Yeah, I had these under my tube monos (Cary 300SE's) for a couple of years. I took a lot of care with vibration control. The amps were on top of 3" thick hardwood blocks I made, which were in turn supported by cones. The black raviolis sat between the amps and the wood blocks. The tubes all had dampers on them. The net effect was very positive. I put the raviolis in last and did notice an incremental improvement. I've changed my whole setup now and they are just sitting around ... forgot about them till you brought it up! Hope that helps.
