I stumbled upon these couple of years ago. I was skeptical to try these but our never quest for high fidelity leads us into trying stuff that sometimes borderline voodoo!
From experience we all know effective vibration control just as important as speaker placement and clean power supply. Since I am already using RCA caps to prevent the EMI/RF interferences entering my system, I thought why not give these RCA plugs give it a try.
After reading few articles, they were designed to control vibration and resonance on the circuit board. They look like any other RCA plugs except that center pin is made of some kind of dense, nonconducting felt. The rest of the plug is metal covered with soft black material.
Well, let’s insert them and see what happens. I let them stay in my system for 50 hours. During A/B test, I heard quieter background, the music sounded bit more lively and less colored. Whatever they were doing, I was beginning to appreciate the subtle but noticeable differences in sound. I see no reason to remove them so they stayed in my system.