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question to ampeg v4b owner please

Discussion in 'Amps and Cabs [BG]' started by bouncy, Sep 25, 2017.

  1. bouncy


    Sep 25, 2017
    Sorry for double posting. I am a new member, posted once over the "new member" side.
    I am 56, just start playing, no big dream, for fun only.

    I bought a set of minty 1974 v4b with V6-b cab on the weekend from a 71 yrs old musician. He already updated the filter cap with F&T cap, a new set of JJ 6l6, preamp tubes are original. He told me 6l6 will work just fine. I am not after the big sound, should I switch it back to 7027a? what is your thought?

  2. JimmyM


    Apr 11, 2005
    Apopka, FL
    Endorsing: Ampeg Amps, EMG Pickups
    7027a's are really 6L6GC's with a different pinout. At least that's what they are these days, and from what I'm told, old ones are more alike than different. I don't know...I liked my old V4B with 7027's, I like my new one with 6L6's. I could go either way, but you definitely have more choices with 6L6's.
  3. coreyfyfe

    coreyfyfe Supporting Member

    Nov 19, 2007
    boston, ma
    Essentially, a few internal pin connections (5-6 and 1-4) and higher power handling in the 7027A versus 6L6GC. Not exact matches, but close enough in the right circumstances. People run 6L6GC in vintage V4/B amps, I like to stick to 7027A but I've not had good luck with new production and NOS get expensive.

    As you mentioned, new production tubes are generally regarded as just a 6L6GC with the extra connections. The JJ datasheets available for their 7027A are listed with 500V power handling, 100V shy of NOS 7027A. I have sovtek boxes that say 7027A but they aren't listed on the new sensor website.

    I'd say if the amp was checked by a tech, biased appropriately, and seems stable, then it's fine. Keep an eye on the tubes, if the amp suddenly makes weird noises and a tube is glowing like a tomato shut it down. If it sounds good and stays stable it's probably fine.

    Another alternative is the new sensor tung sol 7581A reissues. I've heard good things from a few people using these in their V and B series ampegs and I think @beans-on-toast has been using them in his V4. Similar story, they're close enough to a 6L6GC in these amps to be run as a replacement.
    JimmyM likes this.
  4. beans-on-toast

    beans-on-toast Supporting Member

    Aug 7, 2008
    Yes the reissue Tung-Sol 7581A is plug in compatible with the 7027A and works well in my vintage V4B. I did rebias it.

    You can run a 6550 in the V4B. Ampeg offered this as an option.

    But good news, Tung-Sol is now offering a reissue 7027A. If it is anything like the 7581A, it’s worth a try.

    www.thetubestore.com - Tung-Sol 7027A Audio Tubes.

    With the higher plate voltages in the V4, a 6L6GC will work but it will not have a very long service life in comparison to a 7027A, etc.
  5. coreyfyfe

    coreyfyfe Supporting Member

    Nov 19, 2007
    boston, ma
    I hadn't seen these yet. Might be worth a try, I've liked most of the tung sol reissue stuff that new sensor has been putting out.
    beans-on-toast likes this.
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