Tube dampers/coolers effect on preamp sound?

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.

Yep, I added some Audio Research rubber band-like tube dampers to my Manley Steelhead phono preamp and I heard a tightening of the sound, especially in the bass, and improvement in dynamics. It didn't make the difference other tweaks such as Audio Prism cables or Kemp Elektroniks plugs made, but still a very cost-effective tweak.

I did not like the effect with my Audio Horizons Preamp (lost openness and aliveness) though it did stop microphonics