Wednesday, 12 February 2014

Fender Eric Clapton 25db Mid Boost

Fender's take on trying to get EC's strat to sound like a Gibson. Some people seem to like it a lot, while others.. Not so much. But as i stumbled on a schematic, i thought this could work well as a pedal. With four transistors and not-so-simple design, there's little chance of fitting this onboard any guitar.. There are some non-standard values for the resistors, but as always, you should be fine with the closest ones you have. The layout doesn't have the magical TBX Tone control in it, but i've added another image that shows how to wire it up.






24 comments:

  1. If adding the TBX, any idea where you would connect the guitar input to the pot?

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    1. Input from the guitar to both, board and the TBX pot...
      +m

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  2. John, looks like it is wired just like a simple tone control....parallel (to ground) with the input.

    http://www.strat-talk.com/forum/353673-post4.html

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  3. I have a 1987 Fender Strat Plus with TBX tone control and it's pretty cool. I personally don't use tone controls ever but those who do should like it.

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  4. How hard is it to change this to the lower-gain boost from the Elite Strats and Teles? (This is supposed to be the evolution of the Elite preamp, which was a James Demeter design.)

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    Replies
    1. To reduce the gain to 12dB you must add a pair of resistors in the MDX pot.

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  5. Hi mirosol,
    First thing first: thanks for the layout. You and IvIark are doing an outstanding job, here. :)
    Now, I have searched for a schematic, for this, and all the ones I have found include a 330K or 332K resistor to ground, at the base of Q1, which your layout does not include.
    I have no idea, though, what this resistor is present for, so I'll let you advise whether it's important or not. :)
    The schematics I am referring to are the following ones:
    http://guitarwork.ru/electronic/Fender/Eric_Clapton_Strat_25dB_midbooster-preamp/
    http://www.blueguitar.org/new/schem/_gtr/ec_schem_fact.jpg
    http://i197.photobucket.com/albums/aa211/bajaman002/FenderEricClaptonActiveElectronics.jpg
    I'd love to give this one a go, and hopefully make it verified. :)
    Thanks
    Fred

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    1. Just FYI, when I tried to surf to the guitarwork.ru site my virus detection lit up like a Christmas tree.

      Just sayin'...

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  6. Mirosol, I have built this and it works. I had to use a 100K volume pot because the circuit oscillated with the 250K pot at the mid point of the rotation range. Works with all kind of transistors including germaniums.
    Thank you for another great layout
    Coi2001

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    Replies
    1. Strange thing with the pot value.. I'll tag it anyway. Cheers!
      +m

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    2. I think Frederic was correct about that missing resistor, so i added it to the layout. Updated now...
      +m

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    3. Hi, I made one too with Frederic's correction and as coi2001 I have a resonance and an oscillation when the volume pot is at 12 and when the mid pot is at max.
      The volume pot works as a master up to 12 and after it change the frequency response and the mid pot just increase the boost.
      I don't know how it supposed to work, but it's fun.

      Great layout !
      Fab

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  7. hi...is there a wiring diagram on how to connect the circuit to the guitar

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  8. hello. I'm trying to put this circuit together, and i have a couple of questions (i'm a beginner but i'm learning...)
    Can this circuit be used with both active and passive pickups?
    I assume that the wires 'Volume 1, Volume 2 and Volume 3' go to the connectors of the volume potentiometer. Same thing with the tone pot. But are you counting the pot connectors from the bottom or the top side?
    Thanks
    z.z.

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  9. Hi

    Initially, it was a dual preamp stage, the second one being an op amp.
    Both have a little tone correction.

    I am a French engineer and I have designed exactly the same preamp with a simpler design.
    It gives exactly the same result but is way simpler to achieve.

    Would you like me to post it?

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    1. This comment has been removed by the author.

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    2. Hi,Dominique! I'm ukrainian engineer and I'm interested at your discrette opamp schematic! Please send me a message to boxcustompedalsdoggmail.com

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  10. I'd love to share. But how do I upload the schematics?
    Dominique

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  11. upload to imgur ,then share the link?

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  12. Thanks for the circuit! I've just built it, and I have to unfortunately confirm it oscillates with 250K volume pot. Would there be any tip how to get rid of that - other than lowering the resistance of the pot? Many thanks!

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    Replies
    1. ... Just because I currently don't have a 100K pot handy... :)

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  13. OK, I've found out why the circuit might oscilate - all the "original" Fender schematics use only 50K(!) pot for the volume. I'll replace my 250K with 50K in my guitar during the week and will post the results here. Cheers!

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  14. I had the same problem - self-oscillation! - and it's true: after changing the volume pot to a 50k and putting the 250k to the mid boost knob everything works as expected! areyouexperienced.net also makes a note on this fact easily overlooked.

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