How long to leave an amp on standby?

Discussion in 'Amps/Cabs Tech Corner: Amplifier, Cab & Speakers' started by Figaro, Feb 16, 2012.

  1. Figaro

    Figaro Supporting Member

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    I've read (can't remember where) that you should not leave an amp on standby for too long, like between sets, etc... which I think most players do. I think it said it's better to just leave it in play mode. Can someone explain why?
     
  2. wall_of_sleep

    wall_of_sleep Member

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    Cathode stripping. Some believe this will shorten tube life and some point out that this will only happen with high voltage transmitter tubes. There are a number of threads on here that explain why the majority of guitar amps do not require standby switches.
     
  3. Zerksies

    Zerksies Member

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    There shouldn't be a problem in standby it is only keeping the filaments warm
     
  4. Strat

    Strat Member

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    Mine has been on for about a year in my practice room.
     
  5. dallasblues

    dallasblues Member

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    My '51 Pro (my main amp) doesn't have a standby switch. I don't miss it.
     
  6. GearHeadFred

    GearHeadFred Member

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    But the filament is heating the cathode, so it's emitting electrons.. and they have nowhere to go :sarcasm

    There are many threads and opinions on this so I'll just post my opinion. It's perfectly fine to leave a guitar amp in standby for 20 minute breaks.

    I would avoid VERY LONG periods of standby.. like multiple hours.. if possible.. but it's debatable whether that will cause any problems as well.
     
  7. donnyjaguar

    donnyjaguar Member

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    I left my Fender Concert II on for two weeks once with no ill-effect. Most filaments blow during power-on anyway in my experience.
     
  8. wyatt

    wyatt Member

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    The myth is that it will "poison" the cathodes, which doesn't happen in common audio tubes (well, unless you;re using NOS from the '40's or something). People often forget and leave their amps in standby for days and then find a tube is dead when they return...it's dead because it wore out and would have died anyway.

    There certainly is no danger in leaving your amp in standby for a 45-minute break...that's why Leo Fender put the switches on to begin with.
     
  9. CA_Dan

    CA_Dan Member

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    I don't leave them on standby for too long because of the PT. I've read different opinions on this, but some transformers are not designed for continuous use. If the heaters run off a secondary of the PT, I would think leaving the amp on for a long period of time could damage the tranny. Probably an over abundance of caution on my part. Anyone know for sure about this?
     
  10. dallasblues

    dallasblues Member

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    Since my old Pro doesn't have a standby, I either turn the volume completely down or simply turn the amp off between sets. I haven't seen any ill effects of doing either.
     
  11. Timbre Wolf

    Timbre Wolf GoldMember Supporter Gold Supporting Member

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    Don't worry about leaving the amp on standby for too long.

    Cathode stripping can occur when B+ is applied before the filament has come to sufficient temperature. Leaving the amp on standby keeps the filament powered, but removes the B+... you can go on like that for weeks.

    - Thom
     
  12. Figaro

    Figaro Supporting Member

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  13. Timbre Wolf

    Timbre Wolf GoldMember Supporter Gold Supporting Member

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    I was speaking from personal experience. I've left an amp on standby for nearly 2 weeks, with no ill effects. But I don't routinely do that. My point: it is nothing to get worked up about. Best to spend your time fretting your guitar, and not fretting these small points.

    Thanks for the article, Figaro - it has some good points. The slow-warmup (indirectly heated) vs. quick-warmup (directly heated) rectifier details are important to pay attention to.

    - T
     
  14. midnightlaundry

    midnightlaundry Member

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    The Wizard said CP only happens with uber high voltages like in transmitter tubes.
     
  15. wyatt

    wyatt Member

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    That's cathode stripping.

    Cathode poisoning happens in many tubes, but I believe it is material dependent.
     
  16. midnightlaundry

    midnightlaundry Member

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    You're right. I double checked the book. He said CP could happen by leaving heated cahodes with no B+ for several hours; which is a bit vague. But he foot notes the Radio Designers Handbook 4th edition, 1957. You're probably good for at least an hour, which would never happen at a gig.

    This was from his section on standby switches, where he kinda bags on them. I still think a standby is useful for finding shorted power tubes without going thru a box of fuses. Furthermore, tube structures will still expand and ping inside the glass long after the heaters come on. I like to wait a bit before I go full retard.

    I once left an amp on standby for about 24 hours! It didn't blow at least. I couldn't tell if the tube lost any fidelity.
     
  17. ScottR

    ScottR Silver Supporting Member

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    I left my Budda SD45 on for 8 days...no harm done
     

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