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Boss SD-1 GE
Keeley Mod


The SD-1 has great tone to start with. As with all of Robert Keeley’s modifications every component that is added is of the highest quality. Metal film capacitors are used in the SD-1 modification to provide the smoothest mid-range and high frequency. The overall bass response of the pedal has been increased as well. Metal film resistors are used in all of our changes to give each pedal a consistent sound with extremely low-noise. In addition we have improved the BOSS switching making it even closer to true-bypass! The SD1 Ge modification includes a two-way gain switch that lets you select between two different diodes for the clipping/distortion section of the pedal. The “down” position selects a germanium diode (the “Ge” part of the name). The Ge diode clips the signal more than a standard silicone diode. This provides a more saturated, compressed, and smoother sound with more distortion available. The “up” position selects an LED for the clipping section, which clips less, allowing a clearer, more “open” sound, with less compression, more dynamic response, and more available output. Both are asymmetrical and both are an attempt to make the pedal more “tube-like,” since tubes and transformers rarely produce a symmetrical distortion.

What you get with the Keeley SD-1 GE Mod!

1. Better bass response along with true mid range and high frequency transparency
2. Asymmetrical clipping for a more tube like distortion
3. Two-way toggle switch to go from germanium diode mode for fuzzier saturation to LED mode for a louder, more open tone
4. All of these mods make the SD-1 extremely versatile for lead and rhythm players

• All Controls set at 1 O’clock, toggle “down.” This will give you good biting drive and gain.

• Set the Level to 3 O’clock, Drive at 9 O’clock, and toggle switch “up,” and the tone anywhere that sounds good to you. This is a good boost and great for distorting the input of a tube amp.

• Set the Level to 4 O’clock, Drive off, and toggle switch “up.” This is an ideal clean boost.

• Set Drive to 4 O’clock and the Level to 12 O’clock and toggle switch “down.” This is a super GE sustain setting. Great for lead work that is very saturated while retaining the essence of your guitar!

All modifications are warranted for you, the original owner, for one year. If you have any problems at all please email Mammoth Electronics at If you are happy with this product, please let everyone know and tag us on Instagram and Facebook with #mammothelectronics. If you are not happy with this product for any reason at all, please let us know within 48 hours and we will refund your order. The entire Keeley and Mammoth team thanks you for your business. You’re keeping the good tones alive! If you like this product, there’s more where it came from, check out the rest of our products on

Mod times are 3-5 business days from the day that your pedal(s) arrive. Please ship to the address below:

Mammoth Electronics
Attn: Mods Department
3203 Broce Dr
Norman, OK 73072

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