Help me not destroy my GK amp

Discussion in 'Amps [BG]' started by garytw, Dec 6, 2013.


  1. garytw

    garytw

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    Hi bass friends. I have a GK MB150 and a GK 200MB. Both are nearly identical combo amps. I would like to use the 150 as an extension cabinet for the 200. My question is: Can I plug a speaker cable from the 200 into the speaker OUTPUT of the 150 without damaging the circuitry of the 150? By doing that, the 200's speaker output would be sent directly to the 150's speaker. The 150 would of course be off and unplugged from AC. I don't want to modify the 150 by adding a speaker jack so I'm wondering if my bizarre plan will work?
     
  2. bassteban

    bassteban

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    That sounds wrong to me
     
  3. BurningSkies

    BurningSkies Supporting Member

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    I'm not quite sure what you're describing. Does the speaker for the 150 have a separate cable that dis-attaches from it's amp? That's the only way that you wouldn't make things go south fast.

    If you're talking about running a line from the 200's speaker out into the 150's speaker out, you're in for some fireworks.
     
  4. guroove

    guroove

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    Don't do it. The 'speaker out' is connected to the power amp, not the speaker. This won't work. Get an extension cabinet, or rewire your 150 so that it becomes an extension cab. What you're describing won't work without modifying the amp.
     
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  6. Joe Louvar

    Joe Louvar

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    No.

    If you want to drive both combo amps simultaneously I recommend using either the Lehle splitter or Radial BigShot switcher - I have the Lehle.

    Lehle Splitter
    http://www.musiciansfriend.com/amplifiers-effects/lehle-p-split-splitter-guitar-pedal

    Radial BigShot Switcher
    http://www.musiciansfriend.com/ampl...neering-tonebone-bigshot-aby-passive-switcher
     
  7. Joe Louvar

    Joe Louvar

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    This is what the OP is talking about.

    +1. OP: Don't do it.
     
  8. garytw

    garytw

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    Thanks everybody. I think the consensus is... DON'T DO IT! I forgot to mention though that the internal speaker on the 150 is wired to the circuit board at the same point that the external speaker jack is. My plan was to backfeed through the external jack to the internal speaker. I know it works after doing some (safe) testing with a meter. And remember, the 150 will be a brick, totally off and unplugged from power. So I doubt there would be fireworks, but would the voltage from the 200 output harmlessly pass to the 150 speaker or might it have some affect on the output circuitry of the 150, which is totally without power?
     
  9. BurningSkies

    BurningSkies Supporting Member

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    The problem is that you're applying voltage to the output of the 150's amp, on or off, you don't want to do that.
     
  10. garytw

    garytw

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    I think I'll take everyones advice and add a jack that will disconnect the amp. Thanks again.
     
  11. nysbob

    nysbob

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    Why do that when you can easily go into the front end of both of them? If you want an extension cab, buy one. I think what you are proposing is a recipe for trouble.
     
  12. sotua

    sotua

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    Maybe what you could do, if there are FX loops in both amps, is take a FX out from your main amp and feed it into the FX return of the second amp. You'll have to plug both in, but that way you could have the same signal in both power sections.
     
  13. singlemalt

    singlemalt Supporting Member

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    Why not spend half an hour putting in an input jack?

    I see your point about how it is wired, and I get what you are saying, but you are about to bet your amp on your theory.

    Good observation is key to experiments like this. Can you video tape the trial from a safe distance?
     
  14. Joe Louvar

    Joe Louvar

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    Okay.

    Yep, don't do it. You're welcome.

    Quit trying to cheap out and just do it right - if you want to drive both combo amps simultaneously use something like either the Lehle splitter or Radial BigShot switcher - I have the Lehle.

    Lehle Splitter
    http://www.musiciansfriend.com/ampli...r-guitar-pedal

    Radial BigShot Switcher
    http://www.musiciansfriend.com/ampli...ssive-switcher

    TIP: note - ISO output, ground lift, and phase switch on above devices - also when you use one of the above devices, make sure you plug both amps into the same AC outlet.
     
  15. B-string

    B-string Supporting Member

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    Last time I know of personally a borrowed Line 6 modeling amp was plugged into the extension speaker jack of a 212 combo. Guy said it sounded pretty good for about maybe 2 minutes then the smoke poured out of the Line 6 amp and the combo blew a fuse when he tried to use that instead. He couldn't do the gig and brought both to me for repair.

    Just because the amp may be off does not mean it is "out of the circuit". In short, don't do it.
     
  16. DrDAV14

    DrDAV14 Supporting Member

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    Just buy the 112MBX and know your doing the right thing. I have one I'll sell you if you need.
     
  17. jeff7bass

    jeff7bass

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    Get an A/B box, a chorus with two outputs or a Sansamp Bassriver, which also has two outputs. Now you can run both combos in stereo and better yet, you can EQ them both independently.
    With the Sansamp, you can send an overdrived signal to one and leave the other one clean and fat. Good chorus pedals, like the TCE bass chorus, have two outputs for that big "lush" effect that fills the room. Jeff Berlin runs one into his two Markbass Jeff Berlin combos! An A/B box just splits the signal into two with no effects.
     
  18. jehhorton

    jehhorton

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    +1 on the a/b box. I use two amps in my guitar rig with an a/b box. Much less trouble, and fairly inexpensive.
     
  19. stratovani

    stratovani

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    I play through two GK MB115 combos, and here's how I wire it up. First off, I made myself a custom instrument cable, 4ft long, with a right-angle plug at each end. Next, I plugged one end in the active input of one combo, and the other end into the passive input of the other combo. I then max both master volumes, and control the amp volume with the Gain knob. Works great for me, it's insanely loud with lots of headroom. However, they're both identical combos. I don't know what would happen with two different combos. I'd say give it a try with an ordinary instrument cable, and see what happens.
     
  20. steve_rolfeca

    steve_rolfeca Gold Supporting Member

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    I have rewired various small combos so that the internal speaker plugs into the head via a jack on the back panel, instead of being hard-wired. The advantage is that you can use the amp interchangeably as a combo, a head, or an extension cab.

    In order to be safe, the wiring must be configured so that the internal amp's output cannot be shorted out, grounded, or connected to the output of another amp. Especially in these days of class D amplifiers, this requires some thought, and sometimes mandates the use of Speakon connectors.

    If you have to ask whether it's safe to connect two amps together via a common speaker jack, then you shouldn't be attempting that sort of mod.
     
  21. JTE

    JTE Supporting Member

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    Don't both amps have an effects loop, or preamp out power amp in connections? If so run a guitar cord from the FX send of amp 1 to the FX return of amp 2. Plug you bass into amp 1. Now you're using on preamp, and both power amps and speakers.

    John
     

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