Tube dampers/coolers effect on preamp sound?

Have you tried calling Audio Research direct or an ARC dealer?

Replace the cheap tube Sockets with Teflon units and you will get the best improvement.

For those who have bottom getters like the RCA smoked glass VT-231 and Sylvania 6SN7GT and are using Herbies tube dampers, you might try moving the damper all the way down the glass to where the damper just touches the base. I recently found that a second Herbies damper attached directly to the tube base was quite efficacious.