cones under preamp

Hi folks, whenever I put cones (ebony wood or aluminium) under my preamp, there is an audible change to the sound. Whether this change is an improvement or not, I'm not sure. Although this tweak adds more detail (and probably also a tad more spaciousness) to the sound, I also hear a bit of thinning out of the lower mids and a shift towards the upper mids and bass. Soundstage is pushed further back. The bass becomes more prominent, but sounds as if it is separated from the rest. It's as if there is a "hole" in the midrange and the sound loses some immediacy. This phenomenon can also be heard when I put the cones under my CD-transport or DAC. Is this a well known phenomenon with cones in general?
You might want to try repositioning the speakers with the cones under the preamp. I just personally learned that a tweak can alter the sound so much that you can't take your current speaker position for granted.

I have had some real lousy results with cones, misc rubber
feet, etc. under my Sonic Frontiers hybrid (one tube) preamp. Be VERY careful here, as my two years of experimenting did show it is far easier to make things worse than better, under a preamp particularly.
Out shopping, I saw these "pyramid-like" stones, smooth polished....four 3" sides at bottom, all coming to a single point at the top. Something about it just looked promising, so I bought four and tried them....the best I have found so far for my preamp. By the way, all four cost a total of 4 bucks...I found them at the dollar store!
Good luck....keep experimenting, in my opinion.
Soundstage being pushed back is a good sign. That means you're reducing glarte/vibration in the system.

I agree the cones might be revealling weaknesses in speaker placement.