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Big Block 2ohm warning

Discussion in 'Amps and Cabs [BG]' started by rekesbass, Feb 3, 2005.

  1. this past weekend I was playing a gig with another band(a double bill,if you will)and the bassist from the other band and I decided that using one rig would be good for both of us since we both have the same rig(BB750 and15" scout cab 4ohm). We also thought that using both of our cabs(2ohm load) would be a really good idea..everything was going good until my head went up in smoke about a half-hour into their set.luckily the other bassist had his head with him,so we swap out heads and guess what happens 20 minutes into my bands set?? his head also burns up..We're both coverd under warranty,but I think Mesa should re-think the ohm rating on this amp and I strongly reccomend that nobody do this with their BB750(or any other of the m-pulse line)...this is not the first time this happend to me with the BB..My very first gig with the BB I ran a 2ohm load and fried it,but I thought that maybe I got a lemon.I brought it back where I purchased the head and it was fixed under Mesa warranty with Mesa parts and all was well until this recent gig,so that only leads me to believe that this amp can NOT handle a 2ohm load....On a side note,the store gave me a loaner(used bass 400..not the 400+) to use while my BB is being fixed and noticed that the tubes are(6) Electro Harmonix 6L6EH and not the 6550's that I think are supposed to be in there. my question is..what tubes are supposed to be in a bass 400 ? and will it be at full power with the tubes that are in there now? I don't want to have any issues with an amp I don't even own...should I bring this issue to the store owner..I'm really hoping someone could shed a little light on this tube issue(a-hem PsycoBG cough)...thanks all..
  2. Joe Beets

    Joe Beets Guest

    Nov 21, 2004
    That does it for me, I'm going with the SVT6-PRO. For my backup/practice head I'll get an Ashdown MAG600R. I know Bass Northwest sells Ashdown, I hope they do Ampeg too. :smug: :smug:
  3. silky smoove

    silky smoove

    May 19, 2004
    Seattle, WA
    Wow, I thought that Mesa wouldn't have put that on the amplifier if it weren't safe. I know my M-Pulse 600 says that it can go down to a 2 ohm load (its printed right next to the speaker outs), but I have yet to try it. I think I'll just stick to a good old 4 ohm setup and not worry about it.

    Has anyone else tried running a Big Block or M-Pulse down at 2 ohms? Where's Benjamin Strange?
  4. kjones


    Dec 4, 2004
    Ran my Mpulse 600 on a hot summer day for about 12ish hours outside in the sun at 2.67 ohms without a hiccup.
  5. Folmeister

    Folmeister Knowledge is Good - Emile Faber Supporting Member

    May 7, 2003
    Tomball, Texas
    Write in to Bass Player and let them know! They just did a product review on that unit.
  6. tombowlus

    tombowlus If it sounds good, it is good Gold Supporting Member

    Apr 3, 2003
    Fremont, Ohio
    Editor-in-Chief, Bass Gear Magazine
    That is a really scary story! Three BB 750's going down with a 2 ohm load! Wow!

    Thank you for sharing this story and for urging caution when using Mesa Boogie amps with a 2 ohm load. The weird thing is that they advertised the 2 ohm capabilities of the BB, and it seems to be problemmatic, when they didn't really advertise the 2 ohm abilities of the Walkabout (though the manual sort of says 2 ohms is okay), and myself and many others have run the Walkabout into a 2 ohm load with no problems. In fact, my Walkabout has never even thought about getting hot with a 2 ohm load.

    Interesting - but scary - stuff. I hope you end up with a working head to your liking.

  7. Benjamin Strange

    Benjamin Strange Commercial User

    Dec 25, 2002
    New Orleans, LA
    Owner / Tech: Strange Guitarworks
    I seriously doubt that the problem was the ohmage. I think something else must have been wrong - they're are quite stable at 2 ohms. Heck, my Walkabout isn't supposed to be stable at 2 ohms, and yet it handles it without a fuss.

    If you could manage it, I'd try to keep that 400 if I were you. Those are pretty damn sweet. They are supposed to be 6550's in there, but the 6l6's will work ok too, with a little bit less headroom.
  8. I got word from the tech guy that the mosfets fried..I am not a tech guy,but two times I ran a 2ohm load and two times I burned it up...I also had a 600,and was able to run a 2 ohm load with no problem..I don't understand why the amp reccomended for 2ohms would break and the amp reccomended for 4ohm would hold up,and it was'nt just my amp that burned up,my friends 750 burned up also that same night...BTW,I had a chance to gig with the bass 400 twice since last weekend, and I LIKE this amp VERY MUCH. I really would like to keep it,but I don't want to give up my warranty or take the financial beating on trading in my brand new amp for a used one.(I will ponder this more while I'm waiting for mine to be fixed)..Ben Strange,would'nt the 6l6's reduce the power of the 400 by half since they are only capable of 25 watts?(25x6=150)as opposed to the 50 watts made by the 6550's...I'm confused
  9. popinfresh


    Dec 23, 2004
    Melbourne, Aus
    Kinda off, but hey. What do you find is the main tonal differences between the 400 and BB750? No-one really gets 400's in around here, so i'm curious..
  10. toddmcm


    Jan 19, 2005
    Los Angeles CA
    Am I the only one that thinks this is a rather odd setup... ESPECIALLY FOR TWO guys to have at one club? Sounds fishey to me.

    a BIG BLOCK with a Scout Cab?

    I have one question - WHY?

    Anyhow for what it's worth I push a walkabout (which is only rated down to 4 ohms) at 2.67ohms through a single 15 and a 210 for hours on end.

    I'm curious to hear how it works out.
  11. Toddmcm, you ask why?.it's a really good combo, sounds alot bigger than a 1x15+tweeter,it's a great lightweight cab..I originally wanted to get 2 scout cabs but,could'nt afford the second one at the time.,over time I figured out I don't really need it,but wanted to get it at a later time for bigger rooms and the outdoor gigs..Now,the other guy and I are friends, we both have the same rig becuase he heard mine and saw how small it is and was impressed enough to get rid of his G-K bi-amped 2 cab set-up(1x15 and4x10).. I've had mine since april '04' he got his around aug. or sept.,he bought two cabs and only experienced a 10 second cut-out in sound,but came right back quickly,did'nt even need to re-power the amp and it only happened one time...On this paticular gig,my gear was already at the club from the night before so we dicided that we would combine our rigs.He agreed to bring one of his cabs and it was great until the amps went to the great gig in the sky..I'm not worried,I know that Boogie will make good on it,I just wish that it did'nt take soooo long to get the parts here because I'm really diggin the Bass400 and I don't want to start gassin for somethin new...BTW...popinfresh,the bass 400 is alot like the 400+,minus one graphic e.q. slider and the ability to load down to 2ohms...the big block is a different animal, but is closer to the 400(+)tonally than the m-pulse600...maybe because there are more tubes in the bigblock,but it seems to sit somewhere between the 600 and the 400(+)..tubey but tight..and the o.d. is real useful with the gain and master controls. Overall I'm happy with the BB,but this 2ohm issue has got me concerned..I don't think I'll ever attemped it again..