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Not digging my SWR much lately

Discussion in 'Amps and Cabs [BG]' started by TheGeneral, Apr 17, 2002.

  1. I've been doing several gigs back to back each week and switching between my SWR sm400s and Aguilar rig, depending on the size of the gig. The sound of the Aguilar is great and I love it, but when I use my SWR head for the small gigs, I really notice a big difference in sound--the SWR is tinny and harsh in comparison. Any suggestions on a small head or combo that sounds like Aguilar and that is also very portable?
  2. Lovin Bass

    Lovin Bass

    Feb 8, 2002
    Los Angeles
    What's your price range?
    With no upper limit we could suggest ALOT but I am guessing you are looking for reasonable suggestions.

    What aguilar rig do you currently have? Head? Cab? Preamp? Etc.
  3. stevekim


    Feb 11, 2000
    los angeles, ca
    before you get rid of that head, try replacing the preamp tube. i replaced the 12ax7 in my swr sm400s with an rca 7025 and later a JAN PHILIPS 12ax7 and it made a huge difference. the amp is much quiter, the highs are less harsh, and it has smoother tone overall. a good preamp tube only costs $20-35 so it's worth a try.

  4. i second trying the new preamp tube. when i replaced the preamp tube in my old bass 350 it really opened the amp up sound wise.
  5. the sm400s is a great amp, id try a different preamp tube also. it will change the whole coloration of the amp.i keep a collection of mullards, telefunkens, rca, and on and on. different tubes react differently in different amps,..........some great tubes occasionally are microphonic, in which case i will try another like tube to be sure i didnt count nout a great tube which just happened to be microphonic.
  6. Thanks, everybody for the suggestions. I'll try to get a new preamp tube installed and see what kind of difference that makes.
  7. Jon Burnet

    Jon Burnet

    Jan 21, 2001
    Memphis, TN
    i'd be intrested to knwo the outcome.
  8. Hey guys,
    Are the preamp tubes something I can install myself? If all it takes is removing the cover and yanking the old tube out and replacing with a new one then I can definitely swing that by myself. If the tube needs to be re-biased or there is a serious danger to digging in there myself, then I'll take it to a tech.
  9. ihixulu

    ihixulu Supporting Member

    Mar 31, 2000
    South Shore MA
    the pre tube is plug-and-play and it does have a significant effect on the sound of the amp.

    Hate to be the voice of doom but I doubt the SWR will ever be as warm and fat as the Ag.
  10. I agree with you, ihixulu about the sound, but I'll be partially satisfied knowing that I made the SWR sound as good as it can sound.
  11. stevekim


    Feb 11, 2000
    los angeles, ca
    i agree. changing the tube will never make the swr as warm and fat as the aguilar but, with the right tube, it can improve the tone for the better.

    changing the tube is easy. it's important to choose the right tube, though. i would suggest getting in contact with lord valve (anyone have his email address?) i got my NOS RCA (sylvania) 12ax7 tube from chuck moses ([email protected]) for $20 and i highly recommend it. tell him it's for an swr sm-400s, he'll know which one you're talking about.

    all you do to change the tube is:
    1) remove the seven or eight screws at the top of the unit.
    2) remove the four or five screws on the front panel, up near the top of the amp.
    3) remove the top lid, gently pull out the old tube and gently push in the new tube making sure it's seated securely.

    it's a piece of cake.

  12. OK, folks-
    I replaced the 5 year old stock Groove Tubes 12ax7 in my SWR sm400s with an RCA black plate 12ax7 the other day. After a test inside my home and after one gig with it, this is what I have found:
    1. The top end is definitely smoother
    2. replacing the tube was easy
    3. there is more noise now

    I didn't have a chance to record the sound before and after, which would have been the true test, so it is a little hard to realize the difference. The sound is not night-and-day different, however it was worthwhile and relatively inexpensive to do I suppose.
  13. stevekim


    Feb 11, 2000
    los angeles, ca
    there is *more* noise now? that's strange. here's an easy way i like to test tubes. with the amp outside of the rack, open up the top. leave the top off and switch tubes, make sure you power off before changing tubes though! :)
  14. Stevekim,
    I think you're right. I'm going to try to do a real test and record the sounds so I can instantly access them and see what the differences are. do tubes have a burn-in period where they must operate for a while to achieve their steady operating characteristics?
  15. stevekim


    Feb 11, 2000
    los angeles, ca
    i'm not sure about the burn in period. keep us posted on your findings. sounds interesting!

  16. tornadobass

    tornadobass Supporting Member

    Nov 20, 2000
    Iowa City, Iowa
    I agree about different sounds for different tubes with this amp. Mine came with a Groove Tubes ECC83. A GE 12AX7 produces a brighter sound, while a Telefunken has a warmer, smoother sound.

    When changing tubes, be careful not to overtighten the lid screws. Mine has a couple of oversize screws from stripped holes in the aluminum chassis.

    What can also make a difference in sound of this amp is how you use the aural enhancer. SWR example settings show the enhancer knob at half or more. I've been trying mine out turned on just a tiny bit and that gets rid of the boominess/bright edge with my EUB.

  17. Ty McNeely

    Ty McNeely

    Mar 27, 2000


    If you take the tubes out immediately after you've played the unit, the tubes will be *HOT*. Use an oven mitt or something similar to keep from burning your hand.
  18. General, I have noticed on my sm400s that you can get a little more warmth by using more pre-amp gain and less master volume . also back off on the aural enhancer along with the transparency knob. IMO the sm400s is a terrific head and worthy of being anyones backup (hell its my main head) . I personally have never found the head to sound harsh or tinny except when used with too much cab horn especially the SWR cabs so if youve got a horn loaded cab with attenuator control try backing that off too. Good Luck to ya
  19. one other thing, is that you should always run into the passive side even with an active bass (don't know if you are or not) but i think the passive section of most SWR amps goes through one extra tube stage than the active side.

    that's how my IOD works at least.
  20. tornadobass

    tornadobass Supporting Member

    Nov 20, 2000
    Iowa City, Iowa
    Add to Warwick5S's suggestion...only the reverse...if you run a passive bass into the active input, besides low gain, the low input impedance will result in a tinny, thin tone with some amps.

  21. Primary

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