Converting tube PA amps to guitar/bass amps

Discussion in 'Amps and Cabs' started by El Jefe, Oct 19, 2008.

  1. El Jefe

    El Jefe Member

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    I just picked up a couple amps for $100 on craigslist. The first is a Knight KN3050a. It's a 2xEL34 amp, tube rectified, with three 12AX7's in the preamp. I'm thinking of doing a 5F6a preamp and lowering the negative feedback, I don't really think it's going to need much more than that (other than changing the I/O to 1/4")

    The other one is a Bogen M120. I read that this used 8417 output tubes - those are out of the question. I would really like to convert this into a bass amp. I'm pretty sure it can be modded to use 6550's or KT88's, but I'm a total novice with electronics - itching to learn though! What are the pros and cons of the various tubes? What kind of power can I expect to get out of it? Any particular things I should do to make it sound good for bass guitar? I'd like it to have just a volume, treble, and bass knob. I don't need any other controls. Here's a pic of the chassis:

    [​IMG]
     
  2. El Jefe

    El Jefe Member

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    Bump


    Aren't there any techs here?
     
  3. JBarlow

    JBarlow Member

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    With all due respect, you might try posting this in the "Amp Technical Forum" area. Lot's of great minds here. I'm sure you'll get something.

    --Jason
     
  4. SatelliteAmps

    SatelliteAmps Member

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    JBarlow is correct. Could you be a bit more specific as to what you are looking for? The Knight will need a bit more than just adjusting the negative feedback and the preamp section.

    The Bogen can be converted to run 6550's or KT88's. They all fit in the same style of sockets. If you are going to convert it to a bass amp, it might be easier to just gut it and rebuild from scratch, rather than fighting to overcome the limitations of using an old Bogen as a bass amp.
     
  5. AdamGian

    AdamGian Member

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  6. doctorx

    doctorx Member

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  7. El Jefe

    El Jefe Member

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    Thanks, I didn't realize there was a separate forum for that.


    I don't have schematics for the Bogen, but I found a guy who has one and said to email him for it.


    I want to make the Knight into a simple guitar amp - 2xEL34 with just master, bass, treble. Same goes for the Bogen except I want it to be 4x6550 and be tuned for bass. I suppose I might not mind having a master volume on the Knight if it's not too much trouble.
     

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