Request: Way Huge Fat Sandwich

FatSandwichI’m checking in today posting a layout for just another dirt box. This one, however, seemed a bit more interesting than your average tube screamer; or at least the schematic did. I’m not sure how this thing is going to sound, but hopefully it’ll work at least. There are a few unknowns, specifically the MOSFET and the clipping diodes, but I’m guessing these can be common substitutes for the most part.

The layout is based on a schematic from this forum thread.

Update (18.02.2014): Now verified as working, thanks to Freppo!

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5 thoughts on “Request: Way Huge Fat Sandwich

  1. Hi Harald. Hope all is well. Do you know where I could find a data sheet on the JRC7031D? I want to compare it’s pin out with the TL071.

  2. You should tag this one as verified! 🙂

    My build is very noisy (sounds like hiss) but other then that it works and sounds great. I will order a couple of 2N2484 transistors and see if that helps with the noise. The tone and part of the circuit reminds me alot of Emma Reezafratzitz, and my build of that pedal is noisy aswell..

    I’ve played around with the controls alittle more and forget what I wrote earlier…

    These are my new observations:
    The drive pot is kinda useful as it effects the bass-response as well. A logorythmic pot works best there is you wanna put the drive outside the box.

    The high pot is suble, so I would make that a trimmer.. but tone, curve, presence and res are all useful pots. The action of the res pot is strange as I mentioned before.. not much happening except at the beginning and end of the rotation. At one side is gets thin, and the other side it gets muffled.. so I kinda acts like another tone control. I will try different values there to see if I can get a better more useful sweep.

    Cheers
    / Freppo

  3. Hi Harald

    I built this one with sucess! 😀

    The controls works perfectly and it has a great tone, but it’s very hissy/noisy. I will try different transistors tomorrow and see if that help with the noise. I used 2n2222a’s for Q2/Q3, a BS170 for Q1 and a TLE0271 for IC2.

    The drive pot isn’t very useful imo.. it only starts to sounds crappy as you turn it up (maybe it’s useful if switching from guitars with humbuckers to singlecoils), but i would leave that as a trimpot or even place a fixed resistor insted.

    The Res pot is a bit weird, it doesn’t do much at all most of the turn but at both extremes it thins out and looses all bass. Not very useful imo.. I would just leave it in the middle position at all times.

    The curve pot is very useful though, it softens the gain and attenuate any “fizzyness” without cutting to much treble. The presence and tone pots also works fine, even if they sort of do the same thing. I can see why the presence pot is a trimmer in the original.

    Thanks you for yet another great layout!
    cheers / Freppo

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