Break-in of a Class D amp?


I'll spare everyone the "brand tribe" debate, and keep my question/details generic.

I recently had to have my 2ch ClassD amp "serviced" by the manufacturer.  Yes, it's an ICEPower derived unit.  I'd been SUPER happy with it for well over 18 months, until one morning when I heard a buzzing coming from inside the amp itself.  I took a video, poked the manufacturer, and they voluntarily opted to fix it for me.

Fast forward a week, and the amp is back in my stack.  But something is amiss. 

I can tell they wholesale replaced the entire ICE module, as the "power up" delay from standby is "different" than before, and it seems to exhibit less overall "gain" than prior to repair.

But the most disturbing thing, and one that literally smacked me in the face... was the lack of high frequency authority.  While there is a soundstage, and lows are not an issue... it's missing all the "presence" and "life" in the top end.  I have tracks that I can play that elicit EMOTION when I queue them.  All the detail and fidelity is like, muted.

The previous board had hundreds of hours of time to burn in, and boy I exercised it.  Is this what I'm now encountering?  Or has anyone out there experienced this situation?  

I would normally just knuckle down and "grind out" hours of "work" for the amp... and not come here asking for advice... but the fidelity difference is so striking... that I can't get over it.

Thoughts?
rabbottmke
PS Audio had a video recently commenting about burn in time. The number of amps returned to them significantly dropped when the burn in time was increased. Maybe give it some time? 
I recently bought a Class D (Pascal) stereo amp and the owner for the company told me he did not think the amp needed any burn-in. I think he may have been correct since I have not notice a change in the sound (brand new build). My Benchmark AHB2 amp did not need any burn-in either. 

All other gear I have owned sounded considerably better with burn-in.
Sounds like they fixed a problem with a hyped top end to me. In any case I have never heard any component go from rolled off to extended during burn-in. Always the other way around as the high frequency grain and etch that masquerades as detail becomes more liquid natural with time.
Thanks for the feedback, everyone (pun intended).

I guess I'll keep at my burn-in over the next week or so, and if it's not improved... it goes back in the box, and into storage or something.

I've always lusted after blue VU meters.  Maybe it's time to chase some down.