Burn in vs perception

Okay, well, I am experiencing burn in / settling in a speaker cable. Cardas Cygnus long run, 6m. Replaced Wireworld Equinox. Mc to SF speakers.
 

When I first installed the cable, I was so excited to hear my improved system. It sounded awful (closed, dull, grainy treble), and I wanted to send the cables back, but that wasn’t even an option because they were a custom length. I was assured by Cardas to give it time 200-300 hours. I was skeptical. 
 

Well, I’m probably at 100-150 hrs now, and the system is sounding pretty extraordinary (great sound stage, smooth treble, dynamic). So have I just gotten used to the change—perhaps, but I’m pretty sensitive to any change in my system, and it sounds very good now. And getting noticeably better each day. I’ve read that cables need a settling period to charge the dialects surrounding the copper, so maybe there is a real reason for this, or maybe it is my changed perspective, but I don’t thinks so. Perhaps, with this cable settling in, I’m for the first time understanding what good PRaT is. 

"We're excited about our burn-in process. Since adding it as part of the manufacturing process, our 60-day satisfaction guarantee refunds have gone from roughly 6% to less than 2%. The comments from customers went from, “They're good, but a bit restricted sounding,” to, “Man, these things rock!”

No, we’re not kidding, the difference is night and day. That’s how we hear it, and that’s what end users are telling from all over the world."

Zu Audio On Their Burn-In Process

Capacitor Burn-In

"This description may be leading many to wonder if they’ve been buying scrap? But the picture isn’t that bad. The capacitors are generally OK from a correct (or near correct) value point of view. It’s just that the quality of dielectric is wanting at switch on. The quality of dielectric affects the leakage performance, and although the circuit will function correctly, by which I mean it will establish the correct voltages, the sound quality at switch on clearly isn't that which the product gives after a number of weeks use.

Therefore a piece of high performance hand built equipment simply will not sound as intended at first. It may not sound as intended for a number of weeks. The sound can go through changes as one capacitor comes on-stream while the others are still getting there

I am still in the honeymoon stage with a new 300B amp. As of now I have about 40 hours on it. Last night I could clearly hear that something was different. The dynamics just opened up in a big way. The sound out of the box was very good, but maybe a little tight. Last night the swing factor was on full display, just sounded like a more powerful amp in every way.

@ozzy62 - in your case, I'd say both the amp's electronics and the tubes need breaking in; in my experience, tubes mostly sound at their best after at least 100 hours. You've probably got a good bit of improvement left to look forward to....