Hi Michel - I have a pair of BAT VK200 which BAT converted to mono blocks. I replaced the internal ("rail") fuses with HiFi Tuning Supreme fuses to very good effect. The external fuse, which I also upgraded did not have nearly as much of an improvement. One thing to keep in mind - BAT amps use very good caps, so let your amp unplugged overnight before changing the rail fuses - otherwise you might get a REALLY bad shock.
