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Tube life span

Discussion in 'Amps and Cabs [BG]' started by jondog, Jul 30, 2002.

  1. jondog


    Mar 14, 2002
    NYC metro area
    How stupid am I?

    I left my '69 Sunn Sorado on in standby mode for at least 15 hours. Doh! It still works fine, but I'd like to know if leaving it on for extended periods significantly reduces tube life.

    Any thoughts from the tube amp gurus?
  2. Should not have been a problem... in my opinion it's harder on the tubes to cycle them on/off/on/off all the time.
    As far as the life span of the tube? That's a matter of how hard you drive them and how hard they get knocked around in transport. Generally speaking you should be able to get a couple of years out of MOST bass amp tubes. I know some people change them out every 6 months or once a year... but then again, some people change them every 10-15 years, or when they quit working.
    Don't sweat the load... at least it wasn't 15 days! :D
  3. JMX

    JMX Vorsprung durch Technik

    Sep 4, 2000
    Cologne, Germany
    Standby is there to prolong tube life.
    Leaving it on shouldn't be a problem.
  4. jondog


    Mar 14, 2002
    NYC metro area
    Cool, thanks.

    I don't have a spare set of tubes, and yes I've gigged it (I live on the edge). I did buy a nice case to protect it. Can anyone suggest a CHEAP source for tubes? This isn't my main amp anymore, but I'd still like to have replacements on hand. Used is fine w/ me.
  5. bben


    Feb 28, 2002
    Santa Fe, NM
    Rule-of-thumb for output tubes is 1500 to 3000 hours of use; standby doesn't count as use, tubes in standby are happy just sitting there humming to themselves. The physical shock of a complete warm-up / cool-down cycle is more stress.

    Preamp tubes can last practically forever, 10,000 hours or more in theory. In practice, there are a lot of ratty 12AX7s out there that give problems after a year or two.

    In my experience, cheap tubes can be more expensive than good ones in the long run, with more problems and the need for more frequent replacement.

    But anyway, my favorite tube source is Triode Electronics


    I have also had good luck with Antique Audio Supply


    Lord Valve knows his stuff, too

  6. Standby ain't all chocolate and cheese. It theoretically can lead to cathode poisoning by letting the cathode sit there hot, with no electrons being pulled off of it. A layer of material can form on the cathode that does not release electrons very easily, and the tube will not work right.

    All this is from old textbooks. I've never experienced it personally. Before I learned of it, I always put my amps on Standby for long periods of time. Now I turn them all the way off, or all the way on. No in between. I'll try and locate a link about cathode poisoning.

    My guess is that your tubes will pretty much be fine and dandy.

  7. Sufenta

    Sufenta Trudging The Happy Road of Destiny

    Mar 14, 2002
    The Signpost Up Ahead.
    How do you know that your pre-amp tube (12AX7 in my SM400s) is going bad? Every now and then when I really dig in or when I slap I can hear a static-like undertone coming through. Could this be my 6 year old, original 12AX7 giving up?
  8. jondog


    Mar 14, 2002
    NYC metro area
    Thanks for the links. Lord Valve has a pretty good FAQ.


    He says

    >As far as preamp tubes go, as long as they sound good and don't make any buzzing or humming/rattling/squealing noises, you can continue to use them. Of course, tubes wear out a little each time they're used, and it's difficult to tell from one day to another. I usually recommend that preamp tubes be changed every other time the power tubes are changed, as a general rule. Rectifier tubes can be used until they wear out completely!
  9. zombywoof5050


    Dec 20, 2001
    I've been using my Alembic F2-B for close to 20 years (thru both channels in stereo) and have never changed the tubes, and it still sounds great.

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