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Gallien-Krueger 400RB-III Help!!!!!

Discussion in 'Amps and Cabs [BG]' started by bh7697, Apr 8, 2009.

  1. bh7697


    Apr 8, 2009
    I got a sweet deal on a head and its sitting in my jam room as i speak. Unfortunately, i dont know what to do about a cab.

    It has 2 output jacks on the back, and is capable of pushing 240 watts @ 4 ohms into 1 cab or 150 watts @ 8 ohms into 2 cabs.

    I'm new to this, since ive been a combo playing guy so I have a few questions.

    I wanted to have a full stack of probably a 1x15 cab and a
    2x10 cab on top, running 8 ohms each. I don't have the money for the whole thing, just the 1x15 for now. Its a yorkville 1x15 extension cabinet, but it has 2 speaker inputs on the back. If i were to run 1 cable from the head to the cab, would i be running at 4 or 8 ohms? am i supposed to run 2 cables to the cab? Also i want to know if this applies to all cabs, also if i were to run a 4x10 4 ohm cab.

    Thanks alot, sorry for the lengthly question.
  2. DanRJBrasil


    Jun 10, 2007
    you have to check the impedance of the cab, usually is 4 or 8ohms
  3. DevilTheory


    Jan 6, 2009
    The 4 ohms and 8 ohms thing you mentioned doesn't work that way.

    2 8 ohms cabs hooked to it = a resistance of 4 ohms, and so you'd get the full 240 watts with 2 cabs.

    I'm not sure about that cab, but I'm pretty sure the other output is for another cab. You could run cables to each cab form the head, or a cable from the head to the cab and then another cable from the cab to the other cab. If both cabs are 8 ohms, with one hooked up it would be 8, and with both it'd be 4, whether they're in series or parallel.

    If I'm wrong, someone correct me please.
  4. JanusZarate

    JanusZarate Low End Avenger

    Feb 21, 2006
    Petaluma, CA, USA
    Easy enough... here's the explanation:

    Your Yorkville 1x15 is 8 Ohms, right? Use either speaker input from the cab, and either output from the amp. Doesn't matter which you use, but only use one. DO NOT run two cables! Anyhow, with just that Yorkville cab, you have an 8 Ohm load. When you eventually add a second 8 Ohm cab to the rig, connect that new cab directly to the amp (via the other output jack) and you'll have a 4 Ohm load.

    The other jack on your cab is most likely used for daisy-chaining cabs (the old-school way of using multiple cabs, back when amps only had one output). You won't need to use that other jack in most modern applications. Nowadays, we can run cabs in parallel by connecting them directly to the amp instead of to each other (as you can see with the outputs on your amp).

    Not all amps have multiple outputs, to be fair. But GK and other major brands usually provide two outputs on their amps, as many modern cabs only have one input jack and can't be run in parallel the old-fashioned way.
  5. mrkreuzschlitz


    Jun 30, 2008
    Dacula, GA
    The number of cables running from one cab to one head don't affect the impedance.

    If you had the 2x10 at 8 ohms and the 1x15 at 8 ohms, they'd be a 4 ohm load, but on their own only 8 ohms a piece. You could run the head to the 1x15 and then the 2x10 to the 1x15, but there's no reason to really do that...
  6. MIJ-VI

    MIJ-VI Inactive Supporting Member

    Jan 12, 2009
    Hi bh7697.

    Your Gallien-Krueger 400RB-III's manual (it's listed under 'Choose A Discontinued Product').
  7. Jack


    Sep 6, 2003
    Northumberland, UK
    Which Yorkville cab is it? It'll probably state its impedance on the back plate somewhere.

    The number of cables is immaterial.
  8. 62bass


    Apr 3, 2005
    The Yorkville 1x15" cabinet is almost certainly an 8 ohm cabinet. If you use it alone, your amp wwill be working into an 8 ohm load and capable of 150 watts or so. The Yorkville cab is fairly efficient and will play quite loud with 150 watts. I've owned a couple that I used with a 400RB. One by itself was enough for small rooms. A pair could handle anything except loud outdoor gigs, in which case I'd be going through the PA anyhow.

    The combination of Yorkville 1x15 and 2x10 cabs would sound very good with the GK.

    As others have said, go to the GK website and download a copy of the 400s users manual. It should clear up your misunderstandings.
  9. Martizmo


    Mar 26, 2009
    Metro Detroit
    Never plug 2 cables from your head to the same cab. That's a daisy chain.

    Take an ohm meter to the speaker cab.
  10. bh7697


    Apr 8, 2009

    That is exactly what i was asking, and you answered my question! Thanks alot.
  11. Jack


    Sep 6, 2003
    Northumberland, UK
    Why is this bad?
  12. 62bass


    Apr 3, 2005
    As long as the 2 cables come from the same power amp and are in parallel, as they usually are, and the 2 input jacks on the speaker cabinet are in parallel, as they usually are, there is absolutely no problem. It's a waste of a speaker cable though, because you don't need it. This is not called a "daisy chain" as the term is normally used around here. The extra output jack on your amp is for connecting another speaker cabinet in parallel. The extra jack on the speaker cabinet is for connecting another cabinet in parallel to the one you already have hooked up. Same thing either way, except using a cable from the amp to each separate cabinet cuts down on resistance some. It probably won't amount to anything you could hear in a bass rig as long as the speaker cables are kept short (most seem to be 5 feet these days) and the gauge of speaker wire is thick enough. I like to use 14 gauge speaker wire for the lower powered amps. 12 gauge for the 1000 watt monsters and speakon connectors rather than 1/4" plugs for high power.
  13. Jack


    Sep 6, 2003
    Northumberland, UK

    Heh. Cheers mate, but I know the answer, I said as much before: :)
    Was just waiting too see the rationale behind the post, too many 'facts' get bandied around TB with no basis in science.

    If all the speaker cables and internal wirings are 'as standard' then all of the speakers will be in parallel. It doesn't matter whether you were to use 1 or 100 cables between any output on the amp and any cab. Run one cab from each output, run into one cab then the other, two cables into the same cab. Doesn't matter at all to the circuit, its all the same. Two cables from two outputs into two inputs on the same cab is perhaps a little redundant, and you open up a whole can of bad if one of the cables is wired funny, but (all being well) it'll be as though you had one slightly thicker cable.
  14. JanusZarate

    JanusZarate Low End Avenger

    Feb 21, 2006
    Petaluma, CA, USA
    Jack: agreed, but that just goes back to my point: There's no good reason to run multiple cables to the same cab UNLESS you're using the second jack on the cab for the older method of running cabs in parallel.
  15. Jack


    Sep 6, 2003
    Northumberland, UK
    Of course, totally agreed. But 'no good reason' and 'never do it' are a bit different.

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