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changing a tube in an SWR bass350

Discussion in 'Amps and Cabs [BG]' started by brianmharrison, Apr 6, 2009.


  1. brianmharrison

    brianmharrison

    Oct 11, 2007
    Atlanta
    All of my previous amps have been all solid state so I'm new to this tube thing. I'm pretty electronically inclined so I think I can do this my self.

    From what I've read changing a preamp tube is pretty easy and is just a matter of buying the right tube (in this case a Groove Tubes 12AX7A), opening the amp up, taking the metal cover off (if there is one), taking the old one out and putting the new one in holding it with a piece of cloth.

    Do I have it right? am I missing anything? Is there anything special I need to know before attempting to change the tube in a silverface SWR bass 350 (not x)

    I just want to make sure I don't screw anything up.
    Thanks!
    Brian
     
  2. 810wmb

    810wmb

    Jan 29, 2000
    you are correct...unplug the amp too.

    i changed the pre-tube in my bass 350 years ago. bought a nos something or other...i noticed a *slight* difference

    good luck!
     
  3. mrniceguy715

    mrniceguy715

    May 2, 2006
    oklahoma
    In the redface I had you just remove all of the screws that hold the case on and the rack handles. Gently remove the case as not to scratch it all up. Then (with the amp cool of course) pull the old tube out and firmly press the new one in place.
     
  4. Bardley

    Bardley

    Nov 16, 2007
    Louisville, KY
    And FWIW, you don't have to use a Groove Tubes. You can use any 12AX7 you want. They will all sound slightly different. I replaced the 12AX7 in my SWR SM-500 a few years ago with a Tung Sol and it really beefed up the mids. It also gave me a bit more gain. I loved it. I have also used the JJ/Tesla ecc83s and it sounds great.

    Lots of choices here:
    The Tube Depot - 12AX7

    It's very easy to swap them.
     
  5. I don't know if it will apply in your case, and I don't know where groove Tube sources their 12AX7A's from, but if you look at my recent post you will see I found a massive difference in tone by using a different make (in my case a 12AX7AEH from Electroharmonix). I may just have had a dud tube, but the GT was dull, lifeless, and didn't have much top end. I have since read several reports of GT's being not of the best sound-wise, depending on source (they don't make their own). It MIGHT be worth your while to read reviews of the various makes of 12AX7A, and choose one other that GT. I was sceptical about different makes sounding very different if they are the same valve, but believe me, mine was like night and day. Just a thought. And yes, that's all you have to do.
     
  6. JimmyM

    JimmyM

    Apr 11, 2005
    Apopka, FL
    Endorsing: Ampeg Amps, EMG Pickups
    Groove Tubes take tubes from other companies and rebrand them, so you're only paying for the logo. Get tubes from a company that makes their own, like Tung Sol or JJ and save a couple bucks. Having said that, I've bought GT's many times because they're always available at Sam Ash or GC ;)
     
  7. brianmharrison

    brianmharrison

    Oct 11, 2007
    Atlanta
    Thanks for all of the help guys. So different brands of the same tube will sound different as well? I'll have to do some more research on that.
     
  8. ettsn

    ettsn

    Mar 29, 2009
    Atlanta, GA
    Also, make sure you leave no fingerprints on the new tube. Finger oil can sometimes (although not common) cause a hot tube to shatter.

    My preference in 12AX7 tubes is one of the Russian brands, like Svetlana or Sovtek.
     
  9. not only will they sound different, they'll perform differently. some are more durable than others, etc. the old GE and RCA tubes are famous for being unbelievably durable. quite a lot of the ones made in the 50's are still in use today

    i did a brief comparison of different tubes in my svt preamp, the sound clips are down right now while i change hosts but i should have them back up in a couple days. in the meantime the tube descriptions may help your decision-making process. thread is here

    for a good, cheap, all-around tube i recommend sovteks. groove tubes are just terrible, and sovteks are around the same price. you can go berserk and spend all kinds of money on NOS GE and Telefunkens but you're not going to hear a huge difference, especially gigging. i generally only pop my GEs in when i'm recording and such
     
  10. brianmharrison

    brianmharrison

    Oct 11, 2007
    Atlanta
  11. Bardley

    Bardley

    Nov 16, 2007
    Louisville, KY
    FWIW,
    I bought my Tung Sol from Music123 and they shipped it to me in a non-padded bag. :eek: Not even bubble wrap. I did complain to no avail. One of the contacts was bent and the small box was completely crushed as well. I would order from another place. The Tube Depot is a few bucks more, but it was nicely packaged.
     
  12. brianmharrison

    brianmharrison

    Oct 11, 2007
    Atlanta
    definitely good to know...won't be ordering a tube from music 123 then. So, I think I'm going to go for the Sovtek 12AX7WA unless anyone else wants to weigh in....
     
  13. just an update to let you know that the sound clips are back up so you can listen for yourself

    listening to the GE clip again....man i love those tubes. just warm enough, just gainy enough. full, full-range, creamy and beautiful

    couple of interesting ebay auctions for some NOS stuff. dunno how many tubes are in your rig, but 4 is usually enough for most preamps

    NOS GE tubes for cheap

    NOS RCA tubes for cheap

    both decent buys and DAMN fine tubes. if i wasn't saving up for a trip to romania (and if i didn't already have a dozen NOS GE tubes laying around), i'd be on those GE tubes like white on rice
     

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