I was reading a thread on AA about this tweak and became intrigued. Folks over at AA have reported positive results, so I figured what heck, and ordered the free samples. They came all the way from New Zealand and the manufacturer did not even ask for postage. Apparently he's trying to get the word out and figures getting people who belong to various audio forums to try them is a good way to reach critical mass.
Anyway, I got around to placing them in one of the locations recommended by the manufacturer, which is on the positive speaker terminals on the back of my power amp. The test CD was Bonnie Raitt, Silver Linings, which is well known to me; a good recording with great tunes.
Played the first cut, and then placed the Black Discus per above. Not a night and day difference, but there was definite improvement in detail and timbre of instruments, transients and her voice. The soundstage deepened front to back, stayed the same laterally. Background instruments were slightly more prominent and easier to hear especially in busy passages. The music seemed to be more enhanced and yet smoother, more engaging.
The free samples I received were two quarter sized discs that are smaller in diameter and thinner than the recommended ones for the speaker terminals. Presumably the appropriate larger ones will produce more of an effect. Among his placement recommendations are on the top of transformers in pre and power amps, so I ordered 4 of his largest ones (aka Cupcakes) last night so I can cover trannies in both and the speaker terminals.
His website is here, which includes instructions on how to get your freebies: http://www.madscientist-audio.com/
You won't find any info on what they're made of, or how they're supposed to work as he has a patent pending. Once I get the product and spend some time with it I'll update this.