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..