Tube preamp, Leave On Always or ON/OFF?

I substantially agree with Jfrech. Mine is a tradeoff. I use a very difficult to obtain tube with a 10,000 hours usable life. This is about a year and a half when always on. It takes my preamp about 2 hours to reach its peak, and I typically use it for 3 hours each night and about 5 hours each weekend. Thus I use about 41 hours per week turning it on and off, rather than 168 hours leaving it on. My tubes thus will last about 5 years.

If you have the dough to replace tubes often, then leave it ON; otherwise leave it OFF when not in use.

ALWAYS ON. Solid state or tube. Always.

I never turn mine off. It's an Audible Illusions M3A. It's known as a "tube eater". I had the same tubes in it (Amperex JAN) for 5 years. The JAN's are still good! I just took them out to listen to different tubes.

Think about it. Professional studios leave everything on constantly. Nothing heats up then cools down then heats up .... These expansions (heat) and contractions (cool) cause a shorter life.

To test this, leave a light bulb on. Isolate it from all vibrations. (You never thought you'd be using cones, cork, sorbothane, ... for that, did you?) That light bulb will last longer than any other light bulb from the same pack.

I used to leave them on all the time. Now I turn them off as I got tired of replacing them often.

I have a BAT VK-50SE and I like to turn it off when not in use.

The BAT has a soft start feature, which gradually increases the voltage to the tubes over a period of time (about a minute). It drastically reduces the stress on the tubes during power on. Turning this kind of equipment on and off should not shorten the tubes life.

The BAT runs very hot. The heat it generates may shorten the life span of other components inside. Leaving it on all the time is going to dry up the capacitors sooner.

Not to mention the extra electricity it consumes.

But if you have a preamp that has no soft start feature, drives tubes gently, does not run very hot, and uses long lasting tubes; than by all means, leave it on.