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Leave it on or turn it off?

Discussion in 'Glowing Bottle Tube Amp Forum' started by Shoegrass, Jan 19, 2014.

  1. soulman969

    soulman969 Telefied Ad Free Member

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    As usual there's no real consensus of opinion here other than probably not leaving it on unless you nearby to attend to it if something bad does start to happen. If I'm playing on and off throughout the day mine tend to stay on. Both the tube and the SS amp. I may be putting a few hours on the tubes but surely no more than if I was gigging or recording that day.

    I've always tended to leave SS devices running since IME they tend to fail far more often when powered up than when left on. My stereo gear has stayed on like that for years with no problems at all. I'm not sure this is a right way or wrong way thing. It seems to me like more of a your way or my way kind of thing.
     
  2. CoolBlueGlow

    CoolBlueGlow Tele-Afflicted

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    Cathode poisoning

    The loss of transconductance (think "gain") in an amplifying tube, symptomatic of a loss of cathodic emission in oxide coated cathodes, and brought on by the operation of such cathodes for long periods of time without the presence of anode current. (e.g. Very long periods of time in standby with filaments hot and plates without B+)

    Thus the practice of allowing an amp to sit and cook in standby would appear to violate best practice for long cathode life.

    Cathode stripping

    Quoting RCA Transmitting Tubes vol 3, page 16

    "An oxide coated filament should be allowed to come up to normal operating temperature before voltage is applied to the plate. Otherwise a loss of filament emission may result"

    so, in typical SS rectified amplifiers, think "flip on both power and standby at the same time" Effectively, this provides instantaneous B+ on the plate with no filament emission. (Tube rectifier designs would not suffer this except on the rectifier itself!)

    Thus, the practice of not using the standby switch during power up would appear to violate RCA's recommendation, above.

    Note: all tubes currently popular in valve guitar amplifiers commonly discussed on this forum contain oxide coated filaments of one type or another.

    I'm just using RCA recommendations. If they are wrong, I am wrong.
     
  3. waparker4

    waparker4 Doctor of Teleocity Ad Free Member

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    ^ what he said
     
  4. Rich_S

    Rich_S Friend of Leo's Gold Supporter

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    No, NOT using the standby causes cathode poisoning. Cathode poisoning occurs when high B+ voltage is applied before the filaments are heated up. The case that causes this the worse is amps with solid state rectifiers and no standby switch. Turning on the power applies B+ immediately because the SS diodes don't need to warm up. So, these amps need to have the standby switch that turns the B+ off, giving the audio tubes time to warm up before B+ is switched on.

    Tube-rectified amps are a little easier, because the recto has to warm up, too, and B+ comes up more slowly. Still, it's better to warm up the amp in standby before switching to "play".

    I don't have much to add to the OP's question. My rough breakpoint is about half an hour. If the amp's going to sit less than that, leave it on. Any longer, turn it off.
     
  5. waparker4

    waparker4 Doctor of Teleocity Ad Free Member

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    Read what CBG wrote

    Here's another link
    http://www.valvewizard.co.uk/standby.html
     
  6. Jack S

    Jack S Friend of Leo's

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  7. Shiro

    Shiro Tele-Meister

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    What I don't understand is if the standby switch is so evil, why do most of the major manufactures including boutique builders put the darn thing on there in the first place?
     
  8. waparker4

    waparker4 Doctor of Teleocity Ad Free Member

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    1. It's good for warming up the tubes for 15 seconds before playing
    2. Famous amps in the past had the standby switch, therefore, since guitarists are technologically conservative, amps must continue to feature the standby switch.
     
  9. surfoverb

    surfoverb Doctor of Teleocity

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    its not evil when used properly. It does reduce wear on the tubes if using an instant power rectifier like a 5Y3 which is really common on tweed deluxes.

    but then vintage 5E3s didnt have one

    my clone does though

    basically when you turn on a 5E3, the 5y3 tube generates full power almost instantly, but the other tubes (6V6, 12ax's) need time to heat up before recieving all that power.

    Thats how I read it anyway, tubes are freaking rocket science almost and not easy to understand so I take experts words on it. but i dont think it makes that much difference. in my experience Power tubes wear out from play no matter what you do. especially on Marshal amps for some reason they go through power tubes once a year if you play a lot.
     
  10. viking

    viking Friend of Leo's

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    Power consumption cost a lot of money here where I live , so everything that isnt used get switched off- guitar related or not.
    If any of my amps cant tolerate this over time , they will get fixed.
    On the amps that I have with a standby switch , I dont even care to use it , I just turn the amp off and on. Also , at gigs I turn it off between sets , why not ?
    I have been playing for several decades and have never had any problems.....
     
  11. CoolBlueGlow

    CoolBlueGlow Tele-Afflicted

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    I humbly concur with Mr. Peavey's explanation, previously posted. In particular, Mr. Peavey's inclusion of current inrush limiters in their tube plate supplies is thoughtful and would seem to be a wise decision for tube reliability.

    In addition, see ValveWizard's explanation of standby switch design flaws and philosophies, here.

    http://www.valvewizard.co.uk/standby.html

    I also humbly concur with the Wizard's analysis of the shortcomings of most current standby switch designs. (e.g. classic Fender/Marshall etc. HT cutoff switch)

    There are some great tips in Wizard's writing (link, above) on simple improvements in standby switch designs, and on extending the life of your cathodes by reasonable design and operational practices.

    Wizard doesn't mention the danger to cathodes via instantaneous inrush current in SS rectifier designs. As I previously annotated, RCA technical literature makes it abundantly clear that this is not a good practice, (as does GE literature).
     
  12. mherrcat

    mherrcat Tele-Holic

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    That Peavey article really helped me understand cathode stripping/poisoning. Copied it to the desktop on my computer for reference...
     
  13. CoolBlueGlow

    CoolBlueGlow Tele-Afflicted

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    Yes, a nice piece. I also enjoyed reading it too.
     
  14. guitarsrmine

    guitarsrmine TDPRI Member

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    In my band, at every gig when we go on break, I say to my son, "Save those tubes!!"......our amps get turned off
     
  15. Old Bill

    Old Bill Tele-Holic

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    Scientists working for the British government during the war discovered that the reason their computer(the one at Bletchley which decoded Enigma messages) kept blowing valves(tubes) was because they kept switching it on and off, so they left it on all the time.:confused:
     
  16. KevinB

    KevinB Doctor of Teleocity

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    I leave my main SS amp and modeller on 24x7. The tube amps get switched on and off as I use them. In their case I think heat causes more problems than the surge from the act of powering up.
     
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