paullkSo just hypotheticaly wouldn't say swaping the fuses with solid copper bypasses net you the best sound? Assuming there is a large gain here, you could then swap different fuses in and out to see which ones affect the sound the least.
YOU Can't Handle the Truth! ...okay, you probably can, but let's start with background.
Most audiophile equipment uses linear power supplies. Not all, but most. Let's stick to power amps though ... and most use linear supplies.
In a linear power supply, there is only conduction between the AC line and the storage capacitors of the supply for a relatively small portion of the AC waveform. In North America, at 120 times/second, the AC line is contributing power to the capacitors for somewhere between say 0 - 2.5msecs out of 16.6msecs. 0 when the volume is low, 2.5 when it is high. The 2.5 is variable based around static load of the amplifier, post regulation, amplifier feedback to reject power supply noise, etc. It could be more, but in high quality amps with enormous capacitor banks, it is often quite small.
So now let's throw in the concept of power supply rejection ratio. This is how much of the ripple on the AC power supply ends up in audio output going to the speakers. It varies a lot from amp to amp, but in general, it is highest at low frequencies and lowest at high frequencies. What that means is the amplifier is usually pretty tolerant to "noise/ripple" in the power supply at base frequencies, but sensitive at high frequencies. So, 1 or 2 volts or ripple at 120Hz on the power supply caps may be totally inaudible, but if you had 1-2 volts at 2KHz, their would be an audible buzz.
The power supply for the high power rails is often quite simple ... a fuse, some EMI caps/inductors, and a big transformer followed by diodes and those caps. Those diodes turn on/off really quick, and that causes high frequency noise. The noise a factor of current and how fast the current transitions from on to off, which is a factor of how fast the voltage transitions across that diode, which is a factor of the bandwidth of the circuit comprising those capacitors, transformer, EMI components, and fuse.
What reduces bandwidth? ... Resistance. Resistance can reduce the noise of the diode transitions which reduces the high frequency noise where the audio circuit is most susceptible.
Nothing is ever this simple, but the simple answer is no, a wire is not always better and in many cases may be worse, especially in lower power equipment. That resistance not only reduces noise in the component, but also reduces noise from the component getting out onto the AC line.
