Debate: Class D amps need 48 hours of warmup

In short, the amount of time is not important.  At the component level, especially IC's, there are behavioral differences caused by temperature.  If you experienced a difference after a 48-hour warmup, it was simply due to the difference in temperature between the two times you listened, your blood pressure, mood, what-have-you. 

I turn my Hypex powered Marantz integrated off overnight during unsettled weather. About 20 minutes after turn-on, it’s back to peak.

When I had an all-tube Cary SLI-80, it would take 45 minutes to an hour to sound its best.

Then there was the class A Pass Aleph. If it was shut off for more than a couple of hours, it wouldn’t sound its best til the next day!

If class D amp changes (improves) sound after few hours, I would recommend to see a “hi-fi doctor” :-). 

Despite class D amps are running much cooler comparing to AB/A amps, stress conditions on internal connections/soldering/capacitors/etc are much higher than hot A or AB class amps. I’ve seen capacitors “resurrect” after running few hours, closer to 50%/75% normal, despite 30% performance at start! 

The HIFI Rose RA280 sound pretty good after the third songs out of the box. It plays many times for the last few months. It is getting less digital like and more tube like compares to my Muzishare RA100+X9 combo. Each time only take a few songs to make me forgot it is solid state amp, just a very good integrated amp. 

Mine power up instantly. They do not run warm so waiting for warm up is not logical.