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Mesa Bass 400 "6L6" vs "6550" version?

Discussion in 'Amps and Cabs [BG]' started by chaosMK, Aug 21, 2005.


  1. chaosMK

    chaosMK

    May 26, 2005
    Albuquerque, NM
    Hi-fi into an old tube amp
    I was browsing around for possible replacement tubes for my recently acquired Bass 400 since it seems like its been acting up, and came across this info-

    Found on "http://www.musicparts.com/products.asp?Company=Mesa+Boogie"

    Mesa Boogie Bass 400 (6550 version) Tube Amplifier Schematic
    Contents: Schematics, Introduction / Features, Controls, Functions & Theory of Operation ($15)

    Mesa Boogie Bass 400 (6L6 Version) Amplifier Schematic
    Contents: Schematics, Introduction / Features, Controls, Functions & Theory of Operation ($15)

    Does anyone know anything about these different "versions" ? I rememebr someone recently retubed their 400 (that originally had 6L6's in it) with 6550's and said the bais appeared to have been set for 6550's.

    My 400 was made in 1982 and the original tubes in it are Mesa STR-415's.
     
  2. Chef

    Chef Moderator Staff Member Supporting Member

    May 23, 2004
    Columbia MO
    Staff Reviewer; Bass Gear Magazine
    I believe that Mesa 400's ran 6 6550's.
    Mesa 400+ ran 12 6L6's. At least my 400+ did...
     
  3. BurningSkies

    BurningSkies CRAZY BALDHEAD

    Feb 20, 2005
    Seweracuse, NY
    I believe that you can change the tubes without any modifications between the two types. You might want to do a search here for more information, and I'd maybe drop Tom Bowlus a PM as he's got a 400, talked about changing the tubes, and is knowledgeable about most things amp.
     
  4. there is no bias pot as standard on those 400's

    they can use 6550s and have a ~300 watt output, or 6L6's and have ~150 watt output

    apparently the 6550's sound better and they also have the bonus of being louder :)
     
  5. Matt H

    Matt H

    Jul 30, 2005
    Ithaca, NY
    Don't bother spending 15 bucks for a schematic, there's one available on the web for free... I'll throw a link in if i can find it while writing this message.

    anyway- the 6L6GC's will give less power out, but that's not always a bad thing. the 6550's will have higher headroom (which may or may not be what you're looking for).

    Mesa doesn't believe in having adjustable bias in their amps (possibly on every model?). This is a good and bad thing. On the one hand, it makes "popping in a new set of Mesa tubes" easy...

    but what it really means?
    they bias everything very cold. For really high wattage bass applications this might not be a terrible thing... but your tubes are DEFINITELY not running anywhere near optimal.

    Oh, here's a link to the site with the schematic- I'll let you find the schematic itself (just because it's a neat site, i don't feel bad making you navigate).

    http://www.tubefreak.com/

    Anyway- the schem has a couple of neat things in it that I didn't expect to see. mesa's notorious for having their "unique" amps be direct clones of someone else's product (the recto line being the most notable... ) but this amp is kinda neat. I particularly liked the fixed bias PI thing they're doing. well, quasi-fixed bias...


    Also- if you felt like playing around. a 12au7 in the v4 position could be really cool with that cold bias. anyway, i digress...
     
  6. the only good thing i see about not having bias pots is that it meant you had to get mesa tubes, well, you didnt have to, you were just recommended to :p
     
  7. Matt H

    Matt H

    Jul 30, 2005
    Ithaca, NY
    of course, the Mesa "branded" tubes are the same russian and chinese stuff that everyone else is selling and rebranding...

    any reputable tube dealer can find you a set of appropriately rated tubes- and generally for a TON less money than if it bears the "mesa" label.
     
  8. tombowlus

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

    Apr 3, 2003
    North central Ohio
    Editor-in-Chief, Bass Gear Magazine
    To the best of my knowledge, there is only one version of the Bass 400, and it was originally designed to run 6550's, but (rumor has it) as Mesa Boogie's supply of quality, inexpensive 6550's dwindled, they started running 6L6's. In the service manual for mine, it looks like the reference to using 6L6's was handwritten after the fact. But, my manual definitely states that you can run either (but I do have mixed feelings about doing this without a bias trim adjustment). If you can't find a schematic, send me an e-mail or PM, and I can copy my manual for you.

    Then again, they may be referring to the Bass 400 (originally designed to run six 6550's) versus the Bass 400+ (designed to run twelve 6L6's).

    Tom.
     
  9. cheezewiz

    cheezewiz

    Mar 27, 2002
    Ohio

    +1...Lord Valve hooked me up.
     
  10. the ones they used at the time were apparently good tho
     
  11. Matt H

    Matt H

    Jul 30, 2005
    Ithaca, NY
    at the time?

    sure, like 15 or 20 years ago... NOS USA tubes were still readily available- AND affordable then. (of course, with an additional upcharge for the mesa name, even then).

    nowadays, the only two new production options worth considering are the svetlana's (er, old svetlana, now "Winged C" or S.E.D. since new sensor bought the rights to the "svetlana" name out from under the company in the US) or if they fit (do they?) the JJ KT88's (virtually the same tube electronically, not quite identical though). I'd probably avoid the chinese ones (though I love the chinese kt66's).

    yeah- lord valve is a very reputable dealer. I just don't care for his politics and won't buy from him- but not for service/product reasons. I may give into that someday though, we'll see.
     
  12. danomite64

    danomite64

    Nov 16, 2004
    Tampa, Florida
    According to the guys at Mesa, it's 240 watts for 6550's, and 190 watts for 6L6's, and you get a bit more tone out of the 6L6's. I'm using 6L6's on my 400; I needed no rebiasing, and I have tons of power.
     
  13. 4Mal

    4Mal Supporting Member

    Jun 2, 2002
    Columbia River Gorge
    CAll Bob at Eurotubes he'll give you the skinny on the tonal differences of the 6l6 vs 6550. He's a good egg and has pretty decent pricing as well. I've retubed my guitar amps with him and have no complaints at all.
     
  14. Chef

    Chef Moderator Staff Member Supporting Member

    May 23, 2004
    Columbia MO
    Staff Reviewer; Bass Gear Magazine
    +1 for Bob. He's done me real right several times.
     
  15. aye, he put me in the right direction too :)
     
  16. usiel

    usiel

    Mar 28, 2003
    yeah he rawks...got some preamps tubes from him for my 400+.
     
  17. cheezewiz

    cheezewiz

    Mar 27, 2002
    Ohio

    I'll make you a deal, you buy from Lord Valve, and I'll eat some Ben and Jerries. ;)
    He recommended the Reflektor/Svetlana 6L6s for me, and they are working out very well so far.
     
  18. Matt H

    Matt H

    Jul 30, 2005
    Ithaca, NY
    reflektor svets? so you mean the Sovteks? interesting... i'm guessing that's the same as the EH stuff then?

    Reflektor and Saratov plants are generally feeders into the "Sovtek" (new sensor) family...

    the st petersburg factory puts out the old "Svetlana" now SED or "Winged C" stuff... the one exception i can think of is the ef86, which may or may not be out of production depending on who you talk to...

    as for LV and B&J... at least B&J hasn't publically suggested killing people of differing opinions on various net fora. Of course, if they did, then I *might* start eating more ice cream.
     
  19. cheezewiz

    cheezewiz

    Mar 27, 2002
    Ohio
    Supporting Mumia Abu Jamal is the same as publicly supporting killing cops....but politics aside.....

    Ya...Reflecktor Svetlanas. Supposedly the "better" output from the Reflektor factory, at least that's what I was told. I do believe they'd probably be akin to the EH. This isn't where I got them, but here's a little blurb I found regarding the tubes...
    svetlana/reflektor
     
  20. BurningSkies

    BurningSkies CRAZY BALDHEAD

    Feb 20, 2005
    Seweracuse, NY
    Yup. Bob is good people.

    My 400+ is filled with his tubes, and the 2 guitar players I play with in different bands have his Peavey 'classic' retube sets running and both have much better tone than stock tubes.