Behringer UD100 Ultra Distortion
| Power Input | 9V |
| Bypass | Buffer |
| Audio In | 1 |
| Audio Out | 1 |
| Board | PCB414100REVB |
| Revision | B |
| Date Code | 1305 |
| Brand | Behringer |
| Manufacturer | Eton |
The circuit board on this pedal is a hybrid through-hole surface mount design, with the through-hole parts on top and surface mount components on the bottom. The through-hole components still have to share space on the bottom side, so most of their pads are fiddly and small, making solder removal more difficult than usual for through-hole, but still easier than most surface-mount work.
Original Capacitors
Most or all original electrolytic capacitors were Xunda brand. Some values may have changed during board revisions, or even between revisions. Even the ID numbers on the board may have changed. All of the capacitors are tall and skinny to fit on the board; there are a lot of capacitors next to each other.
| ID | Farad | Voltage | Cap Type | ⌀/Width | Height | C1 | 10μF | 16V | Electrolytic | C2 | 0.22μF | 50V | Electrolytic | C3 | 10μF | 16V | Electrolytic | C4 | 10μF | 16V | Electrolytic | C5 | 1μF | 50V | Electrolytic | C6 | 1μF | 50V | Electrolytic | C7 | 0.047μF | 100V | Film (Green) | C8 | 1μF | 50V | Electrolytic | C9 | 1μF | 50V | Electrolytic | C10 | 1μF | 50V | Electrolytic | C11 | 1μF | 50V | Electrolytic | C12 | 10μF | 16V | Electrolytic | C13 | 100μF | 16V | Electrolytic | C14 | 47μF | 16V | Electrolytic | C15 | 100μF | 16V | Electrolytic | C16 | 10μF | 16V | Electrolytic | C17 | 10μF | 16V | Electrolytic | C18 | 10μF | 16V | Electrolytic | C19 | 10μF | 16V | Electrolytic |
|---|
That lone green film capacitor at C7 may be the most straightforward modification you can make to alter the sound.
In C2 is a 0.22μF electrolytic capacitor that dictates how much bass enters the gain and clipping circuitry. Upping the capacitence a bit here can allow more bass to enter. A higher quality capacitor here, especially if you can find a film cap that will fit in the top-right corner of the board, will potentially improve your ability to hear differences between notes. The electrolytic capacitor can introduce distortion of its own, reducing the clarity of the crafted distortion you are aiming for with the pedal. If you can't find a film cap that will fit, a low-ESR electrolytic (that fits in this corner) will still be a step in the right direction.
Original Transistors
Some values may have changed during board revisions, or even between revisions. Even the ID numbers on the board may have changed.
| ID | Part# | Batch | Type | Pinout |
|---|---|---|---|---|
| T1 | J112 | 415 | N-Channel JFET | D-S-G |
| T2 | J112 | 415 | N-Channel JFET | D-S-G |
| T3 | J112 | 413 | N-Channel JFET | D-S-G |
| T4 | J112 | 415 | N-Channel JFET | D-S-G |
| T5 | J112 | 413 | N-Channel JFET | D-S-G |
| T6 | J112 | 413 | N-Channel JFET | D-S-G |
| T7 | J112 | 412 | N-Channel JFET | D-S-G |
| T8 | J112 | 412 | N-Channel JFET | D-S-G |
| T9 | J112 | 412 | N-Channel JFET | D-S-G |
Original Controls
Switches and dials for reference on the board.
| ID | Brand | Type | Pins | Positions |
|---|---|---|---|---|
| SW1 | Comax | Switch | 12 | 2 |
| SW2 | Unknown | Momentary | 4 | 2 |
| VR1 | Alps | Dial | 5 | 300° |
| VR2 | Alps | Dial | 5 | 300° |
| VR3 | Alps | Dial | 5 | 300° |
Original Diodes
Switches and dials for reference on the board.
| ID | Pins | Notes |
|---|---|---|
| D1 | 2 | Silver band towards D1. |
| LD1 | 2 | Red. Plastic stand-off. |
Repair
When opening this pedal on July 26th, 2026 for the first time in over a decade, Steve discovered capacitor C13 was blown out.
Capacitor Changes
These changes may yield unexpected consequences for your board. They may even for my board, and haven't happened yet! Alter your pedal at your own risk.
| Board ID | Farad | Voltage | Cap Type | ⌀/Width | Height |
|---|
Transistor Changes
No transistors were replaced or modified.
- 1 Capacitor was mounted unconventionally to fit properly or to avoid other components.