Bgordon- Try the AC line fuse first, and if your system/room/ears resolve a difference(that you like), then try the DC rail fuses. Any improvements that one can make in the power supply of their amplifiers should provide a sonic gain. The power supply is what drives your speakers, whether modulated by transistors or tubes, as directed by the music signal. That's the fuction(power supplies) for which Hi-Fi Tuning, Isoclean and Furutech fuses were designed, and hence- where they will work best. Of course they're not just for power amps, but any audio gear with a power supply.