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Tube Amp Shutdown

Discussion in 'Amps and Cabs [BG]' started by slap5string, Jun 26, 2012.

  1. What is the proper way of powering down a tube amp? For instance - a 73 SVT. Put into standby first? or just turn off? What is the potential harm of doing one or the other?
  2. From my understanding you should turn your amp on and leave it in stand by for a while to let the tubes warm up. Then turn them on. Shut down is different. Everything is already warm you are just killing the voltage to the tubes. Just turn everything off.
  3. ahc


    Jul 31, 2009
    No. Virginia
    No harm at all by putting it on standby first, then powering off. Plus, next time you turn it on, it'll be in standby for the warm up. This is the way I've always done it with tube heads. For a long time.
    Jim Carr and JMacBass65 like this.
  4. RoadRanger

    RoadRanger Supporting Member

    Feb 18, 2004
    NE CT
    While I agree with that I usually go on standby for a few seconds before killing the power just because I can :D . That and it assures that the mojo doesn't pool in the tubes and make a mess ;) .
    JMacBass65 likes this.
  5. BassmanPaul

    BassmanPaul Gold Supporting Member

    Aug 25, 2007
    Toronto Ontario Canada
    I've always just turned the mains off. With the standby switch in "operate" the residual conduction of the tubes drains the power supply quite effectively.
    Stumbo likes this.
  6. RoadRanger

    RoadRanger Supporting Member

    Feb 18, 2004
    NE CT
    Oh, I should have qualified that and said that's only an issue with inverted chassis amps ;) .
  7. BassmanPaul

    BassmanPaul Gold Supporting Member

    Aug 25, 2007
    Toronto Ontario Canada
    Right! On non inverted chassis like the Marshall line it's ojom! :D
  8. ...so putting the amp in standby before shutting it off "traps" residual power?
  9. nysbob


    Sep 14, 2003
    Cincinnati OH
  10. Stumbo

    Stumbo Wherever you go, there you are. Supporting Member Commercial User

    Feb 11, 2008
    Cali Intergalactic Mind Space - always on the edge
    Song Surgeon slow downer software- full 4 hour demo
  11. John D

    John D Guest

    Dec 27, 2009
    I played Fender Showman and Bassman 100 amps for years, and I always switched both the standby and power switches at the same time. The only exception was at break time, when I switched the amp into standby mode. The only failure I had in over twenty years of playing was once I switched my Showman on with the speakers disconnected. The output tubes were not happy. YMMV

    Edit: FWIW, some amps, such as my Ampeg SB-12 do not have a standby switch. I think this controversy started back in the tube radio days when applying B+ to a high power transmitter tube before it was warmed up could cause damage to the cathode. If I was playing a higher power amp, such as an SVT, I'd probably play it safe and warm the amp up before switching it off of standby, just to play it safe.
  12. ClaytonBassMan


    Jul 23, 2016
    If you put it in standby a few on shut down it cools the tubes some before shutoff and helps prevent a premature microphonic tube... imo
  13. Wasnex


    Dec 25, 2011

    I normally set my amps to standby for a few seconds and then turn the power off. My concern is the bias supply could collapse faster than the other power supply voltages. So the intent of leaving the power on is to keep the bias supply energized for a few seconds, after the rest of the circuit loses power. Perhaps I am being overly cautious.

    The standby on a 73 SVT interrupts the supply of voltage to the primary winding of the power transformer. So all power supply voltages are killed when you put the amp in standby, including the bias supply. The only voltage that is not effected by the standby switch is the heaters.

    Turning off the standby first probably still makes a bit of sense, because it significantly reduces the amount of current passing through the on/off switch. The on/off switch should not wear out as fast if you reduce the current load it is carrying before switching ;).

    I do believe the pop the amp makes is softer if you put the amp in standby for a few seconds, instead of switching the power off simultaneously.

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