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Distopia
About
Distopia is a DIY distortion pedal, mainly for guitar and bass. This page contains the building instructions.
This pedal was designed in collaboration with the SheWolf music band, for their use.
The circuit is loosely based on the Boss DS-1 circuit but has moved quite far away from it during design. However, the idea remains broadly the same.
Above, the first model, a fully working prototype.
And above, an early test version of the circuit, on breadboard.
Resources
Bill of materials
| Name | Qty | Value | Specific contraints or model |
|---|---|---|---|
| C1, C3, C5, C13 | 4 | 100nF | Film, pitch 5mm, 7.2×4.5mm² |
| C2, C8, C14, C24 | 4 | 1µF | Film, pitch 5mm, 7.2×4.5mm² |
| C4 | 1 | 100pF | Ceramic, pitch 2.5mm |
| C6, C23 | 2 | 100µF | Electrolytic, 25 V, pitch 2.5mm, ⌀6.3mm, low ESR |
| C7 | 1 | 250pF | Ceramic, pitch 2.5mm |
| C9 | 1 | 470nF | Film, pitch 5mm, 7.2 × 4.5mm² |
| C10 | 1 | 10nF | Film, pitch 5mm, 7.2 × 7.2mm² |
| C11, C29 | 2 | 15nF | Film, pitch 5mm, 7.2 × 7.2mm², accurate value if possible (≤5%) |
| C12, C28 | 2 | 68nF | Film, pitch 5mm, 7.2 × 7.2mm², accurate value if possible (≤5%) |
| C15 | 1 | 47µF | Electrolytic, 25V, pitch 2.5mm, ⌀ 6.3mm, low ESR |
| C16, C19, C25, C26, C27 | 5 | 100nF | Ceramic, pitch 2.5mm, doit loger dans 2.5×5mm², hauteur 4mm max. |
| C17 | 1 | 22nF | Ceramic, pitch 2.5mm |
| C18, C20, C21 | 3 | 47nF | Ceramic, pitch 2.5mm |
| C32 | 1 | 2.2nF | Film, pitch 5mm, 7.2×4.5mm² |
| D1 | 1 | LED | 5 mm, red, low current (1–2mA) |
| D2, D4, D6, D7, D8 | 5 | Small signal silicon diode | 1N4148 |
| D3 | 1 | LED | 3mm, red, standard (20–40mA) |
| D5, D9, D10, D11 | 4 | Germanium diode | 20V, 1N34A |
| D12 | 1 | Zener diode | 18V, 1N4746A |
| J1 | 1 | 2.1mm male power jack socket | Panel mount, insulated from the enclosure |
| J2 | 1 | Socket for 9V battery | |
| J3 | 1 | Momentary SPST footswitch | Soft touch |
| J4 | 1 | 6,35mm stereo female jack socket | Panel mount, Neutrik NYS230 |
| J5 | 1 | 6,35mm mono female jack socket | Panel mount, Neutrik NYS229 |
| J6 | 1 | Toggle switch SPST | Panel mount |
| Q1 | 1 | JFET-N | TO-92, pinout: DSG, J201 |
| Q2, Q10 | 2 | NPN | TO-92, pinout: EBC, 2N5088 |
| Q6, Q7, Q8 | 3 | JFET-N | TO-92, pinout: DSG, 2N5457 |
| Q9 | 1 | MOSFET-P | TO-251-3 or TO-220-3, pinout: GDS, low Rds, Vds −30V, NTD2955-1G, IRFU5505PBF or IPP80P04P4L-08 |
| R1, R11, R22, R44 | 4 | 1kΩ | |
| R2 | 1 | 2.2MΩ | |
| R3, R34 | 2 | 3.3kΩ | |
| R4, R10, R20, R23, R26, R39 | 6 | 100kΩ | |
| R5, R19, R27, R32, R33, R36, R40 | 7 | 1MΩ | |
| R6 | 1 | 150kΩ | |
| R7, R21, R28 | 3 | 330kΩ | |
| R8, R18, R25, R35, R41, R42 | 6 | 10kΩ | |
| R12, R38 | 2 | 10Ω | |
| R13 | 1 | 820Ω | |
| R9, R14, R15 | 3 | 2.2kΩ | |
| R16, R17 | 2 | 6.8kΩ | |
| R24 | 1 | 8.2kΩ | |
| R43 | 1 | 120kΩ | |
| R45 | 1 | 330Ω | |
| R46 | 1 | 100Ω | |
| R50 | 1 | 82kΩ | |
| RV1 | 1 | 10kΩ potentiometer | Linear, ⌀ 16mm, vertical on PCB, 16mm min pin length. Alpha 16mm type 4 |
| RV2 | 1 | 250kΩ potentiometer | Inverted logarithmic (C type), ⌀ 16mm, vertical on PCB, 16mm min pin length. Alpha 16mm type 4 |
| RV3 | 1 | 10kΩ potentiometer | Inverted logarithmic (C type), ⌀ 16mm, vertical on PCB, 16mm min pin length. Alpha 16mm type 4 |
| RV4 | 1 | 50kΩ potentiometer | Linear, ⌀ 16mm, vertical on PCB, 16mm min pin length. Alpha 16mm type 4 |
| RV5 | 1 | 100kΩ potentiometer | Logarithmic, ⌀ 16mm, vertical on PCB, 16mm min pin length. Alpha 16mm type 4 |
| RV6 | 1 | 500kΩ potentiometer | Linear, ⌀ 16mm, vertical on PCB, 16mm min pin length. Alpha 16mm type 4 |
| U1, U2, U4 | 3 | Operational amplifier | Dual, low noise, DIP-8, NE5532AP. U4 has less requirement on noise and can be just a NE5532P. |
| U3 | 1 | Hex schmitt trigger | DIP-14, CD40106BE |
| U1, U2, U4 | 3 | IC socket, DIP-8 | Hollow body in order to put a 100nF capacitor inside |
| U3 | 1 | IC socket, DIP-14 | Hollow body in order to put a 100nF capacitor inside as well as two resistors |
| Wire | About 1m | Insulated. At least 0,25mm² (AWG 23), preferably stranded. | |
| Enclosure | 1 | 1590BB ou équiv. | Eddystone 29830PSLA |
| Knobs for the potentiometers | 6 | ⌀ 6mm shaft, with screw | |
| PCB | 1 | See below |
Important notes:
- Components must be at most 15mm tall so they fit in a standard 1590BB enclosure.
- If the MOSFET is in TO-220 package, it must be bend so the top does not touch the enclosure base. TO-251-3 package fits vertically but the legs must be slightly twisted to enter the holes because their spacing is different of the TO-220.
- Resistors and diodes (excluding LED) must be at most 7mm long (5mm for D6 and D7). If not, they must be soldered vertically.
- Resistors must accept at least 1/4W.
- Resistors should be 1% accurate, particularly R43 et R45. But most of the time 5% is still acceptable.
- Potentiometer knobs must fit their shafts. Make sure they will not touch each other.
Count about 50€ of good quality components.
Tools: soldering material, cross-head screwdriver, cutting pliers, drill, drill bits from 3 to 12mm for the metal, round file for the metal, a set of wrenches or adjustable wrench, tools to strip wires, insulated tape, metal saw.
Schematics and PCB
Electronic schematics, Gerber files for the print, layouts and KiCAD 8 source files are located in the following archive: distopia-2024-06-23.zip (3517 kB). Pictures below are for illustration purpose only. Use the files from the archive as reference.
I can provide PCBs at cost price + shipping fees. Please contact me if you are interested.
Building instructions
Enclosure
The pedal is put together pretty tight in a 1590BB enclosure. There is no room for a battery, power supply must be external. However the circuit has been designed for battery so it could fit in a slightly bigger enclosure. The board is attached with the potentiometers but there are mounting holes if you need it to be mounted differently on the enclosure. The jack sockets must be located at the bottom of the enclosure. The power jack and the Dry/mix switch are located at the top, between two potentiometers, and as close as possible to the base so their pins will not make contact with the board. Holes must be placed as accurately as possible.
Panel artwork is available here (29MB). To be printed on self-adhesive transparent paper. Clean and wipe the enclosure, stick the artwork then add several layers of varnish to protect it.
Circuit
Solder the components sorted by height.
The order is given by layout.ods (order for film capacitors may
vary depending on the parts).
This file indicates the position of each component on the board, too.
This point require some care: R26 and R27 are intended to fit in the socket of the CD40106. Because the socket thickness may vary, make sure that everything fits well before soldering. If not, it is possible to file down the inner edges of the socket. Or to solder the resistors once the socket is set up.
One more thing: be careful when bending the legs of the 1N34A diodes. Indeed, the legs are to be bent right at the end of the glass enclosure. However the package is very fragile and could break if the legs apply too much pressure on it. In doubt, solder these diodes vertically.
The D3 LED (on the component side) has no visual use, so it can be soldered at any height.
Carefully cut the legs of components that will overlap with the potentiometers. Cut the wires to the right length and solder them to the PCB, connectors and switches. Don’t connect the audio output ground wire, it could make a ground loop with the conductive enclosure.
| Connection | Number of wires | Length |
|---|---|---|
| Audio input | 3 | 6cm |
| Audio output | 1 or 2 | 7cm |
| Footswitch | 2 | 6cm |
| Power jack | 3 | 5cm |
| Dry/mix switch | 2 | 12cm |
Assembly
With cutting pliers, cut the anti-rotation bits from the potentiometers and the rotative switch. Fasten them to the enclosure, without tighten so they can move easily. Be careful not to mix up the different kinds of potentiometers. Ajust the potentiometers by fitting the PCB on them, but without soldering at the moment. When the PCB is fitted, fasten the potentiometer nuts.
Now remove the PCB and cut two strips of insulating material to be inserted between the potentiometers and the PCB, in order to avoid any short. I used offcuts of transparent sheets, but any other material would be fine.
Put the LED and fit the PCB again on the potentiometers. Solder them, as well as the LED. Avoid the LED to stick out too much, to protect it from impacts. Fasten the other connectors and switches. The Dry/mix switch should have its wires on the Dry side.
When everything is ready, screw the knobs on the pot shafts. To avoid fastening them too low (which can cause friction and blocking), you can insert small elements between the top of the shaft and the bottom of the knob. For example, I used a sheath from a thick electric cable, cut into 5mm pieces.
Use
The user manual is available here (PDF, 496 kB).
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