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Preamp tubes

Discussion in 'Amps and Cabs [BG]' started by nastyn8c, Apr 16, 2005.


  1. nastyn8c

    nastyn8c

    Feb 7, 2005
    Tampa, FL
    I use an SWR SM-400S. I like to add a lot of bass to my sound using the preamp, but it winds up clipping. I can turn the gain down on the preamp, but I'd rather not.

    It has whatever brand 12AX7 SWR was using when it was manufactured.
    What I was wondering is whether or not putting in a new, better, preamp tube would help. If it would, what type of tube should I use? I can't afford anything much more than $30, so please don't tell me to go get a Telefunken. I was thinking about going with an Electro-Harmonix, but I really want to know if that would even help.
     
  2. JJ Electronics 12AX7's are MUCH smoother sounding tubes and they're cheap. If you want more bass, with less mids, they're the way to go.
     
  3. nastyn8c

    nastyn8c

    Feb 7, 2005
    Tampa, FL
    I'm really more concerned about volume than anything else, but it does need to be able to handle a lot of bass and low mids...
     
  4. IvanMike

    IvanMike Player Characters fear me... Staff Member Supporting Member

    Nov 10, 2002
    Middletown CT, USA
    it could be that you're plain old giving the preamp way too hot of a signal with all those bumped lows and low mids, and no matter what tube you put in it (or what preamp you use) you're going to be clipping it in short order.
     
  5. Theres a point

    Try running it into the -15dB or whatever bit, or try turning down the volume on your bass and let the amplifier amplify :cool:
     
  6. Finger Blister

    Finger Blister

    Jul 8, 2003
    +1


    Whether you use a 5751 or a 7025 the 400-S will clip at about the same position.

    However a good preamp tube is a good thing for that amp.

    A NOS tube from Europe or the US would be an improvement.

    Avoid Chinese or Eastern European crap.

    Avoid the "Multiple Bass Boost Trap."
    -Boosting the Aural Enhancer
    -Boosting the Bass
    -Boosting Bass again or even twice more at the Parametric Mid's.
    -AND Boosting Bass with an active instrument preamp.


    Believe It or Not:

    I've found that gain staging the 400-S with a rackmount compressor
    in the FX loop will give noticeable jump in apparent volume.
     
  7. Steve

    Steve

    Aug 10, 2001
    SWR stuff is kinda tube sensitive. You'll hear a difference.

    You can get a good used telefunken off Ebay for about $45. and it worth waiting for.

    Having said that, I don't think a better tube is going to help your issue.
     
  8. IvanMike

    IvanMike Player Characters fear me... Staff Member Supporting Member

    Nov 10, 2002
    Middletown CT, USA
    re-looking at your post i notice that you're boosting bass on the preamp itself. IIRC, the eq on swr is all post-tube gain stages. changing the tube won't help at all in that case.
     
  9. nastyn8c

    nastyn8c

    Feb 7, 2005
    Tampa, FL
    Thanks Ivan. That may very well be true, but I have noticed that if I turn the bass on the EQ up, it clips sooner. And it makes a huge difference. Perhaps my EQ is pre-tube gain; the amp is about 9 years old. I don't know, but I will look further into it. Thanks everybody.
     
  10. IvanMike

    IvanMike Player Characters fear me... Staff Member Supporting Member

    Nov 10, 2002
    Middletown CT, USA
    actually, i think the clip on that unit is post eq, so it indicates the entire preamp clipping, not just the tube stages.
     
  11. Groovetubes 12AX7M (Mullard copy) for $19 has big clear well defined low end and is in your budget.
    http://www.torresengineering.com/newgroovtub11.html

    I have tried the EH 12AX7A, 12AX7M, and now the NOS RCA Blackplate 12AX7. The RCA is the best but the GT 12AX7M is right behind. You will find more headroom as well with the 12AX7M.
    Gary
     
  12. The "Mullard" copy has proven VERY unreliable and mechanically unstable. It's a WASTE of money, IMO.
     
  13. Finger Blister

    Finger Blister

    Jul 8, 2003
    +1

    The Psycho knows...
     
  14. tombowlus

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

    Apr 3, 2003
    North central Ohio
    Editor-in-Chief, Bass Gear Magazine