I had a VPI Magic Brick way back when. I tried it on all sorts of things, preamps, power amps, CD players, FM tuner, and in lots of different locations on top of each component, and I never found a single instance where it improved the sound. The sound changed certainly but never for the better. Once your ears identify the Brick's colorations, they become easy to hear with each piece of equipment. As I recall, the colorations were a distant or recessed midrange and a steely, edgy quality in the treble. Why anyone would want those colorations is beyond me. My happiest day with the VPI Brick was the day I sold it.