Can you leave class D amps on and not ever turn them off?

Grannyring, give it a try. Afterwards of course you will still have to wait for it to reach its optimum operating temperature for best sound but it will provide better overall sonics for a while. Let us know later if this made a difference.

George,

You mention NuForce 8 monoblocks as having gone up in smoke.
Would you suspect the Nuforce 9's as having  the same problem?

rvpiano OP
George,
You mention NuForce 8 monoblocks as having gone up in smoke.
Would you suspect the Nuforce 9's as having  the same problem?

Many use the same generic SMP boards from the same manufacturer just different rail volts, so it wouldn't surprise me if they were similar.
See this post of a Nuforce 9se v3 I posted in Stereophile and what it did to a reviewers pair of Wilson Watt Puppy 8's, this wasn't a powersupply issue just the nasty noises the 9se made.
http://www.stereophile.com/comment/561214#comment-561214

Cheers George

Thank you for your reply, George.
I own the original Nuforce 9's and have kept switching them on and off for years.
i guess I'll continue to do so, even though, for a brief period, I left them on and didn't have the annoyance of waiting for them to warm up.

Oh well.....

**Usually** keeping filter caps charged is a good thing for their lifespan. If however that means that the caps also are running warm then its not going to help, especially if some of that warmth comes from ripple current (which tends to be higher at higher frequencies as seen in SMPSs). Careful circuit design can avoid these problems.

As one who has spent a lot of time studying the idea of going off grid and using solar power and the like, one thing that comes up in sorting out how much power you're going to need is how long something is on, and not so much how much power it draws. Class D amps are typically around 85% efficient so a 500 watt amp is going to draw some power even if its just sitting there at idle. Since there is never dead silence even when the preamp is off, that means the output section is engaged even if its not making a lot of power reproducing background noise.

I get that some solid state circuits sound better after they are on for about a day or so. IMO this really says that maybe they aren't all that green compared to tubes if you tend to leave them on all the time so they will sound right.