@guyt The easiest way is to simply test the sound quality in each direction. As others have stated, this doesn’t take long at all, the fuse doesn’t need to be fully broken in, and the preference will be clear to you.
+1 to
@davidpritchard for his very helpful post, copied below:
I have tested the basic ceramic fuse that comes stock in the Pass Labs amplifiers that use a fuse. The fuse does exhibit directionally, but it is not a striking difference. The audiophile fuses I have tried have a greater change in sound depending in the direction they are installed.
The Synergistic Research Blue and Orange fuses should be installed with the "S" closest to the hot side of the fuse holder and the "R" closest to the Neutral side of the fuse holder. There are at least two ways to decide which side is the hot side. One is to buy an inexpensive circuit tester screwdriver. When touching a hot connection the screwdriver will exhibit a bright light. The less reliable method is to look at the equipment and trace the direction the current flows. This is straight forward when the fuse is located as part of the inlet for the power cord. Easy to see which side is Hot and which side is neutral. At other fuse locations current direction may not be obvious.The "S" of the Synergistic Research label should be closest to the Hot side.
Of course the other approach is to just listen to music (thirty seconds is plenty) , and keep the fuse in place where the sound is better. This can be done on first installation. You do not need to break in a fuse for 10 days and then test for optimum direction. I have done that rather tedious experiment. No need to repeat that approach.
David Pritchard
