Should preamp be left turned on?

I'd leave it on unless there was a danger of electrical storms, in which case I'd switch it off and unplug it. Otherwise I see only benefits in leaving it on ... longevity, sound (maybe), and no downsides (unless it's got a huge power consumption, which is very unlikely).
I leave my integrated amp on all the time, but I turn the volume to minimum and select an unused input when it is not in use.

Yes. I have the same.

I've been leaving ss electronics continuously powered up for 35 years through three systems and have yet to need a repair.

I second SeanDTaylor: Longevity is a benefit only for low power - which a preamp is. For high power Class A or tube amps, this point would be ambiguous (Pass X600 springs to mind). I leave mine on all day and off only at night as, what I feel, is a balance between thermal loading and thermal cycling. Arthur

I've heard it said that SS should be left on and tube should be switched off.
The reasoning was that SS takes a long time to warm up, and that thermal cycling causes expansion and contraction that can break components (e.g. causing electrolytic caps to break and leak).
Tubes, on the other hand, wear out the heater element if left on all the time, and warm up very quickly when switched on.
I have only ever owned SS and never class A so the electricity bills have never been a problem.
I suppose a fireman, sorry, firefighter, would tell you that all electrical equipment should always be switched off and unplugged when not in use. I wonder what an audiophile firefighter would say? :-)

Leave it on. Power down and unplug only during electrical storms.

I leave my Spectral DMC-30S powered up all the time. I don't really have to worry much about electrical storms here in San Diego.

How do you like your DMC-30SL?

From a recommendation right here in the forum, I just purchased a Pass Aleph P preamp from a fellow Agoner. It does not even have a power switch! It is an excellent piece.

I think they put the power switch on the back for a reason. I would take that as a manufacturers recommendation.

My pre doe not even have an on/off switch. Heh heh heh...
Ayre K-3x

KF

All Pre amps leave on! Even Tubes.

Seandtaylor's first post hit things right on the head. Sean
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Agree with majority, for solid state pre-amp leave on 24/7 unless bad storm coming then power off & unplug entire system. Most SS pre-amps consume under 20 watts so cost of power is not an issue.

I might add my advice is for system with some sort of surge protection in place 24/7

I had to respond to this one! Seandtaylor99, I'm an audiophile firefighter, and I leave my stuff on:)

Vern

Thanks Vern ... and good job !