Sorry to resurrect an old thread but I am astonished by what the free black discus nano's did in my system. When I received them as a free gift with my contact enhancer I looked at them and laughed. They sat on my desk for months. They are hard to take serious. One afternoon I thought "what the heck, it only takes a matter of seconds to try". So I placed them on the speaker cables as they exit the amp. Unbelievable improvement. Music was less garbled, less fuzzy, cleaner, more concise without losing musicality. I found it's best to experiment with placement. The best balance for my system was actually on the speaker cables where they connect at the speaker.
I'm looking forward to further experimentation.