Tom,
I was just pointed to this thread. There's too much good inforamtion to sift through at the moment, but based on the names of the posters, along with a quick scan, it looks as if you've received good advice.
I likely missed some of the finer points, but here are some thoughts.
1. Same problem with all sources?
Do you get the same pumping when playing CD? I assume this isn't the case, but it needs asking
2. Changes in stands/shelves.
This strategy seems to be pointing you in the right direction. No time to comment on the apparent disconnect of suspending an unsuspended turntable.
The key point to mention however is, that with Vibraplanes, microscope tables, etc., the entire 'table is suspended - the critical relationship between drive system and platter is still intact.
Maintaining this fixed relationship between drive system and platter/bearing is key to the success of an unsuspended design, and placing the entire assembly on an air table is consistent with the design goals.
My expereience of a Townsend Seismic Sink on my turntables was essentially a whole lot of trouble for no improvement over a *well* *implemented* sandbox design.
I've never met Sorbothene that I wanted in the same zip code as my hi-fi, but I can't profess to having tried every last permutation. Let's just say that it's the last place I'd look for answers.
3. Cartridge.
Don't rule out the cartridge, just because the Tri-Planar/Universe is a ubiquitous and compatible combination. You might have a sample that's aging differently. Mount another cartridge. You've tried enough differnt things to not want to overlook this.
4. Oil.
It wouldn't hurt to re-lube as you've been running your rig for something like 3-4 years. I don't expect any changes here.
I'll try to work through this rather long thread as time permits, but don't hesitate to call me.
Cheers,
Thom @ Galibier
