Adding effects loop to AB763 circuit

Discussion in 'Shock Brother's DIY Amps' started by AAA71, Dec 12, 2017.

  1. AAA71

    AAA71 TDPRI Member

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    Has anyone added an effects loop to an AB763 circuit? I have been asked to do this but I am leery of it. It would be pre phase inverter, post reverb driver I would think.

    If anyone has any schematics of this idea I'd love to see them!

    Thanks guys!
     
  2. AAA71

    AAA71 TDPRI Member

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    No one has done this?
     
  3. Dacious

    Dacious Poster Extraordinaire

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    No-one sees the need probably. Changing the circuit, you'd have to probably buffer it both sides, which might adversely affect it. Maybe look at the Marshall Jubilee effects loop - for the other issues with this preamp, it's generally held to be a good neutral solution.
     
  4. AAA71

    AAA71 TDPRI Member

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    Basically I was asked to build a 64 Deluxe reverb. Which is not an issue. But I don’t really have any experience in effects loops - I’ve never had the need for one. I was just looking for tips. Thank you Dacious for your advice.
     
  5. D'tar

    D'tar Friend of Leo's

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  6. AAA71

    AAA71 TDPRI Member

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    Thank you D’tar. I’ve done loads of 5e3 mods but the ab763 circuit is so different I’m not sure whether to add the 5e3 mod there. Maybe rob rob will chime in.
     
  7. D'tar

    D'tar Friend of Leo's

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    Yea... I know its on the 5e3 mod page but it appears generic and easy enough to try. Maybe between the tonestack and volume pot?
     
  8. TooManyProjects

    TooManyProjects TDPRI Member

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    An effects loop in an AB763 might not accomplish much. Nearly all of the distortion in those amps occurs in the power amp, so there’s really no way to place a loop in any useful location. However, if you intend to boost the snot out of the front end and force the preamp to distort, you may want to consider running a parallel loop with the send and return in the same location as the reverb send and return. That way, you reduce the risk of altering the tone. The third preamp stage (the one after the reverb signal is recombined) will not distort in a stock DR because the signal is significanty attenuated by the reverb mixing resistors, so your loop will come after any distortion you may be able to squeeze out of the preamp.
     
  9. LoveChet

    LoveChet NEW MEMBER!

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    I have a circuit diagram for an effects loop that was added to a 1979 Silverface Deluxe Reverb. I made the diagram myself by chasing out the wiring. The mod was made by Paul Rivera California many many years ago. I had the mod made since I was chasing amp tone and the mod was suggested by Paul Yandel.
    Evidently he had the same mod made. To be honest I really don't know what he used in the loop. However I have successfully used a Stryman reverb in the loop since I dont't care for the on board spring reverb. As I have read, the things that go in a loop are delay type stuff as opposed to distortion.
     
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