I am way late to this game! I don't yet believe in fuses making a difference, but I have been wrong about cables, capacitors, etc., so I am not going to say that they can't, I just seriously question it. As for your by-pass caps, there is no way to argue that quieter DC doesn't improve sound in my experience, so if a capacitor is a better filter, it can absolutely improve the overall sound. It may not, better doesn't necessarily mean that a better filter capacitor is needed mind you, but there should be no doubt that if better filtration does provide quieter DC, then it is entirely possible that it can also improve the sound. Again, you can reach a point of diminishing returns,where the DC may already be so quiet that any further improvements may not even be audible. One point though, in a direct coupled circuit has a cap shorting to ground, you'll have no output as it will go to ground via the "shorted" cap. I understand what you were trying to say, but a cap "shorted" to ground is effectively a wire.