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Not sure what to do with this

Discussion in 'Amp Tech Center' started by JSMac, Jan 12, 2021.

  1. JSMac

    JSMac Tele-Holic

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    Hey folks.


    Can you see any guitar amp potential for this old audio amp.

    I converted a pair of these for use as audio mono blocks. In the process I removed the first preamp section and tone and volume controls. I'd like to keep the build as simple as possible.

    Thanks!

    Edit: Looks like a need to try to find a way to attach a larger schematic.
    6At6, 12AU7, 6BQ5 x 2, 5y3.

    upload_2021-1-12_11-12-38.jpeg
     
  2. JSMac

    JSMac Tele-Holic

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    ..
     
  3. uriah1

    uriah1 Telefied Gold Supporter

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    Looks like some early Gibson types.
     
  4. Peegoo

    Peegoo Poster Extraordinaire

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    If it's a monoblock config right now, pretty much all you need is a tone section voiced for guitar and a 1/4" jack. Consider a Vox AC-15 or similar to serve as a guide.
     
  5. JSMac

    JSMac Tele-Holic

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    I plugged a guitar in and the output is very low. Maybe I could put the first preamp tube back in the circuit.
     
  6. timfred

    timfred Tele-Meister

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    It has all the components for a 5E3-ish something. It looks like it depended on a pre-amp for volume control. What *I* would do:
    1) swap in 6AV6 for 6AT6
    2) implement basic 5e3 tone+volume control instead of the tone-bass stack there currently
    3) see how it sounds. stop here if happy.
    4) swap in 12AX7 for 12AU7
    5) change plate resistor on first 1/2 12AX7 to 100K
    6) rewire second 1/2 12AX7 to be a standard cathodyne phase inverter
     
  7. jvin248

    jvin248 Doctor of Teleocity

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    .

    Check out these two channels for radio conversions. I grabbed the first couple of videos so they may not be representative of what you need but they are the breadcrumbs back to more similar content.




    .
     
  8. JSMac

    JSMac Tele-Holic

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    Cool. I have a Hammond AO-35 waiting to be converted. With all of the possibilities I need to decide what to do with it.
     
    Last edited: Jan 18, 2021
  9. JSMac

    JSMac Tele-Holic

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    I'm looking at the 1960 Vox AC15 schematic and that might work. It calls for an EF86 for the first preamp tube. Should I stick with that or can/should I wire it for something else like a 12AU7? It looks like the newer models use all 12AX7s.
     
    Last edited: Jan 28, 2021
  10. DucDone

    DucDone Tele-Meister

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    You should try EF86. I am just finishing my build, and the EF86 tube sounds quite nice.
     
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