Tubes: On or OFF?

[microstrip]

Originally Posted by BillK

This is why I am wary of tubes anywhere but my phono stage, as the balance of my system is on 24x7x365.

Aside from power failures, I've turned my equipment off perhaps ten times over the past decade.

Can we assume you change the tubes of the phono stage every four years, perhaps on the 29th of February?

[DonBattles]

Originally Posted by Masterlu

If the tube gods wanted them on all the time we wouldn't have power switches.

This wasn't the way it always was. My MC240 didn't have a power switch and that's why I purchased my PS Audio AV3000. With the PS Audio I could leave the amp plugged in and manage a turn on sequence at the same time. As for the OP's question, I'm in the camp of not leaving them on

[Kingsrule]

The basic flaw in Skoff's argument for leaving your tube products on all the time is that he uses his experience learned at a radio station. A radio station is manned 24/7 so if a tube product goes up in flames there is someone there to deal with it. Many times home systems are left unoccupied and a flame up would be a disaster.
I do however believe that start up and shut down are the worst times for tubes and are the biggest factors regarding tube life.

[microstrip]

Originally Posted by g997

(...) I do however believe that start up and shut down are the worst times for tubes and are the biggest factors regarding tube life.

Yes, but not for thermal reasons. At start up tubes have no emission and usually the voltages in circuits are much higher than in normal operation. Also at power down, sometimes some tubes will reach dangerous voltages and currents, as some sections of the power supply will go down faster than others. Surely, a good designer will think about all these aspects - any old text on tube design refers to them.

Most of the time, when a tube breaks at power up or down, it is just because it was already partially defective or approaching the end of the useful life - the transients only fastened its failure.