Home Forums GuitarPCB Build Support mkc3 drive tone

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    Just got mine running on the bench. Using the trimmer mod and off board ultra gain on a separate footswitch (two wires from r15 to the center of a dpdt footswitch and a 10k/47k on the opposing legs of the switch).


    It sounds semi similar to my other brand Klon style builds but I could use help with a tweak or two.

    The main issue I am having (this will be hard to describe without a soundclip) is the gain has a bit

    too much sizzle or fizziness to it especially on the trailing end or decay side of a chord.

    Its very close to the sound like when the clipping diodes are not installed but obviously not that harsh.

    I am using 2x1n34a from the guitarpcb store and a pair of older tl072cn.

    Any tweaks to caps or resistors I can try to take out some sizzle?

    How about anything on the ic side?

    Thanks in advance.


    Change (increase) the Ultra Gain resistance per the Build Doc. Different rigs & pickups will yield completely different results (not to mention personal taste) so it is suggested that you adjust the Ultra Gain resistor till it is right for you, your ears and your rig.

    That said the resistor could even be a 25k potentiometer or use a potentiometer (or standing trimmer) to find the desired resistance and measure it. Then use that value as your resistor. If it is socketed then just try different values. I would also not make practice of using the Ultra Gain Mod at the same time you might have the personal MKC Gain controls cranked. Finally pedal position is extremely important so always try the pedal outside of any chain first.

    Keep in mind if you are running the MKC Gain Control up high and then use the Ultra Gain mod switch I would expect it to get fizzy using high output pickups. I always use Vintage Wound Pickups so while 8k is good for me Higher Output pickups may require more than 10k of resistance. Try 12k, 15k or even 22k…

    I hope that helps.

    Below is from the Build Document:

    You can use it with just a DPDT On/On Toggle switch and choose between stock (R15– 47k) and Ultra Drive Mode ranging anywhere between 4.7k to10k. I like 8.2k in mine. Socket and see!
    If you use my DPDT wiring board you can easily socket the Mod side and choose the correct value you like best for your personal rig and taste.
    Here is a Customer demo to show you the Main control settings at about 4:00 minutes in. If your circuit reacts differently after trying my suggestion then there also could be a build issue.


    Geez…sat down with my coffee this morning and c6/c3 are tagged 682j.

    I have 10 of these in a bag from Ebay labeled 68n.

    I need to check my math…but I am pretty sure 682 is 6.8n.

    Hours lost lastnight…lol


    This page is good for checking:


    There is a chart available and 682 is 6.8nF

    I would recheck everything.



    Yep…looks like that’s the only issue so far.

    Worked the diodes pretty hard last night pulling them in and out of sockets/swapping like 25 times.

    Might order another set of them while I am at it.

    Thanks for the quick help Barry.

    Pedal did not sound “right” (just about everything I have built of yours is dialed right out of the gate)..I knew it had to be human error after sleeping on it.

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