Warm-up time for amps and preamps

There is absolutely no reason why running without input signal would be bad for any class D amp.  This strange advice was given by NuForce technician?  Are they still in business?

I believe the above rests on a misconception; it is advised by NuForce not to turn on their switching amps without speaker load - that is, with the speakers disconnected. I imagine that's what's referred to?

SS gear sounds best when the unit is left on. This is the truth to my ears based on my experience with numerous amps over numerous years. Class D amps most especially. 

Thank you, phusis!

rvpiano 

Half hour sounds about right to me. 

How long does it take for your system to sound good from a cold start?
I try to keep my system on most of the time. But occasionally I turn it off and it sounds like crap for a good half-hour to an hour.
i know there has been discussion here on the virtue of leaving tube preamps on all the time.
But my solid state amp (modified NuForce mono blocks) technician advises turning even them off occasionally.

Rvpiano,

I would say check with the equipment manufacturer/designer’s recommendation. If your ears tell you otherwise, then go with your ears. I leave my Naim equipment on 24/7 based on manufacturer’s recommendation. From my experience throughout the years, the Naim preamp takes 2 to 3 days to achieve optimal performance, the power amp takes several hours from cold. Most Naim users leave their equipment powered up 24/7.

As for my sources, I switch all of them off when I am done with the listening. The CD player has a standby switch and is warm to the touch when it’s on standby.