This ain't no Mickey Mouse distortion pedal!
This pedal is a clone of one on my favorite effects pedals from the 80's... ProCo's RAT Distortion. It's a basic OpAmp distortion pedal using the classic LM308N IC chip that is a fairly simple build for those handy with a soldering gun, have a free weekend, and love rock-n-roll.

The layout we are using was designed by Francisco Pena who has done an excellent job with this and other pedal designs on Tonepad.com. (please refrain from editing the circuit board artwork unless you have permission from the author. (sorry Francisco!!))

The schematic and PCB are available in PDF form at TonePad.com following this link , which also has a great library of other effects pedal and guitar related projects to build from beginner to advanced. You will also need the PDF for Off-Board Wiring for wiring the input/output jacks and power for the pedal.

TonePad.com also carries ready-made Printed Circuit Boards to purchase if you don't have the time or effort to make your own. The PCBs on tonepad.com come with a screen printed component side, tinned solder pads and also a solder mask - all for a pretty decent price considering the cost of supplies you have to buy to make your own! I recommend going this direction if you want as close to error free build as possible.

You can buy the majority( if not all) of the parts from Small Bear Electronics which offers pretty reasonable prices and are supporters of TonePad and several other DIY music project sites. (Also recommended!)

I created the graphics in Adobe Illustrator and have made it available below to all that wish to use it. It is a PDF file saved out of Illustrator so it is easily edited with any vector graphic software that can open pdf's..... have fun with it and go wild.

(I'll post some sound clips and maybe some video soon to give you an idea what it can do.)

Now lets get ready to Rat-n-Roll.....

Step 1: Getting the Goods....

The PDF file has the parts list along with the circuit board layout. This is not a RatShack project so you will have to order online from Small Bear Electronics or another reputable electronic parts dealer such as Digikey , Mouser , or MCMinone if you are not lucky enough to live in a city with a decent electronic parts store. I use metal film resistors instead of carbon film due to there tighter tolerance range (10% or 5% for carbon vs. 1% metal film margin of error) and if you buy an assortment online you can get them in bulk pretty cheap.

You can cross reference the IC's and transistors online at NTE to find the "generic" NTE version, which are usually easier to find locally. Audiophile types frown upon using NTE parts for high-end projects such as amplifier rebuilds do to inconsistencies in part specs but for projects like this I haven't had any problems so far.

Not stated in the schematic but is assumed knowledge is: All resistors are 1/4 watt , all capacitors need to be rated for 12 volts or higher. (a 12V .01uF capacitor and a 50V .01uF are the same except the 50V can take more voltage and will be bigger in size in case you were curious.)

In addition to the parts listed in the PDF file, you will also need:
- Qty. 3 - 100K-A (Audio or Logarithmic (same thing) Potentiometers - 17mm diameter fit better
(careful not to get Linear taper Pots.... big difference!)
- 3PDT stomp switch (Small Bear Elec, or Ebay)
- 9V battery snap and battery Clip,
- LED and LED holder (if you want a status indicator)
-1/4" Stereo input jack
-1/4" Mono input jack
-22 Gauge stranded hookup wire (preferable 3 different colors)
- 9V "wall wort" power supply (center conductor is " - ")
(this can be a salvaged one rated around 500 milliamps or so)
- power supply connector (female, that matches the connector on the power supply)
-Suitable case (preferable metal for strength and shielding.) Check the web.. Hammond cases are the most popular. I found mine at my local electronics part dealer.
*edit* My last trip back to the store I found out the company and the part # of the case...
The company is: LMB Heeger (they have a website also) and the case is # MDC532

Other Supplies & Tools:
Soldering iron, Solder, Drill/Dremel, Drill Bits, Clothes Iron, Plastic Containers, Rubber Gloves, PCB etchant (Ferric Chloride), Multimeter (for testing/troubleshooting), and cold beer.

About This Instructable


423 favorites


Bio: Jack of all trades, master of none, Sigh...... how does one get good at something when there are so many things in this world to ... More »
More by silverHalo: Retro Atari 7800 Mod: Sega Master System controller to Atari 2600/7800 hack Digital Thermostatic Beer Refreshment Regulator DIY Rat Clone Distortion Guitar Effect Pedal - The Dead RAT
Add instructable to: