Just retubed the SVT......

Discussion in 'Amps and Cabs [BG]' started by Mark Reccord, Mar 28, 2002.

  1. I just retubed my '76 SVT and had some resistors and diodes replaced. I put a full complement of Groove Tubes in (except for the 6C4 which was a NOS that my buddy had). OH MY GOD!! I thought it sounded good before. Now it's tighter, punchier and louder. The best way I can describe the sound is that it's like getting punched in the face :p:D. It's the first time I've retubed it (I've had it for about 18 months). My buddy who did the work says he's never seen one that old in as good shape. It's never been blown up which is rare! (Not yet anyway :D). Can't wait to jam....
  2. BFunk

    BFunk Supporting Member

    Hey, if you think it sounds good now, give it a couple of weeks, it will sound 10x better. Power tubes take some time to break-in. You'll be in nirvana.
  3. Funkster


    Apr 6, 2000
    Wormtown, MA
    I'm gonna have me one of dem someday!!!
    Good year to have!! I bet it sounds Sweet!!!!!
    I have a 76 Ampeg B25B (1/4 of the tubes and 55 watts) and that thing sounds nice! Only get to use it in the studio and when we do acoustic gigs!
  4. Leopold B.

    Leopold B.

    Mar 6, 2002
    Lawrence, KS
    Hey Spacegoat (or anyone), I have an SVT2pro that I think needs new tubes, the guy I bought it from hadn't retubed it in over a year, and that was a couple-few months ago. I can't get a good sound out of my E-string but everything else sounds good. Think new tubes would fix my lousy E? (the bass sounds fine on other amps.)
  5. BFunk

    BFunk Supporting Member

    Tubes should last about 2 years under light use. (By this I mean about 5-10 hours per week of play time, without really pushing them hard.) They will give out in a year under heavy, hard use. These times will also depend on how the tube quality, matching, biasing, and care. Driving cold tubes will reduce thier life significantly. You should wait at least one minute in standby, preferably 20 minutes or more. Also check the bias every six months.

    Dying tubes will loose luster, volume, and clarity. However, other issues can cause this. (A bad cap for example.) Best thing for you to do is have a qualified tube-tech look at it. (Keep in mind that very few electronics guys really know tubes.)

    What is cool is that power tubes often suddenly get very big sounding and punchy just before dying. This is usually accompanied by a very bright red glow of the voltage plates. My tube-tech friend calls this "going nova".
  6. Lovin Bass

    Lovin Bass

    Feb 8, 2002
    Los Angeles
    I was thinking of adding a tube amp to my arsenal. I love their tone but I was always concerned about the annual cost of tube replacement. Just out of curiosity, what would you expect to spend for re-tubing? My thoughts are around $250. Is this about right?
  7. BFunk

    BFunk Supporting Member

    I think you should get 18 months or more. Svetlana 6550-C's sell for about $50 a matched pair. I have 8, so I am looking at about $200. For a complete retube, I also have to add about $50 for the pre-amp tubes. (All power amps have a pre-amp section. That's where the volume control is.) If I have someone else do the work, add $50.00. (Not that I would.) Plus add the extra cost of TLC that tube amps require, and you are looking at about $300 every two years, or about $15/month. Is that $15 worth it to me? Absolutely, every penny!!
  8. Lovin Bass

    Lovin Bass

    Feb 8, 2002
    Los Angeles
    Thanks Lo-Z.

    I have finally come to the same realization. Am I more concerned with having a tone I love or should I save every penny I can and have an allright tone....Sacrifice!!!! I want the Tone!

    I love my Hughes & Kettner BassBase 400 and H&K BC410 cab but I would still like to have a tube amp as well but definetly NOT to replace the H&K.
  9. Yeah, you should get 18 months to 2 years out of power tubes in a properly maintained amp. Preamp tubes can (arguably) last the life of the amp. They certainly don't need to be changed as often. Proper maintenance/care includes what Lo-Z said, let 'em warm up before turning on the high voltage, 1-2 minutes should be plenty of time for the heaters to reach operating temperature. Letting them heat longer probably isn't necessary but it won't hurt. In older amps have a tube tech guy go through it and make sure that the electrolytic caps and bias resistors are all OK and not drifting. In an SVT you should check the bias once a week or basically every time you play it loud. It's easy to do, the test points with instructions are right under the front grill. All you need is a voltmeter and a small flat screwdriver. Keeping the bias correct is a key to long tube life in an SVT. Also, try to get very closely matched power tubes. This really helps. Any old set of 6550s won't do. Svetlana and Groove Tubes sell them matched. Probably some other companies, too. The SVT (and tube amps in general) is like a high performance sports car. If you don't maintain it properly you'll blow the motor! But the performance is worth the extra effort:D. IMHO, of course.

    Leopold: That could be a tube problem, but it sounds more like a bad cap or something. You should take it to a qualified tech and have him go through it to make sure everything is cool in there.
  10. BFunk

    BFunk Supporting Member

    Really? I have never heard that before. I am not disagreeing with you, it is not the "convential wisdom" that I am familiar with. Still, you have had this experience yourself.

    Yeah, I agree, I just think the amp sounds better after it has been running for 1/2 hr or so. The 1-2 minutes thing is the time it takes to safely heat the filaments.

    Not sure what of my post you are referencing. I am curious about it.

    Hmmm, didn't realize that this could be so damaging. I actually had a pre-amp tube do this. According to my tube-guy, this is very unusual. My brother had a power tube go bad on his guitar amp. Blew the tube socket out. I didn't realize that this could blow the output trans. That's some serious bucks to replace.
  11. With a properly maintained amp I can see tubes lasting for 20 or more years. especially some of the old US ones as PBG said. The 6550s I took out of my '76 were original Magnavoxes. They still work pretty good, but they're a bit microphonic. The amp wasn't used much, though, and certainly wasn't abused. The new tubes definitely sound better though. They only preamp tube I replaced was the 6C4, because it was severely microphonic. I replaced the splitter and drive tubes also (12DW7, 2x12BH7).
    I love my SVT!
  12. Rickenbackerman


    Apr 17, 2001
    Laurel MD
    My '72 SVT and '66 B-15 both have OG power tubes. I'm in 100% agreement with PBG.