Basic tube amp question:

Discussion in 'Amp Tech Center' started by teleblastard6, Oct 21, 2019.

  1. teleblastard6

    teleblastard6 TDPRI Member

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    Need a straight answer to a 'dumb' question. All amps must be connected to a speaker, otherwise they're operating without a load. [ Damage will occur.] Does the tube amp also need connection to a guitar or instrument @ the same time to avoid said damage? Can I safely un-plug the guitar? Same rules for solid state & digital? Digital wireless devices? Need to get clear on this. Appreciate any help.
     
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  2. Dixon in Korea

    Dixon in Korea Tele-Meister

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    No, not having an instrument plugged in won’t hurt the amp. It’s still a good idea to plug the instrument in before you turn on the amp (or switch it from “warm up” mode to fully “on”) to avoid loud pops when you do plug in.
     
  3. simoncroft

    simoncroft Tele-Meister

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    ^^^^ Or turn the volume down before you unplug. :)
     
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  4. Dennyf

    Dennyf Tele-Afflicted

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    . . . Or unplug from the amp end instead if the guitar end. No pop.

    Btw, solid state amps are happy without a speaker plugged in (infinite load).

    Tube amps need a correct load to avoid harmful flyback voltages which are a consequence of having an output transformer.
     
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  5. teleblastard6

    teleblastard6 TDPRI Member

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    This is helpful, thanks, Dixon in Korea.
     
  6. teleblastard6

    teleblastard6 TDPRI Member

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    Good to know Simoncroft. Cheers
     
  7. teleblastard6

    teleblastard6 TDPRI Member

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    Solid State doesn't need a speaker plugged in when powered-up? Wow, I never would have thought that. But it does need the guitar plugged in? Thanks Dennyf.
     
  8. kbold

    kbold Tele-Holic Silver Supporter

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    ... or plug in.
     
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  9. Tonetele

    Tonetele Poster Extraordinaire

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    I was taught by a really old luthier 9 now passed) wrm up the amp if it's tube then plug in and allow plenty of time to coop ( 15 minutes) when gigging , then you can move it. Solid State is not a problem either way, although Roland Katana amps do have a standby switch. If an amp has a switch to warm up, better to do so.
     
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  10. Blrfl

    Blrfl Tele-Holic

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    Physics has a rule that says energy has to go somewhere. If you operate an output with a mismatched load (which includes no load, the worst mismatch of all), energy gets reflected backward and ends up back in the power section, either directly or through the output transformer if there is one. The worse the mismatch, the more energy is reflected.

    The reflected energy ends up headed for the components that do the amplifying (tubes, transistors), and those components have to absorb some or all of the energy. The energy they absorb are often turned into heat. If the mismatch and output level make enough heat and there isn't a heat sink or fan to get rid of it, the heat will eventually damage the components and they'll fail.

    Amplifiers don't put a signal on their inputs, so there's nothing to damage. Not having anything plugged into it is like being plugged in and not playing anything on your guitar or having the volume pot turned all the way down. The amp doesn't know or care; it just sees no signal.

    If you play an electric guitar unplugged (i.e., with no load on it), the output jack sees a bad mismatch and the energy created by the pickups is being reflected back. The amount of energy involved is so small that any heat it creates is too small to damage anything.

    Standby switches on tube amps shut off everything except the filaments so they don't have to be reheated when you turn it back on. Standby on a Katana just sets the output power to zero, effectively muting it. It doesn't have any effect on anything else in the amp.
     
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  11. rolandson

    rolandson Tele-Meister

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    There is no such thing. The only thing dumb about any question is not asking it.

    Yours, re: tube amps, is quite reasonable.
     
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  12. teleblastard6

    teleblastard6 TDPRI Member

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    Thanks, rolandson.. Although I was around during the classic rock era, & saw many of the great bands, I didn't play electric or own amps until around the time high gain amps began. Mesa Boogie, etc. Never played a Marshall stack, or maxed out a Bassman. So I started late & am a little out of sync.
     
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  13. teleblastard6

    teleblastard6 TDPRI Member

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  14. teleblastard6

    teleblastard6 TDPRI Member

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    Really informative Birfi. Thanks. & Thanks again to every one who replied to my questions.
     
  15. gusfinley

    gusfinley Tele-Holic

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    Most amplifiers have switched input jacks so that the input to amp is muted (shorted to ground) when a plug is not present. So, no, you don't need to have a guitar plugged into the amp.
     
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  16. Silverface

    Silverface Poster Extraordinaire Ad Free Member

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    NO!

    You misread the answer. NO amp needs an instrument plugged in. When we do tech work on them we rarely plug an instrument in ntil final testing, or bias adjustments, or when making tone tweaks.

    But there is no NEED to have anything plugged into the input in any type of amp.
     
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  17. POS Guitars

    POS Guitars Tele-Meister

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    All great answers. I will take it a step further. If your amp is not cranked super high and you're not currently playing through it, and you 'accidentally' unplug your cab, and plug it back in - nothing will happen to your amp. But don't do it on purpose.
     
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