Same as Ozzy, too much was not a good thing for my system either.
The tweak worked awesome with my CD player (or what I'm using as a CD Player, PS 1), and my Oppo 980 DVD player, improved, but to a lesser extent, my DAC, but killed the sonics on my tube integraed (PrimaLuna PL2).
I have an aftermarket PC on my amp and stock cords on my other gear (don't know if that makes a difference).
I also have the couplers on both ends of the digital gear.
On the amp, it flattened voices and made the high frequencies "tizzy".. I only had the coupler on the female/amp end but it was a very noticeable degradation of sound.
Either way, great tweak.. best $2.39 CDN I've ever spent. I can't believed it worked.
I also make a little sleeve with Duct tape around a little bubble wrap to create a snug fit and have the couplers tight up against the chassis..
Wondering if it puttin a coupler on my cheap power conditioner would make a difference?