Those black boxes degrade sound?

Those "black" boxes on cables are usually low pass filters, cut off above 20KHz. They probably do not degrade the sound, if you only listen to CD playback, and not analog MC cartridges. But are they needed? I do not think so!

MIT and Transparent cables "boxes" contain passive componentry which linearises transit time, such that all frequencies are theoretically in phase at the load end of the cable. Far from degrading your sound the networks are installed to enhance the listening experience --- eh? No they do not wear out, although they can be damaged via inappropriate usage or application of breakin boxes incorporating excess voltages or a DC component.
These networks are not just there for decorative purposes, and if they were't needed, they wouldn't even be there now would they? (indeed an absurdly speculative statement from the uninformed).

VooDoo "Fixing" the phase after the fact? and exactly how do these boxes decide how much out the phase was. or is? out of wack.
I'll keep it as is. I have not heard the current crop of these things, but did hear another one no longer manufactured, and it was not very helpful.
IE: the sound was btter without the boxes, all else being equal. Now that was to my ears... some folks liked the smeared sound.