Please be aware that the Furutech rhodium fuses require a very long time to burn in (around 200-300 hours). After 10 hours, you are already in the "painful" stage. Keep the fuse in the preamp for another 10-15 days and then do critical listening. It will actually go through several changes.
That being said, I think a 4A fuse is probably way too much for a preamp. I would not put in more than a 2A, but I don't know your current preamp model.
That being said, I think a 4A fuse is probably way too much for a preamp. I would not put in more than a 2A, but I don't know your current preamp model.