Tube Life

Lewn, I aqree totally with you. I don't see any reason to leave tube gear on all the time. Most sound very good within a pretty short time after being turned on, while solid state gear can take hours to come up to full song.

Concerns about the thermal shock at turn on are over exaggerated. When cold, the filament will conduct more readily so that there is a quick in-rush of current and rapid heating at turn on. But, with tube filaments, this does not happen with the kind of speed and severity of something like a light bulb.

In any case, all my tube gear use tube rectification, so the signal tubes are protected from instant on conditions--it takes a while before the rectifier is putting out full current so it acts like a soft-start circuit.

Thorman's advice is good--with an extra "new" set, you can switch out tubes to determine if the sound has started to go bad. Weak tubes sound dead and lifeless compared to newer tubes. The only problem with this approach is that you have to pay for an extra set that you may never need.

There are some line and phonostages that run tubes so gently that they may not go bad in your lifetime. This would particularly be the case with the Telefunken 12AX7 and 12AT7 (reputation for long life). I have the other Telefunken 12AX7 equivalent (ECC803S) and I am hoping that that is the case (REALLY expensive variant).

On the other hand, there are designs that run tubes pretty hard. I recall that a dealer who kept Counterpoint linestages on for 12 hours a day had to change tubes every 6 months.