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MXR Distortion Effects Project

All FX Pedals
   

 

The three pedals pictured above are an original 1970s MXR Distortion (Left), JN Modified Distortion (Middle) and JN Vintage Distortion (Right).

These were the first attempts to make effect pedals from scratch. The PCB was drawn by hand with a Dalo etch resist pen then etched using Ferric Chloride.
All parts were bought from a local electronics retailer.

The 70s MXR Distortion was bought 24 years ago (second hand) for £22, it has survived countless gigs and practices. It produces a smooth warm distortion. The track layout and components were the basis for the other two pedals.

I had a schematic from the internet but the layout was different from the MXR, so I copied the MXR tracks and matched the components to a list from the web.

Modified Distortion
It has twice the amount of old style diodes in series, which produce more cleaner increased output, but still give a mild, smooth overdrive, an increased value output pot, a newer IC which gives a clearer signal with less hiss and an increased input and an increased value Capacitor which filters less bass frequency giving a fatter sound.
Overall the sound is very good it has more output, more sustain and better clarity / response than the original MXR. This was constructed in a Die Cast case.

Vintage MXR
Is based on the same components as the original and it sounds very much the same.
This now belongs to my son who wanted a red transparent case and knobs off a Telecaster. Not very Vintage looking but has the Vintage sound.

Test Pedal (Not shown)
Is a copy of the modified one but with Silicon diodes which give more distortion but sounds harsh and scratchy, it has a lot more fizz.
This may be converted to the modified spec above as a backup/spare.

Technical Spec

 

MXR / Vintage

 

Modified 1

Modified 2

Diodes

2 x 1N4148

2 x 1N4148

4 x 1N914

IC

LM741

TL071

TL071

Pot (Volume)

10 Ohms

47k Ohms

100k Ohms

Pot (Distortion)

1 Meg

470k Ohms

1 Meg

Input Capacitor

10k

47k

47k



MXR Distortion Components Photo
MXR Distortion Tracks Photo

MXR - Components

MXR - PCB Tracks
JN Distortion Components Photo
JN Distortion Tracks Photo

JN - Components

JN - PCB Tracks