I bought an Isoclean fuse to compare against the HiFi Tuning fuse. I seriously doubted there would be any difference.
Last night I sat down and spent three hours listening to several tracks twice - first time with one fuse in, second time with the other. I jotted down a few notes from time to time. Can you guess the results?
That's right - the HiFi Tuning fuse won almost across the board. For jazz and classical I preferred the HiFi Tuning fuse because everything seemed cleaner, airier, and just more "real." The Isoclean fuse had more-defined imaging, but I felt some wind instruments, chiefly alto and tenor sax, sounded ever-so-slightly colored. The only place I might have preferred the Isoclean was with hard rock.
Just my two cents, but I thought my experience was interesting in light of this thread.
As an aside, there's a thread on audiocircle where some folks in Denver recently tested various fuses, and found a silver-plated fuse that they liked better than the HiFi Tuning fuse. You can find the thread here: http://www.audiocircle.com/circles/viewtopic.php?t=28274
Howard