Tube dampers/coolers effect on preamp sound?

I use Herbie's Tube Dampers on all of my tube gear. I wouldn't say it's a profound difference, but well worth the asking price. It's a pretty cheap tweek that works well...IMHO.

Thanks MOFI. Can you describe the improvement at all?

I also use Herbie's Tube Dampers in my preamp (4 tubes) and the result was a tighter bass.

I have heard one person say that they heard a reduction in openness and soundstage when using a damper. Any opinions of this?

"I have heard one person say that they heard a reduction in openness and soundstage when using a damper. Any opinions of this?"

Results may vary on each system; I haven't heard, that but I know from experience that postion of the damper on the glass tube will produce a different effect. Herbie recommends placement 1/3 down the tube.
Why not google Herbie's audio lab... there is a Q & A section.