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question about ohms with Ampeg b25b...

Discussion in 'Amps [BG]' started by twotonetommy4, Nov 18, 2012.

  1. twotonetommy4

    twotonetommy4

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    Hey guys,

    So i realize there is most likely multiple forums explaining what I am trying to figure out...but I was hoping someone could help since I truly know nothing about ohm ratings and what head is good to match with what cab.

    I've recently purchased a 1969 Ampeg b25b head off a guy from Craigslist, and have now noticed the head says "16 ohms" near the speaker output. The cabinet I own is the Ampeg 4x10 HLF classic.

    My question is, will this combo work? i have yet to try it out because I a do not want to mess anything up in the head or speakers. If the combo won't work, what do I need to do to make it work?

    Thanks for any and all help. Hopefully there is someone out there willing to teach me a lesson about ohms and compatibility between amps and cabinets...Shed some light on this poor soul!

    Thanks guys....
  2. Roadkill

    Roadkill Short Scale Addict Supporting Member

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    That amp requires a 16 ohm cab - just like it says. The cab you have is 4 ohms but could be rewired to 16 if you don't need the horn. You can also "fool" the amp into driving an 8 ohm cab by plugging a dummy plug (no cable connected) into the second output jack. What are you planning to do with it? It really doesn't have enough power to play with a rock band.

    I have one of the 2x15 B25 cabs but haven't found a head for it yet - I'd only use it at home anyways. My cab has been rewired to 4 ohms but could be wired back to 16 if I ever have need. Sounds great with the '67 Bassman I have :D .
  3. One Drop

    One Drop Supporting Member

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    Also check the sticky here at the top if the page. All you need to know and more.
  4. twotonetommy4

    twotonetommy4

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    Roadkill...so by dummy jacking to make it think it is running 8 ohms will be okay for my 4 ohm cabinet?

    And I've lots of reviews with people saying the b25b is their main gigging amp, plenty loud enough for all smaller-midsize gigs and rehearsals, which is I all intend on using it for.

    thanks for your help sir!
  5. Roadkill

    Roadkill Short Scale Addict Supporting Member

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    No - but since 16 ohm bass cabs are extremely uncommon you could then run an 8 ohm one. As I said you could rewire your 4 ohm 4x10 to 16 ohms but you'd have to know what you're doing - not something someone can explain over the web :( .
  6. One Drop

    One Drop Supporting Member

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  7. RickenBoogie

    RickenBoogie

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    +1 the 4 ohm cab can be re-wired to 16 ohms, which would then be a perfect match for the amp. Tube amps should always be run with a load that matches the ouput. Some amps have a swithable ouitput for 2, 4, 8 ohms, etc. Yours will do 16, or 8. You have a 4 ohm cab, so rer-wire for 16 ohms and you're good to go. Do not run it as is @ 4 ohms.
  8. twotonetommy4

    twotonetommy4

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    thanks Rickenboogie...I guess my next question is...how do I rewire to 16 ohms, and will doing this compromise volume levels? Guess I could take it into the music shop, but trying to save $$$ if I can.

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