Use pink noise disc to warm up stereo

Are you sure it’s not a matter of the equipment just being on vs playing the pink noise cd ?

While I can't speak to your stereo, my experience is that it just needs to be on to warm up. Pink noise, though, is allegedly good for breaking in signal cables, where a signal needs to be passing through the cables. 

I'd be interested if you notice a difference between warm up with no noise and warm up with pink noise..

Of course it depends on the equipment. Tubes definitely need to warm up. Most SS designs should not change audibly if they are well designed and working well.

Mine starts to sound ok-ish after 45min. but really starts to shine after around 2h. I have SS gear!
I guess it depends upon how transparent a system is and how experienced your ears are...