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Tube Amp Power rating

Discussion in 'Amps and Cabs [BG]' started by ElephantTalk, Apr 13, 2005.


  1. ElephantTalk

    ElephantTalk

    Jan 20, 2005
    Indy
    I've had this question for quite some time now, so I'll just fire it out.
    I've got a Mesa Boogie Buster 200 head. Rated at 200W.
    Well it's only got 6 - 6L6s in the power section. Each of these tubes is rated to output only 25Watts, maybe 30W in melt-down.
    So how is this capable of 200W?

    6x25 = 150

    The same goes for an Ampeg SVT-II.
    It uses 6 - 6550s which meltdown at 40W, but it's rated at 300W.

    6x40 = 240

    What gives with the misguiding?
    Or am I missing something?

    -ET
     

  2. 6l6s in class AB are good for about 25W each absolute maximum (more like 22 for most variants). the Buster is a 150W amp at best.

    Most 6550s in class AB can do about 50W or more. Some variants get more, some less depending on the devices and the plate voltages. My SVT with 6 GE 6550s, does 345W clean.
     
  3. James Hart

    James Hart

    Feb 1, 2002
    toms_river.nj.us
    Endorsing Artist: see profile
    6550/kt88 aren't peaked at 40watts. The Trace V6 has 6 of them and rates at 400 watts RMS. My amp has 8 KT88 and benched at almost 450.

    Different designs yeild different output too.
     
  4. James Hart

    James Hart

    Feb 1, 2002
    toms_river.nj.us
    Endorsing Artist: see profile

    True, plus Mesa likes to quote PEAK watts for it's tube amps.
     

  5. KT-88s are capable of more output than 6550s too, which is why they can get 400W out of the V6. If you put 6550s in it, it would be nominally 300W...
     

  6. Like 500W for the 400+ which is really a 300-? :D

    Disclaimer: I'm not slagging the 400+, it's a fabulous and loud amp, it just ain't 500W no matter which way you slice it...
    :D
     
  7. ElephantTalk

    ElephantTalk

    Jan 20, 2005
    Indy

    Ah, ha....that's the answer i was looking for.

    I guess I was quoting a C-class 6550 at 40Watts.
    This must also be where you make the jump from a $50 6550 to a $150 one.
    I'm a noob with all of this tube stuff, but I do like to learn. :p

    How do you know which tubes to buy?
    I mean Mesa says that you should only use their tubes.
    Would I need to take my amp to a tech to install brand new tubes if I were to order some TAD 6L6WGC-STRs from "thetubestore"?

    -ET
    BTW...thanks for the info.
     
  8. BurningSkies

    BurningSkies CRAZY BALDHEAD

    Feb 20, 2005
    Seweracuse, NY
    My advice is to ignore Mesa on that angle. While you can use their tubes, they're just rebranded matched sets. If you talk with a reputable tube dealer (there are lots, and everyone has their own preferences), and tell them what you're looking for in what kind of amp they should be able to put a set together for you. My experience is that most dealers will have dealt with your amp before unless its a completely obscure one.
     
  9. BurningSkies

    BurningSkies CRAZY BALDHEAD

    Feb 20, 2005
    Seweracuse, NY
    Most (if not all ) Mesa's are 'fixed bias' amps, meaning you can't adjust the biasing for different tubes...pretty much plug and play. You can get someone to mod your amp to adjust tube bias, but if you're not gonna change out tubes a ton and you're not playing lots n lots, then it's not worth it really.

    If you're not comfortable with the notion of opening up the back of your amp and doing it yourself, or if you're uncomfortable with handling tubes, take it to someone.
     
  10. 7thbass

    7thbass

    Nov 21, 2003
    Houston, Tx
    I think they were talking about Class AB amp design, not the quality of tubes. WTFDIK? Am new to tubes as well.