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Mesa 400+ impedance question

Discussion in 'Amps [BG]' started by ariff, Dec 10, 2012.


  1. ariff

    ariff Supporting Member

    Joined:
    Nov 28, 2007
    Location:
    Lawrence KS
    So the 400+ has two output taps on the back marked 2 ohm, two marked 4 ohm and two marked 8 ohm the idea here is it you are running 2- 4 ohm cabs you hook them to the 2 ohm taps to present the amp with a 2 ohm load likewise with two 8 ohm cabs run hook them to the 4 ohm taps. What should I use if I am running a 8 ohm and 4 ohm cab together which total around 2.6 ohms?
    Thanks!
     
  2. MAMMOTHvolume

    MAMMOTHvolume

    Joined:
    Apr 29, 2009
    Location:
    sheffield, uk
    What are the cabs? I wouldn't recommend running different impedance cabs in most cases
     
  3. ariff

    ariff Supporting Member

    Joined:
    Nov 28, 2007
    Location:
    Lawrence KS
    2x10 avatar and 1x15 avatar.. 2x10 is 8 ohms and the 1x15 is 4 ohm. Been running these cabs with several different heads (Peavey and Carvin) without any issues ever. Just picked up the 400+ on CL a few weeks ago which will mainly be used with my Power House 8x10.. But for smaller gigs which require us to lug gear up stairs I like to use the 2x10 and 1x15..
     
  4. Downunderwonder

    Downunderwonder

    Joined:
    Aug 26, 2009
    Location:
    New Zealand
    You're onto it.
    With tubes it's generally better to run under the rated tap impedance than over it. In this case 2.6 is so close to 2 it probably wouldn't stress things too much but tough call to make.
     
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  6. Bassmec

    Bassmec

    Joined:
    May 9, 2008
    Location:
    Ipswich UK
    Disclosures:
    Proprietor Springvale Studios
    If the 400+ is not fixed variable bias modded?, its such a cold running amp on its tube set, it would do no harm to run it at 2.6 ohms on the two ohm tap and I am usually a bit of a stickler for not messing with tube amp output tap/speaker matching impedances.:bassist:
     
  7. ariff

    ariff Supporting Member

    Joined:
    Nov 28, 2007
    Location:
    Lawrence KS
    OK good to know.. This is my first tube amp so I am still learning about them. I actually think I have a 8 ohm 15" speaker in another cab I might just switch them out to be safe. And no the amp has no bias mods done to it. It is stock fixed bias..
     
  8. NecroticImbecil

    NecroticImbecil

    Joined:
    Aug 20, 2004
    Location:
    under your bed
    IIRC There was mention of your situation in the manual, which the last I knew was still available for download on Mesa's web site.
     
  9. Brookdalebass

    Brookdalebass Supporting Member

    Joined:
    Jan 15, 2009
    Location:
    Northern CA
    Yikes. Now I'm confused. I've been running my 400+ with two 8 ohm MarkBass cabs (4x10 and 2x10). I plug one cab into the 4 ohm output of the Mesa and take a Speakon from that cab to the other...two 8-ohm cabs in parallel...isn't that presenting the amp with 4 ohms?
     
  10. nicoli

    nicoli

    Joined:
    Apr 4, 2002
    Location:
    Rockland, Ontario, Canada
    Yes... so why the confusion?
     
  11. Brookdalebass

    Brookdalebass Supporting Member

    Joined:
    Jan 15, 2009
    Location:
    Northern CA
    Thanks, Nicoli...ariff's original post kind of made me think I was doing something wrong...my 400+ sounds great and is actually louder and much meatier than my MarkBass Tube 800 head through the same cabs.

    I started my bass playing career with tube amps but switched to solid state...then hybrids: Hartke, Ampeg, Eden, Aguilar, Mesa...always felt something was missing. Got the Mesa 400+ a few months ago and found out what that missing link was.
     

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