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out

DOD 250 Overdrive

The DOD 250 Overdrive is a semi-vintage circuit in that its been around

since the mid-70s. It uses a single opamp to amplify the signal and then

uses a pair of diode clippers in asymmetric arrangement to generate an

overdriven sound. Take a look at the MXR Distortion+ project--you’ll see

that is almost identical to this one.

Mods!Diode clipping mods: try different values for D1, D2, and D3. Try different diode

types and LEDs.

The standard LM741 single opamp is a low-performance part: it is noisy and not

audiophile-grade. Which makes it just about perfect for an overdrive. Try other

single opamp parts. You can also use half of a dual opamp to play around with

different values.

The original circuit uses a B500K reverse log pot. If you want to adhere 100% to

the original, buy that value. But it won’t make a huge difference in tone.

The 22pf capacitor tames a bit of high-end in the feedback loop of the opamp (the

loop between pins 6 and 2). It also helps keep the circuit from oscillating. Try

different values here to see if you can make it sound better.

beavis board project

A100K

Volume

A500K

Gain

C2

10nF3

2

7

6

4

+

-

U1

LM741

Input

9 volts +

C4

4.7uf

R52.2MΩ

R610KΩ

R1100Ω

R222KΩ

R322KΩ

C1

10uFR4

470KΩ

R910KΩ VR2

A100K(volume)

OutputD1

1N4148

D2

1N4148

D3

1N4148

C6

1nF

R81MΩ

C5

22pf

C3

4.7nfR7

4.7KΩ

VR1A500K(gain)

LM741

in

10uf

+

100Ω

22KΩ

22KΩ

470K

2.2MΩ

10nF

10KΩ

1MΩ

22pF

4.7nF

4.7KΩ

1N4148

1N4148

1N41

48

1nF

4.7uf

+

10KΩ

revision: 1.1 18 dec 2008 © 2008 beavis audio research