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tubes for Ampeg heads

Discussion in 'Amps and Cabs [BG]' started by naughtry, Mar 14, 2004.

  1. naughtry


    Jan 31, 2004
    NYC / D.C.
    So I just picked up a demo model SVT-2Pro from GC and I wondering about having back-up tubes on hand for gigs.

    Should I just carry a few extra power tubes or preamp tubes also?

    I'm curious to how often anyone has had tubes fail on them during a gig too?

    Also, wheres the best/cheapest place to order tubes from?
  2. Arthur U. Poon

    Arthur U. Poon

    Jan 30, 2004
    SLC, Utah -USA-
    Endorsing Artist: Mike Lull Custom Basses
    I used to carry a pair of 6550 power tubes and 2 12ax7's and 2 12au7's for the preamp section just in case of failure. Although many of the posts I've read about preamp tube failures being very low, I carried extra preamp tubes just in case. The reason I carried 2 6550 power tubes was that the manual stated if the unit had a power tube fail, it was best to change them in pairs. But I'm not sure if this is true. PsychoBass Guy is the man when it comes to info on tube amps, hopefully he'll post an answer to your thread. I no longer have an SVT, but I did have a power tube fail, luckily during a practice session. For low prices on good tubes I'd check out lord valve's website.

    I hope this helps, A.P.
  3. JonB


    May 27, 2003
    I've never had a tube fail on a gig, but did carry spares just in case. Once we had a power surge which took out 2 protection fuses on my V4. Played the rest of the gig with 2 6L6's out, and never missed them! Another time, a roadie dropped my B1 off a stage, which jolted a tube out of it's socket - those are my only horror stories.
    Probably the power tubes are more likely to fail then the small signal tubes like 12ax7's.
    You can buy tubes from Tube Store and order them matched, that way you could order one extra with the same rating so that you don't have to carry matched pairs.
  4. naughtry


    Jan 31, 2004
    NYC / D.C.
    Thanks for the help, I just have a few more questions for anyone.

    Would the 6550-WE Sovtek be a direct replacement if I wanted to just replace a pair if I get a blown power tube?

    If I was to blow a tube would it be about time to replace them all anyways?

    I found some really good prices for 6550-WE Sovtek Matched sets here at Triode Electronics. Is that what I should go for or the SED 6550C's?
  5. You don't need, nor should you carry replacement power tubes. If you lose a power tube on a gig, swapping it out without bias adjustments, even if it is supposed to be "matched," can do far more damage to your amp than waiting for a qualified tech to replace them. Tubes do NOT just up and blow, and if one dies, 99% of the time, there's something wrong with the amp to cause it.
  6. Jerrold Tiers

    Jerrold Tiers

    Nov 14, 2003
    St Louis
    I would agree.

    Power tubes fail catastrophically when there is a problem. Otherwise they gradually get "soft" as they age and the emission material on the cathodes degrades.

    If one does "fail", the replacement will quite likely also fail, for the same reason. Expensive, and not helpful.

    Preamp tubes are easier, if you don't mind diddling with the amp at the gig trying to figure out which one is bad. Not the best place for repairs, usually.

    And preamp tubes don't usually "fail" either. Not much in the amp can kill them, either, unlike power tubes. They may get noisy, but usually anything they do builds up over time so you have a chance to get it fixed way before its dead.

    Best solution is to have a backup amp, like your old/practice head in the car as a spare, etc. Drag it in and swap.

    Easy, quick, does not require mentally shifting gears, and doesn't delay the gig much. Hopefully its a smaller and lighter unit............

    Or, don't sweat it. When was the last time your amp died? And if it did, was it something you could have fixed right there?
  7. nysbob


    Sep 14, 2003
    Cincinnati OH
    Quick swapping of tubes on a gig is risky at best...I carry a boat anchor old SS sunn coliseum for backup of my tube SVT on tour. Never had to use it. I've been using tube amps for the past 20 years and the only problem I EVER had was a power tube arc on my Marshall 100W...that was back in '87. ;)
  8. naughtry


    Jan 31, 2004
    NYC / D.C.
    This is my first tube amp and I have always heard stories about tube amps being unreliable so I just wanted to be prepared. I remember the guitarist in my old band was always carrying extra tubes everywhere, thought it was something I shoud be doing. I have a old peavey Mark III head lying around that would be a good back-up I guess. Thanks.
  9. Don't believe the stories and besides, I'd never accuse many guitar players of being guilty of behavior I'd want to emulate. ;)
  10. naughtry


    Jan 31, 2004
    NYC / D.C.
    hehe... he even left some tubes in the back of my car 3 years ago that hear ebay calling there name considering I havent seen him since. :)

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