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ampeg b25

Discussion in 'Amps and Cabs [BG]' started by Foster2004, Dec 8, 2004.

  1. Foster2004


    Sep 30, 2004
    Boonton, NJ
    I was given an Ampeg B25 and matching B25 cab (Both in great condition) I've seen some posts about the cabinet, and was curious if anyone knows the RMS handling and numuber of ohms it runs at. Any other info would be cool too, since I don't know much about it. I'd like to use it with my Mesa 400, bad/good idea?
  2. I have a minty mid 70's B-25B that is a sweet sounding head. I'm still looking for an original cab though. That head is 55 watts and the cab should be 16 ohms. As far as the wattage rating on the cab I'm not sure but my guess is that it wouldn't be a good match for your Mesa.

  3. BillyB_from_LZ

    BillyB_from_LZ Supporting Member

    Sep 7, 2000
    I believe that I've seen B25B cabinets with a 4 ohm/16 ohm switch on the back, near the input jack.
  4. NCorder

    NCorder Smoke-free since 4/3/05

    Dec 26, 2002
    Dayton, OH
    I have an Ampeg B25B cabinet from the 70's or early 80's. It has a 4 ohm-16ohm switch on the back thats now non-functional. A previous owner put new speakers in it, and didn't bother to wire it back up.
    I wish I had more specs on the cab for ya though. I'm curious about the RMS handling of the cab myself.
  5. BillyB_from_LZ

    BillyB_from_LZ Supporting Member

    Sep 7, 2000
    The RMS rating would probably be pretty dismal by today's standards. The voice coils in today's High power handling loudspeakers are made with materials that withstand very high temperatures. These materials simply weren't available in the '60s and '70s.
  6. Gary Broste

    Gary Broste

    Mar 21, 2008
    This is my first time on TalkBass (or any forum, for that matter). I'm a long time bass player and Ampeg user. I bought a new V4B in 1975 and have gigged with it an average of two nights a week ever since. I've banged it in and out of clubs during our twenty below zero winters up here in northern Minnesota. I finally had the amp gone through a few years ago. There was a hole burned through one of the tubes, but the amp was still working. What an amp! But it's a B25 that I have some questions about. I found the amp in a barn in about 1978. It had water damage and some of the Tolex and plywood had been eaten away by a porcupine! But the amp still works and sounds great. I found a name written on the amp just recently while rebuilding the cab. I was able to find the guy who said he bought the amp from a store in Minneapolis in the very early '70's. He said he didn't alter it at all. There are a couple of odd things about it. It has a built in speaker wire with a cannon plug on the end. The volume knobs are the new style ampeg knobs and all of the tone knobs are old style ampeg knobs. Are all B25s 16 ohms? Any thoughts? Gary Broste
  7. BillyB_from_LZ

    BillyB_from_LZ Supporting Member

    Sep 7, 2000
    Welcome to TalkBass...hide your credit card (this forum will give you G.A.S)!!!

    I believe the earliest SVTs used a 4 pin plug that would interrupt the plate circuit if the cabinet was unplugged so the output transformer wouldn't burn up. I don't know if they did that with any other amps.
  8. Gary Broste

    Gary Broste

    Mar 21, 2008
    Sorry about bragging on my amp, I'm unfamiliar. Thanks for the reply and info
  9. Loudthud


    Dec 25, 2007
    Dallas Texas
    Early versions of the B25 had the Cannon plug with the feature to save the output transformer if you forgot to plug it in. An extention speaker jack on the back of the amp had a mechanism to switch the transformer tap to 8 ohms when a plug was inserted. The B15 had the same setup. Later versions had two jacks on the back of the amp.
  10. Gary Broste

    Gary Broste

    Mar 21, 2008
    OK, I'm a pretty low-tech guy, I've been plugging this B25 into a single 15 inch 8 OHM JBL. Im I hurting it? What can I expect if I plug into a 16 OHM instead? Bigger sound?
  11. Mr. Watson

    Mr. Watson

    Mar 5, 2009
    I have a 1969 B25 head with the ampeg service manual. According to that,
    Power Handling: 130 watts RMS per cabinet
    Impendance: 4 or 16 ohms, selectable.

    hope that helps if you don't already know