Distortion Plus / DOD 250

Models

This board can be used to make either a Distortion Plus or DOD Overdrive Preamp 250 as they are virtually the same circuit but with some component differences.

Components

Distoriton Plus

Parts
C1 1uF Electrolytic R1 1M D1-D2 1N4148
C2 10nF R2 1M D3-D4 1N270 (see notes)
C3 1nF R3 1M
C4 47nF R4 10K IC1 LM741
C5 1uF (see notes) R5 1M
C6 10pF R6 4K7 DRIVE 500K Reverse Log
C7 1nF R7 10K VOL 50K Log
R8 1M
CLIP SPDT Toggle Switch

DOD 250

Parts
C1 1uF Electrolytic R1 22K D1-D2 1N4148
C2 10nF R2 22K D3-D4 none
C3 1nF R3 470K
C4 47nF R4 10K IC1 LM741
C5 1uF (see notes) R5 1M
C6 22pF R6 4K7 DRIVE 500K Reverse Log
C7 1nF R7 10K VOL 100K Log
R8 1M
CLIP none

Build Notes

Clipping Diodes

There is space on the PCB for two different sets of clipping dioes which can be switched between by using a SPDT (single pole, double throw) toggle switch. D3 and D4 are bigger so should be able to accommodate the larger size of germanium diodes if you want to try them. The original pedals used 1N270 germanium diodes but 1N34A are good to try out. If you only want to use 1 set of diodes, you can solder a wire link between the top 2 holes of the switch pads to use D3 & D4 or if only using D1 & D2 then solder a link between the bottom two pads as shown below:

Capacitors

Where not specified, you can use either film or monolithic ceramic type capacitors. For electrolytics, it is advised to use ones with a voltage rating of 25V or higher. C5 on this circuit was originally a tantalum capacitor but you can use a monolithic ceramic cap instead and it won't make virtually any difference. If you do use a tantalum, the positive side is marked with a + on the PCB silkscreen.

Board Connections

The PCB connections are labelled as the following: I - Input, O - Output, V - 9V DC in, G - Ground

Potentiometers are connected from pin 1 to the square pad on the PCB. This board was designed so you can use right-angle board mount potentiometers on it if desired, otherwise you will need to solder wired from the pads to the correct pin/lug. Jack sleeves and DC centre pin should be connected to ground. V, LED + with a 2K2 resistor in series should be connected to the positive pin of the DC connector.