FX loop alternative

To the left is the previously posted alternative loop modification schematic to change a Mesa Dual Rectifier from a parallel loop to a serial loop.  It’s easy.  Most of the time required for the mod is spent taking the amp apart.  (Here’s a link to a 2 Channel Recto with the same mod.)

The following pictures are provided to show the inside of the amp, the job, and a crappy job someone did of soldering the output transformer to the daughter board.  I used a 22 gauge wire with the insulation removed for a clean, short jumper.  I’ve seen people use insulation for the job, but the space is tiny.  Note that my solder joints look a little matte.  This is from the lead-free, silver solder I used.  Almost every joint looks that way when I use it, no matter what, but it hasn’t been a problem.

Update July 2016: Verified.

Before any work.

Before any work.

Side shot before any changes.

Side shot before any changes.

Jumpered.

Jumpered.

Jumpered, side view.

Jumpered, side view.

Taped off the wires.

Taped off the wires.

Someone did an ugly, poor job on the OT.

Someone did an ugly, poor job on the OT.

Funky!

Funky!

Ah, the lovely glow.

Ah, the lovely glow.

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Comments
  1. Russell says:

    Looking into this for my ’02, 3 channel DR. Thanks for posting this! Does this particular mod retain the ability to engage/disengage the modded effects loop from the footswitch, for all channels? Your article reads that way, but it isn’t 100% clear to me. I realize that the ability to program effects loop per channel is lost, which is fine. I am just asking from a global perspective.

    Thanks again!

    Like

  2. Chad says:

    Seemed to work on triple rec. Still get signal when there isn’t anything in loop though. It’s weak but if I turn it up it’s bedroom volume? Is that normal? Otherwise I been using 4cm with my Helix no problem.

    Like

  3. ben says:

    Hi,
    I want to do the mod, but i hace a question.
    What do you to with de wires before tapped them, do you join them?

    Like

  4. JB says:

    Oh! Hello!! I’m about to start modding my 3ch DR. And the first thing I want to try is this para loop jump! You think this will bring more “tightness” to it afterwards, like for metal-ish modern gainy stuff? I mean I love it’s fluffyness but recently got another amp for that :3

    And about these mods, have you had any experience on the so called “pre500” mod? Will it be worth the hassle?

    Thank you in advance mate,

    JB

    Like

    • Warpedpig#1 says:

      I haven’t performed other mods. This mod removed a phase issue I was experiencing which made it sound hollow. Since then I’ve been pretty happy with the tone. The amp will always sound better with the loop bypassed, but now having the loop engaged sounds a lot closer to the bypassed sound.

      As far as the pre-500 mods: a big component of those models was the transformers. That’s not going to be possible to obtain, unless you buy a dead Mark IV. You might consider a Mercury Magnetic OT upgrade, but that’s very expensive, but it may be worth the money to have the additional mass of iron.

      I’ve read several threads on The Boogie Board referencing jumping of the 100 ohm cathode resistors. It increases available gain and people haven’t gone back to stock.

      I seem to remember the Gain pot being changed to 1 Meg. I don’t think that’s necessary.

      Like

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