This is a library of perfboard and single-sided PCB effect layouts for guitar and bass. I'm not an electrical engineer by any stretch of the imagination, just a DIY'er who likes drawing layouts. It is meant for the hobbyist (so commercial use of any of these layout is not allowed without permission) and as a way to give back to the online DIY community.

Friday, January 16, 2015

Zvex SHO - Crackle Okay

The Zvex Super Hard On has become one of the sought after boost pedals today. Derived from the preamp section of a 60s recording console, the SHO uses negative feedback to control the gain (which is what gives it the crackle when adjusting the knob). It's capable of being a clean boost and adding some sparkle to your tone, or pushing your tube amp to break up and creating a great overdriven sound.



If you want to add a master volume control to it, remove the 47k resistor and use a 50k pot. Lug 3 to the Out pad, lug 2 becomes effect out, and lug 1 goes to ground.

13 comments:

  1. Thanks for the great layout. Works great, built a few, interested in trying the Master Volume mod. What curve would you recommend for the replacement 50k pot?

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    1. Probably audio/log taper, though linear will work as well.

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  2. Hi! i think there is one mistake in reversed layout - insted of connection with D1 3 leg of the pot is connected to empty space just under second leg of the pot.

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  3. This schematic is a bit different of others schematics on internet.

    The schematic that I've seen on internet has 2 diodes 1n4148 (d1, d2) and hasn't zener.
    Do you know what is the effect of these diodes?

    http://www.luciferstrip.com/fuzz/sho-schematic.jpg

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    1. The diodes in both versions are to protect the MOSFET transistor. They both do the same thing, though I believe the zener does a better job of it. Zvex initially used 2, 4148s then switch to the single zener.

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  4. Hi friends. I have a trouble, when I move the pot I listen a noise. This is usual?

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  5. Great classic!
    For more volume range, I recomend to use 100k resistor intead the 47k one.

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  6. Do you have a schematic for this?

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    1. http://www.matsumin.net/diy/bunkai/Z_vex_SHO/Z.Vex_SHO_sch.BMP

      Basic schem there, though it shows the wrong diode.

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  7. On most layouts of sho, there are 10M resistors instead of 1M. What is the difference?

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    Replies
    1. If you look at the schematic linked above, you'll see the use of 1M resistors. Both work as they're essentially creating a voltage divider at the gate of the MOSFET. If it bothers you, just use 10M.

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