Mod'ing the Tone Monk Seed of Life Fat Switch

Discussion in 'Effects, Pedals, Strings & Things' started by MarkF786, Jan 25, 2012.

  1. MarkF786

    MarkF786 Member

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    Since my quest to determine the SOL schematic was based on the soul purpose of fixing the "fat" switch so it wasn't "obese", now that I see the schematic, I see it's an easy fix even if the pedal is gooped.

    First, to understand how the fat switch works, please read this article by Jack Orman: http://www.muzique.com/lab/fatt.htm. On the SOL, the SPST is doing the the exact thing as in the second-to-last diagram; in the "fat" mode, the switch bypasses the .047uf capacitor.

    Keep in mind that when putting capacitors in parallel, you add their capacitance, so instead of bypassing the capacitor and adding maximum fatness, you can just increase the capacitance by putting another cap in parallel to achieve the degree of fatness you desire.

    Instead of using the SPST switch, you can replace it with either an "on-on" SPDT switch with one leg being disconnected and the other leg being connected to a capacitor in parallel (this would allow you to select between the default .047uf or .047uf + whatever capacitor you put in parallel) or you could replace it with an "on-off-on" switch to allow you to select between either the default .047uf or .047uf + two different additional capacitors in parallel. For a good example of this, see the "Mids" switch in the schematic for the BYOC OD2: http://buildyourownclone.com/overdrive2instructions.pdf.

    To give some comparative values, the Rockbox Boiling Point switches between two settings: the stock .047uf or .22uf. To achieve similar results, you'd need to use an "on-on" SPDT switch and a .15uf capacitor.

    Or on the BYOC OD, they use a "on-off-on" SPDT switch to choose between three different total values - .047uf, .094uf, or .197uf (using an additional .047uf or .15uf capacitor in parallel). I find the .047uf in parallel to have a minimal effect, so I'm planning to go with .15uf and .22uf capacitors.

    I've done some preliminary testing tonight just using jumper cables, and it seems to work well. This weekend I'll solder in the new switch and capacitors.

    If there are any technical inaccuracy, feel free to correct me.
     
  2. Hulakatt

    Hulakatt Supporting Member

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    sounds solid to me, others have been wondering about this as well
     
  3. Whalestone

    Whalestone Member

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    According to the schematic I've seen, the Rockbox Boiling Point switches between .22uF and .47uF, not .047uF.
    Having more gain than a TS a la the LDO, the .22uF setting achieves a TS style hpf of -3dB @ .7kHz.
     
  4. MarkF786

    MarkF786 Member

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    Yes, you are correct; at first I thought it a typo but now I realize that the resistor in the RC circuit also changes value from 4.7k to 1K, which the LDO (and apparently the SOL) does.

    So in the stock circuit with a .047uF cap and a 4.7K resistor, the corner frequency is 720Hz. In the BP/LDO/(SOL?) circuit with a .22uF cap and 1k resistor, the corner frequency is 723Hz (not much difference). If you increase it to .47uF, you drop it to 339Hz. It seems then jumping to even higher values like 1.0uF would have a more pronounced effect, with a corner frequency of 159Hz.

    The basic principle remains the same though - rather than bypassing the cap, add another one in parallel to decrease the corner frequency of the filter. I'm going to do more experimentation with values this weekend to see what sounds best to my ears.

    I was thinking last night as I fell asleep, I might use an SPDT "on-off-on" switch and wire it so I have a capacitor on one leg (.47uf? 1.0uf?) and have the other leg bypass the cap on board, which would allow me to select between the stock SOL "fat" boost, the standard response, and the new "fat" boost.
     
  5. Ed Reed

    Ed Reed Senior Member

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    [​IMG]

    I just addd this and it works! Sounds much better! The red dot version has arrived! (joke)
     
  6. MarkF786

    MarkF786 Member

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    Here's my mod'ed SOL "fat" boost. I ended up going with a .22uF (adding up to .44uF, close to the bass boost on the Boiling Point) and a 1.0uF for a bigger bass boost. So with the three way toggle, the up is a small bass boost, middle is stock, and down is a large bass boost (almost as fat as a triangle muff). I had to use what I had on hand, a film cap for the smaller value and a electrolytic for the larger valuer.

    The pedal sounds so much better now, IMHO. With the large bass boost (that doesn't fart out like stock "fat" boost), it sounds like a different pedal, allowing you to get that heavy, low-end distortion almost like a muff or rat.

    [​IMG]
     
  7. Ed Reed

    Ed Reed Senior Member

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    As I said If I had a clue what I was doing and I don't. Wonder why my results turned out like they did? My mod is probably a joke but it works and sounds far better than the original. I need to get some caps of the right value and try yours. If it sounds better than mine it's got to be the best sounding sol out there. I wonder if Ken will start adding this to his, that is if Ken ever sells another pedal.
     
  8. MarkF786

    MarkF786 Member

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    It was such a simple mod, I can't believe that Ken didn't do something like this already. When I emailed him in July about changing the "fat" switch he replied, "A rework of the SOL circuit has been in the works since December, and we are hoping to release it in the winter. I know that seems long, but it's not an overnight process."
     
  9. Ed Reed

    Ed Reed Senior Member

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    I'll try to get a clip or two of mine up in a day or two. Care to make some of your mod? Might be an easy way to tell how they compare?
     
  10. Ed Reed

    Ed Reed Senior Member

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    Just finished building a GGG screamer with the boutique mods. I added the cap only (.047) and it did boost the lows but very little. I then added my resistor across it (2.2K) and it opens the pedal up with a nice full low end but not mushy at all.
     
    Last edited: Jan 28, 2012
  11. Heady Jam Fan

    Heady Jam Fan Member

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    This reminds me of when I mod'ed my Alpha.
     
  12. Rocksully

    Rocksully Member

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    I have one of the early SOL, and I've always ran it before my Tim in my signal chain. The Tim is an always on pedal for me. I've never thought the SOL sounded bad, but perhaps because it was always pushing my Tim. Now you have me thinking about changing it.
     
  13. Ed Reed

    Ed Reed Senior Member

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    These are simple and cheap mods to try. Also easy to remove to return the pedal to "stock".
     

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