's and TT Mounting Methods.
This changed just prior to the Lock Down Period, the friend with the GL75's had received a Extended Length SPH Bearing, it was supplied as a Special Version, as my friend had encouraged the Bearing producer to have a Spindle made that was a Composite design, the Spindle has Metal within the housing and a Ebony Wood is the attached Part of the Spindle that is visible above the Bearing Housing.
I also know the Thrust Pad was changed and the Lubrication in use was said to be working as Hydrodynamic. Being very familiar with this persons work and different concepts, as well as having my own PTP with the PTP bearing used as a comparison to their earlier work undertaken, I was not expecting too much of a margin of change.
The version of SPH Bearing in use attached to a GL75 with a Speed Controller, was the most indelible memory I have from any experience in recent years, it was a very gathered and exact presentation, that was the most attractive of many recollections and was being perceived as being noticeably improved over prior experiences.