Ampeg B25 Head, B15 Cab with Altec 421! Thx Craigslist

Discussion in 'Amps and Cabs [BG]' started by Smogcity, Mar 29, 2017.


  1. Smogcity

    Smogcity

    May 12, 2016
    Los Angeles
    I found a few odds and ends on Craigslist for almost nothing and I've been working on putting them together for a vintage live rig for the soul band I play with. I need to order a reproduction wheeled cart from Fliptops and dial in a few issues before i can gig it!
    >Ampeg b25 head..needs service: non working channel 1 and a slight buzz on channel 2
    >1964(?) orphaned very road worn B15 double baffle cab (no head) with original CTS speaker. The Cab buzzes at high volume..Need to figure that out..
    >Altec 421 that was pulled from a church sound system

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    Last edited: Mar 29, 2017
  2. Once you get the B25 working right, that should be a gret low power rig.
    I love the sound of those Altecs and it will help you get the most out of the watts you have.
     
    Smogcity likes this.
  3. Soulfinger

    Soulfinger

    Sep 20, 2004
    Houston, TX
    Cool looking rig. I think the question came up recently "what does a 421 sound like in a b15?", and no one had a particularly good answer---I guess you'll find out and report back. I've never measured, but the B15 cab and the B25B cab (where they used the 421) have to be about close in volume (per driver).
     
    Smogcity likes this.
  4. beans-on-toast

    beans-on-toast

    Aug 7, 2008
    I like a speaker that was only driven on Sunday.
     
  5. Reminder that the B25 should only be connected to a 16 ohm cabinet unless you engage the 8 ohm OT tap with the dummy plug or a second 8 ohm cabinet. I'm curious what the difference between the 421A and the 4218H is.
     
    Hoochie Coochie Man and Smogcity like this.
  6. Smogcity

    Smogcity

    May 12, 2016
    Los Angeles
    Thx for the reminder, yes I've got a dummy plug in it to run the one 8 ohm speaker!

    I've got the head into "Amphole" in burbank for repair (Bob Dixon runs it and is the best tube amp guy in LA)

    I spent a few days gluing down the loose bits of tolex all over the cab. It's still missing tolex in several places but I dig the authentic extreme road worn look. I glued all the interior seams and tightened down the baffle so hopefully the high volume rattle is delt with.

    Still waiting for the delivery from Fliptops with the reproduction cart and two additional handles (going to mount them on the side for easier loading.

    Question: The B-15's top board with the handle (that the the amp would normally mount onto) has no evidence of screw holes or mounting hardware...Could this have been an extension cab from birth in '64? Is that the significance for the model B-15-N L-XB (never seen "L-XB" before)
     
    Last edited: Apr 3, 2017
    bobyoung53 likes this.
  7. I'd ask you tech to make sure the speaker jacks are wired correctly. My B25B had both jacks connected to the 8 ohm tap when I got it.


    I have come across the model designation for the extension cabinet before but I have not retained that info. I believe you are correct. Wonder if @beans-on-toast could confirm.
     
  8. beans-on-toast

    beans-on-toast

    Aug 7, 2008
    Yes, Ampeg offered extension cabs for the B-15 N revisions. Some extension cab lids had the same fittings that the dolly had for attachment. The extension cab lid would screw into the bottom of the top cab, locking them together. It was more trouble than it was worth to couple the cabs together.

    Look for details in the TB portaflex wiki literature section. I can't recall what the part numbers were. L-XB is a Lansing speaker, extension, B-15NB cabinet. This is a double baffle, around 1963. The NC came out in early 64 but it wasn't unusual to be mated with a cab left over from 1963.
     
    Last edited: Oct 1, 2017
    bobyoung53 and Smogcity like this.
  9. Smogcity

    Smogcity

    May 12, 2016
    Los Angeles
    Cool thx for the info!!
     
  10. coreyfyfe

    coreyfyfe Supporting Member

    Nov 19, 2007
    boston, ma
    I just pulled the OT taps to separate jacks. You have to ditch the preamp send jack and move the second speaker connection there as the main speaker out cable hole is too close to the power tube socket to fit all three jacks.
     
    Smogcity likes this.
  11. I'm not following....why would you need more than the two ("speaker" and "ext. speaker") jacks?
     
    Smogcity likes this.
  12. coreyfyfe

    coreyfyfe Supporting Member

    Nov 19, 2007
    boston, ma
    I wired mine for separate 8 and 16 ohm jacks instead of doing the dummy plug switching trick.
     
    Smogcity likes this.
  13. Soulfinger

    Soulfinger

    Sep 20, 2004
    Houston, TX
    I keep coming back to this thread because the picture is just so cool.....this is the highest mojo rig I've seen in a while. The vintage P makes it.
     
    Smogcity likes this.
  14. Smogcity

    Smogcity

    May 12, 2016
    Los Angeles
    Thx!

    Even though the audience could care less if I showed up with a squire bass and line 6 amp, It gives me immense satisfaction keeping the old school vibe alive!
     
  15. Sure, makes sense, but why did you have to lose the pre-amp jack?
     
  16. coreyfyfe

    coreyfyfe Supporting Member

    Nov 19, 2007
    boston, ma
    The stock 16 ohm connection is the built in speaker wire. This is wired adjacent to a power tube socket with too little space between the chassis and socket to replace it with a speaker terminal. Without drilling additional holes in the chassis this means using the ext amp spot for the second speaker jack.
     
  17. Huh. Mine has simply two 1/4" speaker jacks in the "speaker" and "ext. speaker" locations. It's at my tech's right now, I'll check it out when I get it back. Curious.
     
  18. coreyfyfe

    coreyfyfe Supporting Member

    Nov 19, 2007
    boston, ma
    Might be able to get away with it if you position the speaker terminals perfectly and bend pins out of the way. It was too close for comfort for me. When I bought my B25 it was already converted to this setup, and I tried to rewire it with the preamp out attached (floating in the chassis it was picking up a ton of noise) but it didn't fit. Did the mod on a friends amp a few months later, same deal, but both are blue line models. It's possible things were spaced differently over time.

    Have some here but no good close ups on the jack wiring.
     
  19. beans-on-toast

    beans-on-toast

    Aug 7, 2008
    You also have to take into account the possibility of induced noise when wires carrying signals are too close to each other. Tube socket terminals too close to OPT output wires CAN have potential issues, even if you can bend the terminals away. It depends on the situation. There are reasons why signals are routed the way that they are in a chassis. It never hurts to try it and see of a mod works well.
     
    coreyfyfe likes this.
  20. Jim Carr

    Jim Carr Dr. Jim

    Jan 21, 2006
    Denton, TX or Kailua, HI
    fEARful Kool-Aid dispensing liberal academic card-carrying union member Musicians Local 72-147
    —by a church organist! :thumbsup:
     
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    Primary TB Assistant

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