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out

MXR Distortion +

Originally released in the mid-1970's the MXR Distortion + has been a

popular pedal ever since. The gain is a bit less than what most of us would

consider as distortion, but the circuit is simple enough to provide ample

room for modifications. Take a look at the DOD 250 Overdrive project--you’ll

see that is almost identical to this one.

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

and LEDs.

The standard single opamp is a 4558 dual opamp (only one of the opamps is

used). Use either the JRC or the RC version. Or use any other dual opamp.

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

100% to the original, buy that value. But it won’t make a huge difference in tone.

The 10pf capacitor tames a bit of high-end in the feedback loop of the opamp (the

loop between pins 1 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

8

1

4

+

-

U1

4558

Input

9 volts +

C6

1uf

R410KΩ

R11MΩ

R21MΩ

C1

1uFR3

1MΩ

R710KΩ VR2

A100K(volume)

OutputD1

1N914

D2

1N914

C6

1nF

R61MΩ

C5

10pf

C4

4.7nf

VR1A500K(gain)

4558

in

1uF

+1MΩ

1MΩ

1MΩ

10nF

10KΩ

10pF

4.7nF

1N914

1nF

1uF

+

10KΩ

C3

1nF

R54.7KΩ

1nF

1N91

4

1MΩ

4.7KΩ

revision: 1.1 2/18/2009 © 2009 beavis audio research