Tubes at idle

I don't think actual fire is a common event, but, then again how much is even a small risk? If replacement tubes are cheap, the only other major cost to consider is the amount of electricity the component burns at idle (some manufacturers give buys that figure). You have to decide for yourself whether the environmental issues matter to you. If the amp remains reasonably cool, then heat degradation of other components will not be that big an issue.

The only real advantage to keeping the preamp on all the time is the issue of warmup--that can be a big deal if you don't have time to wait or really dislike the sound of your system while it is warming up. I would at least listen to my system to decide whether warmup is that big a deal or not; I would not rely on consensus opinion on the internet.

For my own gear, I must turn it off to conserve the tubes because none of them are that cheap. My linestage runs four 310s and two 311s, plus a rectifier. My amp runs four 348s and four 349s (even more expensive than the linestage tubes). My phonostage runs two 300Bs as rectifiers, two tubes that I cannot recall the type (reasonably cheap) and two ECC803S tubes (quite expensive).

Koestner,

The risk of a fire from a blown or faulty tube is much lower with a tubed preamp than with a tubed power amp. However, that doesn't mean there is no risk, so it would be a good idea to turn the preamp off/unplug it from the wall ac if your going to be out of the house for several days and want to be extra cautious.

Tubes have been used in preamps since the beginning of home audio (supposedly, archaeologists have unearthed early examples in prehistoric caves in ancient Europe)and are still being used today, decades later. It seems a bit odd and disappointing that the issue, of whether it is best to turn tubed preamps off after each use or leave them heated and 'idling', has never been identified, tested and definitively resolved in all those years. Perhaps electricity and tube costs were so high that they never even considered leaving things powered.

Just some thoughts,
Tim

Here is the opinion of a High End retailer, "The Tweak Shop." It's only one opinion, take it for what it's worth.

http://www.tweakshop.com/Tube%20care.html

"Should I Leave My Tubed Component On All The Time?

"In 95% of the cases, no. There are a few components out there (like the T+A V-10 Integrated Amp) that have special circuits that provide a "trickle" voltage to the tubes, even when the component is turned "off". This does two things: It prevents the tubes from being "slammed" into operation when the unit is on, and it also means your "warmup time" to optimum listening is considerably reduced. Components like this are, therefore, "on" even when not "turned on", but this is a rarity. Energy-wise, a constant "trckle" voltage is not something we can recommend, as it can add up to a massive waste of resources. (Fortunately, that feature of the T+A V-10 can be switched in and out.)

"In an ideal world, we'd all use massive Vari-Acs to slowly bring our tube equipment up to operating voltage. But that's an impractical fantasy.

"It's something of a trade-off. Tubes don't like being turned on and off, but they also don't like being left on all the time just cooking. So it's sort of "six of one/ half dozen of the other". We think the tubes will last longer if *not* left on continuously, and many components feature a "soft-start" circuit that helps lessen the shock of turn-on.

"Bottom line: Unless you really do listen to your system 18 hours a day, turn off your tube gear and prolong the life of your tubes (and save big on your energy bill!)."

TOM AGAIN - And here is a link to a fairly lengthy discussion courtesy of someone who owns a recording studio, Sears Sound, on the topic of leaving equipment on or off. He does include vacuum tubes in his discussion.

He concludes that recording studio equipment should be turned off at night and acknowledges that others will disagree.

http://searsound.com/pdf/leaveiton.pdf

Again, it's not a scientific study, so take it for what it's worth and enjoy your music whether you leave your tubes on or turn them off!

Tom,

Thanks for interesting link to Sears Sound. I know that the primary concern in this discussion is the impact on the tubes, but, Sears Sound also mentioned the issue of heat impacting other components. That is also a concern that I have. Every manufacturer's specification sheet for parts, such as resistors and capacitors, includes an estimate of the lifespan of the component; this rating is not a single figure but one that relates lifespan to the operating temperature--the higher the temperature the shorter the working life of the component.

In an earlier post, I suggested that tube rectification provides a form of "soft start" for the rest of the downstream tubes. I should say that this is probably NOT as good at providing protection as a true soft start circuit. My linestage has an outboard power supply with a tube rectifier and an unbilical to the main unit. On turn on, even with tube rectification, there is a huge voltage spike (the main unit has a meter) and then voltage drops to the normal operating range. During this time, a circuit with a relay protects sensitive parts of the main unit.

One other word of caution. If you have to turn tube gear off and then plan to turn it back on again almost immediately, it is better to wait a few minutes rather than waiting only a few seconds. I have noticed that some gear will behave rather badly when turned back on quickly. This can take the form of making loud noises through the speaker and/or tubes emitting a bright flash of light (particularly the rectifier); I don't know how much harm this does, but, it cannot be good.

They do not, although their life shortens by idle hours as well.
It's definitely no go if you want to leave tube electronics on all the time especially when you leave your dwelling.
Tubes worm up substantially faster than semiconductors and therefore require only 5m of worm-up time before you start playing music. Than you need to idle them for another 5...10m of 'cool off' before turning off. Good quality 12AX7 pre tubes will serve you good decade with no problems.