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6 ohm load on a boogie 400+ ??

Discussion in 'Amps and Cabs [BG]' started by mactac, Jan 23, 2006.

  1. mactac

    mactac Supporting Member

    Nov 28, 2005
    Victoria, BC, Canada
    ok, so with this amp, there are 6 speaker sockets. 2 for the 2 ohm, 2 for 4 ohm, and 2 for 8 ohm.

    if you hook up 1 8 ohm cab, you hook it up to a 8 ohm output. if you hook up 2, you hook them up to the 4 ohm jacks (as the laod is now only 4 ohms)

    What do you do when you have an 8 ohm and a 4 ohm cab? THis equates to a load of 6 ohms...?

    hook them both up the 4's? both to the 8's? one to the 8, one to a 4?

    anyone know definitively?
  2. pepsican


    Oct 23, 2004
    Actually an 8 ohm load and a 4 ohm load would be 2.67 ohms.
  3. Your load is 2.67 ohms, not 6 and you need to hook them BOTH to the 4 ohm output jacks (or run a cable from one 4 ohm jack to one cab and another cable out of that cab to the other- same difference). You MUST NOT try to "mix'n match" and use different value output jacks.
  4. mactac

    mactac Supporting Member

    Nov 28, 2005
    Victoria, BC, Canada
    why not hook them up to the 2 ohm jacks?
  5. Kelly Lee

    Kelly Lee Yeah, I'm a guy! Supporting Member

    Feb 17, 2004
    Marana, AZ, USA
    Tube amps are the opposite of SS amps. Where SS you don't want to go lower than the recommended minimum, with tube you do not want to run a higher impedenance.

    If your load is 2.67 then the safest tap to run from would be the 4 ohm tap. If you ran it from the 2 ohm tap you will more than likely burn out the output transformer (among other things) IIRC.
  6. Tim1


    Sep 9, 2005
    New Zealand
    That's interesting. When I had my old SVT2 non-pro and wanted to run a single 8ohm cabinet off it Ampeg advised me that it would cause no harm running it with the amp set to 4 ohms.
  7. Kelly Lee

    Kelly Lee Yeah, I'm a guy! Supporting Member

    Feb 17, 2004
    Marana, AZ, USA
    Hopefully Psycho Bass Guy will pop back in to correct me if need be.
  8. Call Mesa. I asked them the same Q.

    From a rather foggy memory I believe I was told to run the 8 ohm cab to the 4 ohm tap and the 4 ohm cab to the 2 ohm tap. On the road and don't have the note in front of me so give them a call.
  9. jujube_2a


    Jan 18, 2006
    Corsica, France
    Keep in mind that with different impedances, the cabs will not get the same amount of power.
    For example, with 300 watts of total power @ 2.67 ohms, the 4 ohms cabs will get 200 W and the 8 ohms one will get only 100 W
  10. I hear the phrase "burn out the output transformer" FAR too often. While it is correct that you need to go with rated loads or lower, it is the tubes that will die LONG before the output transformer, although their death will probably cause some serious OT damage. I'm not disagreeing with the advice, just the supporting logic.

    If they told you that, there's a SERIOUS problem because that WILL damage the amp.

    The amp is not solid state and has an output transformer to deliver the same power at different rated impedances. What this says is the opposite of reality.
  11. Yup, found it. That's exactly what I was told by Mesa; 8ohm cab to the 4ohm tap, 4 ohm cab to the 2 ohm tap.

    Has not caused any problems.
  12. You're either extremely lucky and/or your amp is biased VERY cold because splitting loads on two taps is NOT a good idea. The 8/4-4/2 setup may also be helping you- doubling the secondary impedance jacks up the plate voltage and raised your outpower with increased instability, but using multiple taps lowers it (and your output power). I STILL say it's a bad idea.
  13. Must be the clean living! Actually haven't used it too much in that manor so I'm sure that helps matters.

    Not happy about the bad advice from Mesa though.