geoffkait....... " That’s a good point, but only in the sense that cable burn-in is fairly well agreed, you know, scientifically, that’s it’s actually the dielectric that’s changed by burn-in, not the wire. For fuses, who knows what burn in accomplishes? The solder joints? The air?"
Capacitors (and to a lesser extent tubes) are scientifically shown to need a burn in. You can hook them up to a tester and the differences after use are obvious. The cap manufacturers even state this and you can find it on their spec sheet. So I agree some components need burn in. 100%.
But scientifically I don’t buy the dielectric needs to burn in for a cable (a wire with insulation) and AFAIK no tester has ever shown a difference. Whether a person can hear something no machine made by man can detect is the debatable part. The dielectric in a cable is an insulator that can usually hold thousands of volts and I don’t see how a small voltage is going to change anything. But that is just me and I still had enough doubt to make a cooker and try it out (for free its worth it, I’m not paying $1000).
I made a burner for interconnects even though they carry an extremely low voltage/ current. I hooked up my speakers directly to the RCA output of a tuner and I had to put my ear to the speaker to hear anything. Even with line level CD output you had to be a foot or two away to hear anything. This got me wondering how this small amount of a current would ever effect a dielectric capable of taking 1000+ volts. But YMMV. Lets just leave it as there is no way I believe a phono cable needs burn in. They don’t carry enough power to even be audible directly connected to a speaker. How will that current ever change anything?
To further complicate things I also made my interconnects. I used small gauge wires (solid or stranded, pure copper or pure silver) and put them into an oversized Teflon tube. The wire is just randomly hitting parts of the Teflon and the the rest is just air. Like you mentioned how do you condition air? I am not sure this design even needs a burn in. But I did it anyway. If you believe the cable cooker spin I put at least 10,000x more voltage / current as you would get from line level in a couple of days listening to music (OK, I started drinking Scotch and the music got much louder than recommended at times). But now I know they are burnt in, no voices in my head giving me doubt and I can relax and compare my designs.