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Bias question (Bugera 333XL)


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  • Bias question (Bugera 333XL)

    Hey Guys, got a Bugera 333XL on the cheap over the holidays, and though it does not sound broken, it just sounds off.

    The EQ works on the highs and mids, but the low doesn't seem to make much of a difference, and it's lacking a lot of low end. It's also very noisy, not hissy or crackly, but when I try to get the volume up it feeds back a lot more than my other amps even with moderately low gain settings on both crunch and Lead.

    I suspect it needs biasing but I've never had an amp that was so out of bias, or that the tubes were so ar gone that it sounded this thin and weak. But I've also never had an amp with an active EQ, so don't know if that has anything to do with it.

    Any help would be greatly appreciated. Also any similar experience from current 333XL owners would be nice too.

    I realize it's a Bugera, so be gentle

  • #2
    What in particular makes you think the problem is inaccurate biasing and not, say, a faulty preamp tube or some other problem...?

    Bias being off would likely just either moderately increase crossover distortion (you would hear a faint buzz on each quietly picked note) - assuming the bias was on cold side - or just make the amp run hotter - if the bias was on the hotter side. It shouldn't effect the preamp signal a bit and certainly would not have anything to do with bass control not having a lot of range or amp being overly feedback prone.

    Yep, it's a Bugera it's probably more reliable than most of the modern Marshall amps.
    Honestly...this is not music... it is hatred and self loathing expressed with loudness.


    • #3
      Any idea how old the amp is? Probably power tubes. That Bugera bias probe point is like Peaveys & is not a proper way to bias it.

      Get a Eurotubes probe - it plugs directly into the tube socket -this will explain it.

      Bugera stock preamp tubes don't break up well either. Just a simple preamp tube swap out in V1 will greatly improve the tone.

      Yeah, I can see the Bugera haters comin'.

      Most old trusty amp companies don't build them like they used to either....


      • #4
        Id guess its tubes, but probably not a biasing issue.
        Peavey ESP DiMarzio

        I get my tubes from should too!!

        Good Transactions


        • #5
          When I got my 6262, it sounded like middy, microphonic ass. I swapped all the preamp tubes and it improved 1000%. Do that first for sure.


          • #6
            Thanks for the replies.

            I eliminated the preamp tubes because when I bought it it had all new JJ ECC83 gold pins recently installed in it (according to the previous owner), and just to be safe I replaced them with others I had around anyway, but to no avail.

            I've never had an amp that sounded this off just because of biasing/old tubes so am pretty unfamiliar with the effect it has. I've recently read some articles about these and I think I need to pull the chassis and check for loose or burnt connectors and possibly loose grounds and mounting screws. Not sure how old this one is but these issues seemed to be common on the earlier production runs.

            Thanks everyone for being so level-headed, I really expected a lambasting for even asking about a bugera

            I can tell that there's potential with this amp. And the clips I've heard I really like. Your answers have pretty much confirmed what I thought about bias' influence on tone. I'll crack open the chassis at least by this weekend and post anything I find, especially if it solves the problem.