garrard vs clearaudio innovation

Pretty darn happy with my 401 in 40lb birch and curly maple plinth with Micro Seiki ma505ls arm.
As far as I am aware it is stock idler, bearing and platter. Although all cleaned up, lubed and fresh setup.
Sits on my rack on solid tiled concrete floor.
No rumble I have ever heard even with ml Dynamo sub.

Last time I looked the Artisan Fidelity platter, bearing and idler upgrade ran out to $3900 parts only.
Not going to happen in my lifetime......

Well uberwaltz, you have an exceptional one I guess. The three that I have been witness to have had that problem. None of these people had subwoofers but if you watched their woofer cones at volume they were dancing around like man men, probably almost bottoming out.
Try turning up the volume and play a dead groove if you have one and watch what the woofer cone does. With a quiet table you will just see a little motion with a noisy one the cone will be dancing.
Back then their solution to the problem was a rumble filter. All the old high end preamps had one. 

Then after the AR turntable popularized belt drives and with the invention of electronically controlled motors and direct drive tables there was no longer a need for idler wheels to change speed. Idler wheels and rumble filters disappeared from the market. I'm all for nostalgia but if I ever get another TD 124 it will be for display only.

Mike
I do not have any woofer cones to dance.
Maggie's in my system.
Maybe that is the key here?

IF there is low frequency rumble, that fact that you don't have conventional woofers will only save you from having to observe the cone dance that might otherwise result.  However, the rumble would still eat up amplifier energy and possibly cause distortion in upper frequencies.  I say "if".  I don't necessarily agree that the 301/401 cannot be modified to eliminate or at least ameliorate that problem, without going all the way to the Artisan Fidelity set of solutions.