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Would this work, or just blow up?

Discussion in 'Amps and Cabs [BG]' started by The Sound of the Police, Aug 26, 2001.


  1. This is a rather strange idea I had; I hope I can explain it. I'm using a GK 400RB head. This has two outputs; each 200 watts. Can I take a Y cable and plug the two-end-side into each output of the head and the other side into my cab, therefore running 400 watts into my cab? Or is this just a bad idea?
     
  2. Luis Fabara

    Luis Fabara

    Aug 13, 2000
    Ecuador (South America)
    Audio Pro - Ecuador
    1) Your head is rated at 200 Watts at 4Ohms. Both Outputs are parallel.

    2) Doing what you think will actually do NOTHING DIFFERENTAs it will act as 1 Cable, because those 2 Outputs are parallel.
     
  3. This makes me think: why are amp manufactorers always so incredibly vague about their outputs? I mean, as for all TheSoundOfThePolice knows, the amp is a dual (eg stereo) amp with 2 outputs, each rated 200 watts.

    Strange people. Those amp designers.
     
  4. White_Knight

    White_Knight

    Mar 19, 2000
    USA
    The Gallien-Krueger 400RB III is rated at 240 watts at 4 ohms, 150 watts at 8 ohms. If you have an 8 ohm cab, you'll only be sending the 150 watts to it. If, however, you have a 4 ohm cab, you'll be getting the amp's full 240 watt output. As Luis pointed out, the outputs are wired together in parallel. Thus, it doesn't matter if your using a single cable to send 240 watts to a cab (or cabinents) or two cables. Either way, no matter if you using one cable or two, if you have an 8 ohm cab, you'll only get 150 watts. If you have a 4 ohm cab, you'll be getting the full 240 watts.

    http://www.gallien.com
     
  5. The impression that I got was that each output was feeding out 200 watts, so that if you use both you are pumping 400 watts altogether, which is why it's the 400RB. This is wrong?
     
  6. I think you might be. Don't get caught into the trap of model numbers ~vs~ their outputs...for example a GK800RB does NOT put out 800w (or close)...

    The rating (240w/4, 150w/8) is SHARED across the outputs (bi-amped amps, where there are two separate amps providing separate power, are different beasts).

    So, this is what you'd get if you plug in:

    1 x 8ohm cabinet = 150w (one speaker output)
    1 x 4ohm cabinet = 240w (one speaker output)
    2 x 8ohm cabinets = 240w (two speaker outputs)
    2 x 4ohm, or 1 x 8ohm + 1 x 4ohm cabinets = dead amp (unless your amp can handle a total speaker impedence of <4Ohms, which the GK cannot).

    So you see the 2 outputs are there to enable you to connect 2 8ohms cabinets for a total power of 240w (4 ohms). If you already run a 4 ohm cabinet then there's nothing much else you can do, short of increasing the number of speakers (eg replace a 4ohm 4x10 with a 4ohm 8x10).
     
  7. I have an 8 ohm cab (SWR Workingman 4x10). So if I understand this correctly, if I got another of the exact same cab, it would be more than twice as loud? There seems to be a lot I don't know about amps.
     
  8. JMX

    JMX Vorsprung durch Technik

    Sep 4, 2000
    Cologne, Germany
    No, you wouldn't even get twice the power (240/150=1.6), so you get less than 3dB extra volume.
    Twice as loud would be +10dB, but you'd need 10 times the power to get it.
     
  9. EString

    EString

    Nov 20, 2000
    Los Altos, CA
    Silly rabbit.
     
  10. With 2 8ohm 4x10 cabinets, while you won't get "twice as loud", you'll certainly notice an increase in volume (slightly more watts, but the extra speaker surface area is where the money is).

    The bonus with another cabinet is that (in theory!) you won't have to turn up quite as loud, and generally not have to run the amp at 11 to get a decent volume.

    If you need more volume, i'd look into a new amp head first, perhaps a GK800RB.
     
  11. Thanks everyone. I think I understand it now.