FXdoctor Custom Effects is a Boston, Massachusetts-based builder and modifier of guitar effects pedals, operated by Joshua, who has been building, customizing, and repairing pedals and amplifiers since 2001. The shop focuses on small-batch custom effects, modifications to existing production pedals, and rehousing services for players attached to vintage tones.

The product line includes original designs such as the Super 8-Bit Fuzz — a high-gain, heavily gated fuzz known for its staccato, keyboard-like note attack — along with the Scalpel Volume, Booster Shot, Apache Tremolo, Super Mario Fuzz, and the 50 Output Volume Pedal. FXdoctor also produces one-off takes on classic circuits (Doctor Quack, Destructo Dirtbox, Range-Man Boost, BIG Boost, Modded Rat 2), channel switchers, and Yellow Jacket Tube Converter Sockets.

The operation is also recognized for its modification work, particularly Phase 90 mods and Whammy true-bypass conversions, as well as creatively designed enclosures including a Tetris-inspired series.

FXdoctor has 1 product cataloged on Equipboard, including Bass Effects Pedals.