Changing an amp's ohm setting while in standby?

Discussion in 'Amps and Cabs' started by scriptphase, Feb 19, 2012.

  1. scriptphase

    scriptphase Member

    Messages:
    770
    Joined:
    Apr 5, 2007
    Location:
    Alamogordo, New Mexico
    Probably a silly question, but is it okay to do this? I figure it is, but I've been playing it safe and powering down first. I'm taking one head and switching between 16 ohm and 8 ohm 4x12 cabs. No load is necessary in standby, so this is okay?

    I know there's no problem switching two heads between one cab as long as they're on standby, so I imagine this is no different?
     
  2. StompBoxBlues

    StompBoxBlues Member

    Messages:
    18,618
    Joined:
    Sep 20, 2005
    Location:
    under the stars
    I don't think it is a problem either, but I DO always tend to play a chord or something after I switch to standby, to hear that chord die out when the signal is totally bled...

    THEN can switch over.
     
  3. galibier_un

    galibier_un Supporting Member

    Messages:
    767
    Joined:
    Sep 25, 2006
    Location:
    Colorado
    On a related topic, tube amplifiers like to see a load (a speaker) when running (not on standby).

    If left running (not on standby) for a long time without a load/speaker you can hurt your amp. When you're on standby, you've disconnected the high voltage supply to the power supply circuit, and therefore to the tubes. As StombBoxBlues mentions, it takes some time for the sound to die out - the time it takes for the power supply capacitors to discharge.

    Leaving a speaker disconnected from the output of the amp for 10-15 seconds won't blow anything up, but it's good practice to not do this, if only because you might get into a bad habit.

    Cheers,
    Thom
     
  4. Structo

    Structo Member

    Messages:
    9,573
    Joined:
    Apr 10, 2007
    Location:
    Oregon
    Why would you want to do this?
    You aren't going to switch impedance during a gig are you?

    To be safe turn on standby, play a chord to drain the caps then turn the power off.
    Switch impedance and power back up.
     
  5. Billion81

    Billion81 It'd be a whole lot cooler if you did. Gold Supporting Member

    Messages:
    2,897
    Joined:
    Sep 26, 2009
    Location:
    in a hubzone
    I get it. I will have different cabs ready to plug in when checking head/cab combos- Still, best practices and all that.

    I have thought of this question as well- What (I think) he's getting at is:

    Does the power section (OT/PT/Rec) need to adjust based on the tap selected out to the speakers and would a complete power down be safer than switching the tap or impedance while on- even in standby mode ??

    Said another way- are you changing anything from the rectifier or other element in the power section when switching the taps?
     
  6. blackba

    blackba Supporting Member

    Messages:
    9,315
    Joined:
    Dec 10, 2005
    Location:
    Michigan, USA
    I have done this many times without issue. When I am testing cabs is when I switch impedances and cabs when the amp was on standby.
     
  7. scriptphase

    scriptphase Member

    Messages:
    770
    Joined:
    Apr 5, 2007
    Location:
    Alamogordo, New Mexico
    Thanks to everyone that responded for the info. My understanding of how impedance switches work is that they activate different amount of windings in the PT. Didn't know whether that was safe to switch around while the amp was powered on...even in standby. Sounds like I'm being overly cautious as I'm putting the amp in standby, powering down, switching the impedence setting on the amp, then powering back up. All this over the span of several minutes. :bonk

    No, not during a gig. I agree...that would be weird. I've ended up with three 4x12s (a 8 ohm and two 16 ohm) and I'm trying to narrow it down to one keeper if I can due to the sheer space these cabs take up. I hear differences between them, but it's hard to nail it down completely without making immediate comparisons like I would with pedals, guitars, or (even) heads on standby that I can switch between quickly. What I really need is a proper recording setup. Maybe I'm over-thinking things, but I'm also wondering if I like the sound of the AMP in one impedance over the other. Is that even possible? The PT (and its impedance) isn't really part of the tonal chain, is it?
     

Share This Page