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6550's in a B-15

Discussion in 'Amps and Cabs [BG]' started by sedan_dad, Mar 27, 2009.


  1. sedan_dad

    sedan_dad Supporting Member

    Feb 5, 2006
    Columbus,Ohio
    Jess Oliver was quoated as saying;

    "I've found that the new Sovtek 7027A tubes are great. If you can afford to replace the 7027A's with 6550 tubes so much the better. Unfortunately, I didn't leave enough room between the tube sockets on my Oliver brand amps to fit 6550's, which have bigger glass bottles."

    Has this been discussed?
     
  2. Chinguschild

    Chinguschild

    Apr 17, 2006
    Chico, Cali
    Where's Jimmy M when you need him.
     
  3. coreyfyfe

    coreyfyfe Supporting Member

    Nov 19, 2007
    boston, ma
    Probably similar to the V4. I run my V4 with 6550s in the place of 7027s, so I would assume a B15S would work to a similar end. It was a pretty quick mod, just a few resistors and such.
     
  4. JimmyM

    JimmyM Supporting Member

    Apr 11, 2005
    Apopka, FL
    Endorsing: Ampeg Amps, EMG Pickups
    Looking for someone who can answer. I'm an "If it ain't broke, don't fix it" type.
     
  5. Chinguschild

    Chinguschild

    Apr 17, 2006
    Chico, Cali
    Well then. Problem solved.
     
  6. FenderP

    FenderP Supporting Member

    May 7, 2005
    This would be for the B-18 or the B-15S (the later one) both of which had the 7027A (same as the B-25B head) ... not the B-15N.

    When the 7027As were hard to find, a lot of people modded 7027A tube sockets to take 6550s. I like the 7027A in my B-25B so I kept it all original.
     
  7. Just IME/IMO the 6550 are louder (I almost hate saying anything with the letters l-o-u-d in it) but the 7027's had a slightly better sound even though they break up sooner and had a shorter life. The life problem may no longer be an issue with new manufacture?
     
  8. FenderP

    FenderP Supporting Member

    May 7, 2005
    My 7027As last years. Don't know what others are doing to them :)
     
  9. JimmyM

    JimmyM Supporting Member

    Apr 11, 2005
    Apopka, FL
    Endorsing: Ampeg Amps, EMG Pickups
    My V4B lasted for over 15 years with the same tubes.
     
  10. Maybe it was just "Groove Tubes" that went soft? I couldn't pop for NOS before they dryed up. Lost bottom end on two sets from GT in about two to three years each. Don't bother asking about bias, checked/adjusted if needed every 100 to 200 hours. The GT's did drift more than I would have liked but no wild changes.
     
  11. JimmyM

    JimmyM Supporting Member

    Apr 11, 2005
    Apopka, FL
    Endorsing: Ampeg Amps, EMG Pickups
    I could believe that about GT's. Tubes really did suck for a good long time when production first went to the third world. Mine was loaded with the original Sylvanias ;)

    Damn, do I miss that amp. I bought it and an 810 from my cousin's husband for $500 in 78. I used that sucker for everything from metal to top 40 and it always kicked ass. A bar fire took it out.

    I WILL have another one...one day...probably not any time soon ;)
     
  12. FenderP

    FenderP Supporting Member

    May 7, 2005
    I actually own the matching 2x15" for the B-25B. It was the same one I used back in high school - bought it from them. They no longer had the head, but I found the right matching vintage one and I'm all set :)
     
  13. They were not being produced at that time, trouble is with GT you don't know who they re-branded? They were not Sylvania or RCA, looked like GE's. I heard a rumor so I can't say with certainty that GE was shipping standard 6L6GC's with 7027A on the glass.
     
  14. sedan_dad

    sedan_dad Supporting Member

    Feb 5, 2006
    Columbus,Ohio
    I thought that 6550's were just higher powered versions of 6L6s.
     
  15. beans-on-toast

    beans-on-toast Supporting Member

    Aug 7, 2008
    Here is some useful info on the 7027A /6L6 /6550 related to Ampegs http://www.triodeel.com/7027.htm
     
  16. zagnut

    zagnut

    Jan 4, 2009
    Back in Detroit
    That sucks! The fire start when you were there? I would have had my axe under one arm and the head under the other running for the door.

    Tis a shame you didn't see any kind of reimbursement for it from the bars insurance claim.:scowl:
     
  17. JimmyM

    JimmyM Supporting Member

    Apr 11, 2005
    Apopka, FL
    Endorsing: Ampeg Amps, EMG Pickups
    Ya, no doubt! I tried...got nothing.

    The fire happened while I wasn't there, though. It was a 2-week 4-night gig, and it happened on the Sunday afternoon after our first week. I forget the circumstances, but it wasn't ruled arson. But it taught me. From now on, my stuff goes with me on days off!
     
  18. pgk

    pgk

    Aug 19, 2007
    Unfortunately, I didn't leave enough room between the tube sockets on my Oliver brand amps to fit 6550's, which have bigger glass bottles."

    yep sadly that's true; i own an Oliver B200 head. i talked to mr oliver about it, to more or less ask him for his blessing to move the sockets a little further apart! i think he kinda got a kick out of it and said sure go right ahead. he was amused for sure. but i'm not going to; when i have it restored it'll sport a pair of JJ big bottle 6L6's, and it will sit atop an ampeg bt15 cab. that's interesting from a historical perspective; the bt15 was the first ss B15, and those amps are what drove mr oliver away from ampeg and he then started building his own line of amps. pretty cool if you ask me....

    hmm, maybe jimmy'd start a separate "bastard stepchildren" section of this thread?!? if so then gimme a number!

    as far as 6550's in a B15 goes yes it can be done; the trannies will supply enough heater current and they will fit. some bias supply mods are probably in order too. i think you'd have to go with a ss rectifier, although i could be wrong about that one. i have a friend in kansas city who did that very thing with his B and it is killer. not so much louder as it is fuller and fatter, with a bit more headroom before breakup. different than the classic B tone but very cool nonetheless. i think a pair of 6550's in the higher powered/larger cab B15S would Rule. done correctly you won't hurt a thing.
     
  19. JimmyM

    JimmyM Supporting Member

    Apr 11, 2005
    Apopka, FL
    Endorsing: Ampeg Amps, EMG Pickups
    pgk, it says very clearly on the first post of the original Portaflex Club thread that anyone with an Oliver gets in, but you have to post it in the actual Portaflex Club thread ;) I'll go ahead and add you, though. Just take a couple pics, please!

    BTW, on the first page of that thread, Mark from Vintage Blue posted some extremely detailed pics of his Oliver Powerflex. You should check it sometime. Amazing looking amp. I love the motor that raises and lowers the head!
     
  20. I'm not so sure this is true. Each pair of 6550 is going to require getting on for one and half amps more in heater current. That's an added load of about 9VA the power transformer has to supply over what it was designed for. It will run hotter and have a shorter life. The PT in my B15 certainly runs warm enough already.

    Paul
     

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