Klon circuit experts [tech question]

Discussion in 'Effects, Pedals, Strings & Things' started by snow and steel, May 5, 2015.

  1. snow and steel

    snow and steel Supporting Member

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    If one wanted to increase the amount of Distortion/drive/gain [however you want to name it - not the volume], what parts could you change in the existing circuit to accomplish that? By that I mean remove one part and replace it with another [or in other words - not designing a new board just modifying an existing klone] Specific resistors, caps or potentiometer values by chance? I've built my share of pedals but the design aspect of this circuit is a touch past me. thanks!~
     
  2. manticorefx

    manticorefx Member

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    Try lowering the 2k resistor.
     
  3. snow and steel

    snow and steel Supporting Member

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    Lets say we wanted roughly another 15% increase I gain. Lowering it to.... what exactly? thanks!
     
  4. manticorefx

    manticorefx Member

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    Try 47R to start with. That's what the Silver Pony has in that spot. If you want even more, go lower. Maybe 15R or 10R. You could put in a trimpot for extra versatility.
     
  5. coltonius

    coltonius Señor Member Silver Supporting Member

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    Interested.. Subscribed!
     
  6. rumbletone

    rumbletone Silver Supporting Member

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  7. Whiskeyrebel

    Whiskeyrebel Member

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    Why wouldn't you just hit its input with a larger signal? Why change parts?
     
  8. coltonius

    coltonius Señor Member Silver Supporting Member

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    That would require another pedal!

    I know Rawkworks used to make a higher gain adaptation of the circuit (Night OD). According to the info I found, the Night had a tweaked midrange and an internal toggle for silicon / BAT41 diodes. Source can be found here, so you know I'm not pulling this info out of thin air.

    So if I were to do it, I'd probably add a High / Low gain toggle somehow to swap the necessary components, or start with a "4th knob mod" to adjust that aforementioned resistor. That being said, I'm not currently proficient in Klon circuit topology like others, so the who/how/what is currently beyond me.
     
  9. mrclean77

    mrclean77 Supporting Member

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    Goose it with an SHO.
     
  10. midwayfair

    midwayfair Member

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    ZUse the sunking II schematic (I don't have Ken's handy to use his part numbers):
    http://www.madbeanpedals.com/projects/Sunking2/Sunking2.pdf

    The gain is a function of multiple components. IC1B is the "dirt" gain stage.

    The gain of the op amp stage for all frequencies is R9 (2K) PLUS the current resistance between pins 2 and 3 of the gain pot divided into R7 (422K) plus 1 because it's a non-inverting stage (which has a minimum gain of 1). Gain is 212x at max.

    However, some frequencies are not at full gain. C7 bypasses R8 (15K), so higher frequencies have more gain than lower frequencies; for very low frequencies, the gain is never higher than 25x (that's 24x + 1).

    The incoming signal size is R6 divided against the current resistance of the gain pot, or a minimum of 10% attenuation at full gain. The gain pot is also a variable state high-pass filter with C4, meaning that the amount of bass goes up as you turn up the gain, until there is no bass cut from the incoming signal.

    R7 and C9 also form a low-pass filter that removes treble above 1KHz.

    Finally, the clipping diodes require some resistance to conduct, which is provided by R10. That one's probably not worth playing with.

    There's a difference between gain and distortion. The op amp will put out the full 9V long before it reaches the highest gain setting, so your signal will never be clipped more by the diodes than it already is. The only additional distortion you can get will come from clipping the op amp. Is that what you want? If so then you can increase the gain.

    A 15% increase in gain is very likely to be ... disappointing, to say the least. I think Manticore's suggestion of the 47R from the Silver Pony might be overkill, though ... that puts the gain closer to 9000x. (Seriously.) Let's just look at doubling the gain.

    Changing R9 to 1K is the easiest change. This will double the actual gain without making any changes to the filters. However, the 1KHz low-pass filter will still be in effect, so if the gain is going up for everything that's only 1KHz or lower ... well, you should be able to see that means that increasing the raw gain means that you're losing treble. We might be okay with that, but it's not going to just be 'more gain, no other changes.'

    What happens if we instead double the 422K? Let's use 820K because that's an easy to find resistor. Well, that's going to make the problem worse. Now our cutoff frequency is half as high (500Hz), and we've still doubled the gain -- we're actually losing EVEN MORE treble.

    We could play around with the 15K (R8) as well, but that's only going to change the gain for the lower frequencies. We probably want to leave them alone ...

    Wait. I forgot a calculation. Decreasing the 2K to 1K ALSO changes how much BASS is in the signal. R9 forms a high-pass filter with C7 ... it was 1KHz boost (da fuq? we were just talking about that being the cutoff of the op amp ... OHHH, okay, that means that there's a bass cut at 1KHz and a treble cut at 1KHz -- a midrange peak at 1KHz! Not exactly "low mids" though, is it?). Anyway, let's run that through the filter, and we get about 1.9KHz by changing R9 to 1K. That's looking even less appealing.

    What I'm getting at is this:

    Just changing a resistor or two is not going to just give you more of what's already there. You will also need to replace a capacitor.

    If you want to change the 2K to a 1K, you will have to change the 82nF cap (double the capacitance to keep the same filter). If you're going to change the 422K to an 820K, you have to change the 390pF cap (cut the capacitance in half to keep the same filter).

    Of course, keeping the same filters but adding more gain doesn't necessarily mean you get "more of the same with more distortion." Distortion reacts to the presence of different frequencies differently, so having the same amount of treble or bass in a more heavily distorted signal could lead to unpleasant artifacts. Of course, you won't know that until you start messing around with it.

    You can get sockets for components pretty cheaply. You could socket everything in the feedback loop of IC1B and tinker to your heart's content.

    Sorry for the double post earlier. Mobile bug I guess.
     
    Last edited: May 7, 2015
  11. coltonius

    coltonius Señor Member Silver Supporting Member

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  12. snow and steel

    snow and steel Supporting Member

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    Awesome!

    I think that got me past where I was stuck - thank you very much!

    I wasn't going to do this to a MO [Ken has them pretty well tuned perfectly], but rather a couple of oddball klones I have laying around that I positively detest. I figured that if I destroyed them I'm out nothing as I already hate them and don't use them. This is more a study in pure academia than anything else.
     
  13. billyg121

    billyg121 Supporting Member

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    Ken could probably custom make it.
     
  14. Comfort Player

    Comfort Player Silver Supporting Member

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    Fantastic post Jon. I will have to give these values a try to see what comes of it. Maybe I will send it to SandS to add to his collection. Maybe a white one this time :drool



    Changes (rounded to more common values )
    2k --> 1k
    82nf --> 150nf
    422k --> 820k
    390pf --> 200pf


    Sure I can do that. :beer
     
  15. snow and steel

    snow and steel Supporting Member

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    Ken, If you're game then I am!

    I'm thinking the capacitance is really the stickler here - I had NOT considered ANY of the actual caps being changed. For some reason I had it stuck in my head that pots and resistors were the whole thing.

    I'm going to a try a few of these changes of a real KRAP KLONE I have [and hate] and will see if anything interesting happens [although I know just enough to be dangerous]. Ken probably has a lot more in the "real knowledge" department than I do. I've always been more of a "meter the crap out of everything and change parts till I find the reading I like" kind of guy, ha ha!

    I DO have a pretty early white one - # 204 [chicken head knobs came on this early one]. Or is this color Cream?

    [​IMG]


    The really sad part is that for all the MO's I have acquired - I have three times as many klones sitting in a box that I completely detest. And I have quite a few MO's!

    [​IMG]
     
    Last edited: May 7, 2015
  16. twp

    twp Likes guitars; loves music... Silver Supporting Member

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    I don't know how Rawkworks does it, but I know they do it reeeel good. Night OD is the best.
     
  17. coltonius

    coltonius Señor Member Silver Supporting Member

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    Looks like these changes could be put on a 4PDT with a little clever wiring. That would make for an interesting edition!
     
  18. coltonius

    coltonius Señor Member Silver Supporting Member

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    21 crappy klones in the closet?? :thud

    I need a list..
     
  19. snow and steel

    snow and steel Supporting Member

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    Yeah about that, maybe a little more. Plus my KTR and Gold klon that I wasn't counting as part of that.
     
  20. Comfort Player

    Comfort Player Silver Supporting Member

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    Forgot about that early chicken head one you have. I still love those as I can work the knobs with my feet more easily


    I need to come up with a new color.
     

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