How To Modify Effect Pedals For Guitar And Bass

Sure you can shape your guitar tone with an array of mass produced processors and stompboxes, but let it be known that you can't truly create your own signature sound without knowing how to modify effects pedals for guitar and bass. Don't worry if you don't have much electronic know-how, or if you've never played with a circuit board. The concept behind modifying effect pedals for guitar and bass is much the same as making your car better and faster-crack open the hood, swap a few parts, seal everything back up again, then take 'er  for a ride. For our example we're going to be modifying a Boss Heavy Metal MT-2 to add more bass. Here’s what you’ll need:

  • Soldering iron
  • Solder resin
  • Desoldering braid
  • .022uF capacitor
  • 1uF capacitor
  • Modification instruction sheet


  1. Find a modification instruction sheet.  The first step in making modifications to guitar and bass effect pedals is to find a detailed set of instructions that clearly lists every part you'll be swapping on your pedal. Those in the know aptly call this a "mod sheet." Mod sheets usually contain a form of short hand that corresponds to labels written on the pedal's circuit board. Next to the label of the part you're going to change is usually a section explaining what the swap will do. For our example, our mod sheet tells us to change the capacitor at C30 on the circuit board to a .022uF capacitor, and the capacitor at C6 to a 1uF capacitor. Swapping these will add more bass response to our pedal.
  2. Open the pedal. To begin modifying effect pedals for guitar and bass, flip the pedal over and unscrew the bottom plate. The Boss Heavy Metal MT-2 has four screws in each corner that we’ll remove to gain access to the circuit board.
  3. Locate the parts you want to swap. Once the bottom plate is removed, delicately pull out the circuit board and locate the C30 and C6 capacitors. Most pedal manufacturers make this fairly easy by putting a small label next to each component on the circuit board. For our example the C30 capacitor is near the bottom left, while the C6 capacitor is in the middle toward the top.
  4. Desolder the stock capacitors. To modify any effect pedal for guitar or bass, it’s first necessary to desolder the old components so they can be removed. This is best done by placing the desoldering braid over the soldered ends of the old components and heating it with your soldering iron until the braid completely soaks it up. Once you remove the stock capacitors from the MT-2, you should see two small holes in the circuit board where the capacitors were.
  5. Install and solder the new capacitors. Here’s where the MT-2 becomes a truly modified effect pedal. Taking your new capacitors, plug the .022uF capacitor in the open C30 slot and the 1uF capacitor in the C6 slot. Apply a new layer of solder around the prongs of these capacitors on the circuit board to complete the circuit. Plug the pedal into your guitar and test it. If everything went right, you will have successfully modified a Boss Heavy Metal MT-2 to increase its bass response.

There are literally thousands of little changes you can make on any one pedal like this that will have a thousand different effects. The real art in modifying effects pedals for guitar and bass is knowing what to change for the desired effect. Even though we only looked at one modification for one pedal, the essential process of modifying is the same for almost every type of stompbox. Keep in mind that it's a good idea to test the pedal after making every change, that way you'll know exactly where you messed up if something goes wrong. Most errors do in fact occur due to incorrect soldering, so practice your skills before you take on a big task! Now that you know how to modify effect pedals for guitar and bass, there's really no excuse not to find your own signature sound.

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