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Thursday, December 5, 2019

Discrete Distortion +

I've seen a few people playing around with discrete opamps in classic circuits, and thought I'd give it a go with one of my favorite circuits, the classic MXR Distortion + (or DOD 250, etc.). The typical 741 opamp has been replaced with Joe Davisson's Diode-Compression Opamp. The 6.8k resistor in the bottom left corner of the board may need to be adjusted till the collector of Q3 is around 4.5v. I haven't tested this, but it should work.

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7 comments:

  1. CrossoundDecember 5, 2019 at 6:13 PM

    que interesante¡¡, ¿tienes idea si es posible reemplazar los 2n5087 por BC557 o 2n3906?, ¿la ganancia del transistor debe ser superior a 200hfe? gracias por subir el aporte, hace tiempo buscaba algo así.

    ReplyDelete
  2. Diego JorgeDecember 6, 2019 at 11:01 AM

    Wampler mods for this? :3

    ReplyDelete
  3. Marcus CorradiniDecember 12, 2019 at 12:52 AM

    Verified!

    ReplyDelete
  4. Marcus CorradiniDecember 12, 2019 at 8:45 AM

    With germanium diodes the tone is great, but the volume is a little low. With 4148 the volume is much louder, but the tone is not so cool. Any suggestion? When I set the 6k8 resistor to 4.5V on the Q3 collector, the gain pot stopped working. With 6k8 everything worked normally. Great layout, as always! Thank you!

    ReplyDelete
    Replies
    1. Effects LayoutsDecember 12, 2019 at 9:15 AM

      There are several things you could do. Start here:

      https://www.diystompboxes.com/cnews/mods.html

      Delete
    2. Erald. YOctober 21, 2022 at 8:27 PM

      That link was incredible. Can't believe I didn't run into it earlier. Thanks a lot for everything you do here.

      Delete