Introduction: DIY Rat Clone Distortion Guitar Effect Pedal - the Dead RAT

Picture of DIY Rat Clone Distortion Guitar Effect Pedal - the Dead RAT

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 (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 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. 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 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....

Picture of 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.

Step 2: Etching the Circuit Board...

Picture of Etching the Circuit Board...

There are several instructables and tutorials on the web on how to etch boards using the toner transfer method so I won't go into much detail here. I have found my tried and true method so you will have to experiment to find what works for you. I use the "glossy text" paper from FedexOffice's (they keep it behind the counter so you will have to ask for it) and print from their express computers to the B&W; Xerox Phaser 5500 printer. All FedexOffice's have this printer in there express area (at least at the time of this writing) and it lays down a heavy black coat of toner perfect for this process. The copiers (especially the Canon's) are horrible for this so I stick to what works.

Once you have your negative (reversed) image then you are ready to iron it on to the copper. I alway clean the board with fine steel wool (00 or 000) and then wipe it down with alcohol right before I begin to get the best adhesion of the tone to the copper. (In these pictures I am etching several boards to use in later projects). Place your image face down and with the iron set to nearly the highest (cotton) setting (no steam) lay the iron in the middle for a few seconds to melt the toner. This will tack it to the copper and stop it from sliding around as you begin to iron and apply more pressure. I generally work with the point of the iron moving from the center outwards, turning the board as I go. The process usually takes only 5 minutes of firm ironing until it is ready. With this paper I can see the toner outline coming through when it is almost ready.

We you are satisfied that you have it all melted then allow it to cool for a minute or two and then throw it in a bowl of hot/warm water to let the paper soak a bit. When the paper starts to buckle I start massaging it to gently loosen it up until it starts to peel. The goal now is to remove all the paper from the exposed copper. It isn't important to remove all the paper stuck to the toner traces just as long as there is no paper blocking any holes or bridging anything. I use an old soft toothbrush and under a running faucet to lightly scrub the stubborn paper particles that still remain.

Next I dry the board and under a decent light source I examine the traces for pinholes or scraped off toner spots and use a Sharpie marker to fill in any gaps or mistakes.

Now it is ready to etch... I like to warm my Ferric Chloride by placing my etching chamber in a bath of hot-ass water, this will speed up the copper removal time immensely. (With Ferric Chloride it is WISE to use gloves since it stains almost everything it touches especially human skin.) Drop the board in a wait a few minutes, then agitate the solution by swirling it around and then let it sit a spell more. Open a cold beer and drink while you are waiting. Repeat until all the exposed copper is de-solved, or run out of beer, then remove the board and rise off with cold water.

To remove the toner you can use Acetone or Car Brake cleaner but I just use a green 3M scotch pad and elbow grease. Voila! You now have a circuit board you made all by yourself!!
All that is left is to drill out the tiny holes and you are ready to start soldering. I strongly recommend using a drill press (Dermel has a nice one) for this process, it will save you lots of curse words that are better spent on crummy football games

Step 3: I Love the Smell of Solder in the Morning.......

Picture of I Love the Smell of Solder in the Morning.......

This is always my favorite part. Following the layout on the PDF I always start with Resistors first. If you don't know how to read a resistor I recommend printing a chart off the web for reference so you can keep the values straight and not mix them up during the build. You can also set your Digital Multimeter to Ohms and measure them individually, if your resistors are 5% tolerance then the resistance for a 100 ohm resistor could be 95 to 105 Ohms and still be in spec.

Next I move to the Diodes and the Capacitors. Current only flows one way through a Diode so watch the direction so you don't install it backwards. Ceramic and Film Capacitors aren't polarized so they can be soldered in any direction but the Electrolytic Caps (round can looking ones) are polarized so make sure that are placed correctly or they could explode. (There is usually a stripe running down the side of the can with a "-" sign that corresponds to the Negative leg of the capacitor. The circuit board layout diagram always has a "+" sign on it where the Positive leg goes.)

Although not on the parts list, I bought an 8-Pin IC Socket for the LM308 so I could swap it out with other Op-Amp chips later if I wanted to do any mods without having to unsolder anything. You can get a set of 2 at the RatShack for .69 cents... part # 276-1995. After the components are soldered then precede to the wires. I bought a three pack of 22 gauge wire at RadioShack that comes in Black, Red, and Green so I could keep the similar paths color coded for a fool proof assembly.

Solder the Pots to the wires next, paying attention to the order (this is where different color wires helps out. I like to twist similar wire bundles together to keep things organized and keep them out of the way. Remember that in the wiring diagram the pots are shown face down so keep that in mind when soldering.

Alrighty, lets lay out the case and stuff in all together!

Step 4: Case Layout and Stuffing the Beast!

Picture of Case Layout and Stuffing the Beast!

Now we have to figure out how we want to wire out pedal for power and bypass. The Off-Board wiring PDF has 6 different wiring setups depending on what you are after. If you can only find a DPDT switch you will have to use one of the schematics with the Millennium By-Pass setups which requires extra parts and a separate board which will eat up more space.

The Quickest and Easiest route is to get a 3 pole double throw switch (3PDT) from Ebay (the cheapest) or other guitar part sites on the web. With a 3PDT switch you can wire a LED without the hassle of adding a separate circuit board with the ByPass circuit. We will be using the Offboard Wiring 5 scheme for this project. This setup will allow for an LED, battery power, and for external 9V DC power.

Determine the best spot on your case for the input and output jacks. I like them in the back to keep the guitar cables out of my way when playing and for this case design it provided me with the most internal space. Use a spring loaded punch to mark the center of the holes, this will give you a center and will keep the drill bit from sliding around as you drill. Drill out these holes and also the holes for the 3PDT stomp switch, the 3 Pots, LED, and External power connector. You can build a cardboard mock-up of your case and play around with the placement of the parts before your drill if you are unsure of the fit. I used some thin gauge sheet metal to fabricate a bracket for the PCB mount that connects to the case via the center pot in order to not have to add any more holes in the case.

Now we solder all the wires to the jacks, switches, and power connectors as laid out in the diagram. Double check all the runs to make sure they are correct since it is easy to mix up wires in all this chaos. I temporarily mounted everything in the case to get an idea of the length of wires I will need to solder all the jacks and switches together.

Once the distances where measured and the wires were cut I took everything apart and soldered it together. I left the wires running to the 3PDT switch a bit long as to give myself some room to run them off to the sides in order to have room for the battery clip in between the board and the switch.

I used a thin piece of plastic to separate the battery from the exposed circuit board traces to protect from any short circuits in case they happen to touch each other.The plastic is bent like the circuit board attachment bracket and connects to the case using the holes drilled for the battery clip which is mounted to the bottom of the case.

Step 5: Rock-n-Roll!

Picture of Rock-n-Roll!

The graphics were designed in Adobe Illustrator and printed on transparent vinyl sticker material at my local FedexKinkos sign shop on their Gerber Edge 2 printer. Fast signs and other chain sign shops can print the same with any Vector graphics. Although not a permanent solution, I don't plan to Gig with this pedal so I didn't need anything of road worthy toughness. There are plenty tutorial on various stomp pedal websites and forums for case painting and labeling design so read up and go crazy.

Now plug it up to your guitar and amp and let the world hear the wrath of the DEAD RAT!!!!!

Check back later this year when I build a combo delay and chorus pedal in one case!!!


If you were careful during the PCB soldering and double checked carefully that no excess solder has bridged any traces, and all the solder joints are shinny and clean then you can rule out any board issues.

Some people have had bad LM308 chips that they bought from questionable sources (hmmm..... ebay maybe??) so if you have issues and didn't buy from Small Bear then this might be a good place to start troubleshooting. (This is another good reason to use a IC socket so you can easily swap out chips to test.)

If you have any hum, make sure the grounds are connected correctly. Using a metal case allows you to ground to the chassis which will help out a lot. Also you might want to buy shielded input and output jacks or make a metal shield out of thin sheet metal that covers the jacks to protect against any other electro-magnetic interference.


mhammond16 (author)2016-03-06

got started thank u for the instructable just need to find some drill bits

marrymay (author)2015-01-26

It`s very hard for me to find knowledgeable people in this particular topic, thank you for the pdf sharing, I like this post. and i recommand to do the DIY with this post's duide and in the meantime with another blog about distortion pedals, check here: Germanium Distortion Tone, it will help to understand this post.

chicalidude (author)2014-12-06

Can I use this one instead?

KacperK (author)2014-10-16

How to connect stomp switch?

The Hacker Artist (author)2014-05-01

For thoses looking for a LM308. They`re super easy to find on ebay.

Check out these sellers:



circusbrains (author)2013-11-20

How does the print shop handle your pcb layouts? Do you bring in a digital copy on a thumb drive , for example , or paper prints for them to copy from?

silverHalo (author)circusbrains2013-11-20

I believe they can only work from a digital file, such as an .EPS or other vector format.

Mtk87 (author)2013-09-20

Hi to all, sorry for the noob question, i just finished to build a pedal really similar to this (due to the difficulty and cost of the LM308, i searched for a similar one and opted for a NE5534).

I tried to see if it works (i'm on battery) but all I hear is a continous buzz (like if i were touching the cable with my hand) that is reduced whenever i play a note (but the note itself is not heard): can it be all due to the fact i haven't put it in a metal case: i know that basically that stuff can work as an antenna, but if feel strange that i get so much noise)

deadlyraven (author)2013-07-21

can you put some video of the fx?? i need to listen this fx before i make it :D

koroshjj (author)2013-03-28

How about 500k pots vs. 100k pots?
Also the circuit only has one transistor in it, which is a 2N series. what would an AC128 sound like in there? or some other transistors, like a germ one?

junkyardking (author)2013-03-05

Maybe I'm not searching right, but I can't find a 30pF cap anywhere. I tried Jameco, Smallbear, eBay and some local resources. I tried searching with the units converted to micro and nano, but even with that nothing comes up? Any hints at where else I could look?

silverHalo (author)junkyardking2013-03-05

pF = Picofarads.... 30pF = .03nF = .00003uF
smallest measurement to largest = Pico < Nano < Micro
Hope that helps....

Goldswordfish (author)2012-12-01

..and the final budget to create this?

silverHalo (author)Goldswordfish2013-01-06

I rarely keep track of costs since a lot of my parts are scrounged from broken electronics and dumpster finds. Plus, if I kept a paper trail of the true cost of my hobbies, my wife would never let me have them!

MUNSTER38 (author)2013-01-05

Hey where did you find the .001uF & .0033uF Capacitors. I cant find those on any of the suppliers that you mentioned. Do you have part numbers?

silverHalo (author)MUNSTER382013-01-06

These are available at the "Small Bear Electronics" link posted in the build notes. You are looking for "Polystyrene Capacitors" you can find them via this link as well ...

babakkamiyab (author)2012-05-19

hii. i cant download pdf file from your site can you help me and send it to my mail?

bzalavári (author)2012-04-16

Hi I would like to ask for the schematic if possible. Thank you in advance

silverHalo (author)bzalavári2012-04-19

Look in the first step, third paragraph... click on the link to for the schematic.

macboy98 (author)2012-01-23

hey dude , where is the pdf file for the circuit board , pls reply ASAP

Lexoo93 (author)2011-06-29

how do I have to change scheme #5 if I just want a DC input and no battery?

EPIC Kelly (author)Lexoo932011-11-20

Yeah, if anyone out there knows the answer to this one, I'd really like to know too.

silverHalo (author)EPIC Kelly2011-11-22

Just took a sec to look at the wiring diagram for "Offboard Wiring 5", which is what I assume you guys are referring to. I kind of confused to what you guys are asking about... if you don't need the battery, just leave out the 9v battery snap. The wiring doesn't change at would be the same if you wired it up with the battery snap and never connected a battery to it. Let me know if this answered your question.

EPIC Kelly (author)silverHalo2011-11-23

Thanks, that did answer the question. I figured that was the case, and tested it out and lo and behold it worked! Couldn't believe my mess of wires and solder and sweat actually worked. So, thank you for a very satisfactory project!

toxin20 (author)2011-08-08

hi silverhalo,

i just finished my rat build, very cool instructions, thank you!

i have a question about the sound though: when you strum some powerchord palm muted, does it have "punch"? because my build sounds a bit weird i think... palm muted it doesnt' have that certain punch its a bit more noisy than i think it should be.

the other question is about the potis: when i set any one of the potis to zero (doesn't matter which) i hear nothing. is that normal or is it an error in my build?

streetcrab_helmut (author)2011-07-01

Could you plaase tell me how you got the top of the PCB printed (with the shapes of the components to be fitted)?

The component screen was just printed on some clear sticker material and placed on the board before adding all the parts.
Good luck.

deco97 (author)2011-05-28

I was just wondering how you tell which side of the jacks is which?

icanmunch (author)2011-04-05

how should I be connecting the wires to the stomp switch? my switch has 1,2,3 down the left side of it if this helps. its only got 6 lugs on it

slapointe (author)2011-03-01

I am not building your box but changing one I own. I have a EXH Big Muff Pi with no ac jack. I cut the battery connect off and soldered a power jack to the existing wires then connected a 9v 300mA power adapter. Seemed logical to me until I turn it on to play. Sounds great playing but if it is on and I am not playing I get a lot of humming feedback from the pedal. Any ideas about causes or solutions?

silverHalo (author)slapointe2011-03-01

Hmmm, there are a few things that can go wrong. First, the AC power supply (9v 300mA) isn't actually 9v''s probably more like 12v or something close. "Wall wort" power supply's (as they are commonly refered to), vary in their voltage despite what they say on their label, this is because they rely on the internal circuitry of the device to regulate the voltage flow. Mainly, there is a voltage converter in almost all devices that can accept 10-15V and then steps it down to a clean and steady 9V for the device to use. To see this, test the power supply with a multimeter and note the true output voltage. So running it as you have it now is probably over-volting the circuit, which may or may not cause damage or weird happenings...hard to tell.
Secondly, AC voltage is noisy by nature. In order to clean up the noise of AC voltage, engineers design the circuit with filter capacitors and other goodies to clean out the AC ripple. Without these components, you will pick up the oscillations of the AC current and hear the feed back and hum.
Without a schematic of the circuit board it is hard to tell what you would need to do to clean up the hum....

aritoner (author)2010-05-01

 so i blew the last one and decided to try again but i noticed that in your picture your true bypass switch looks to almost have a square shape but mine has a rectangular shape the question is how do i know which way is the right  way to start soldering

silverHalo (author)aritoner2011-02-24

On a 3pdt (triple pole, double throw) switch there are 9 contact leads (3 rows of 3).
When the switch is on, the first lead on the top row and the first lead on the second row are connected. So if you tested it with a multi-meter on continuity setting you would get a "beep", stating that current is able to flow from one lead to the other. So the 1st lead of the top row and the 1st lead of the middle row, as well as the 2nd lead of the top row and the 2nd lead of the middle row and same for the 3rd lead. BUT, when the switch is off, then the 1st lead of the middle row connects to the 1st lead of the third row, and the top row is disconnected. Confused yet?
So if your switch is rectangle than the rows should go the long way across.... but you can test with a multi-meter just in case.

nellie18 (author)2010-12-01

nice project!

anyway, if you mind, may i ask if how many watts you used on your resistors?
and how many volts for the capacitors.

silverHalo (author)nellie182011-02-24

I probably used a mix of both 1/8 and 1/4 watt resistors. There isn't a whole lot of current flowing through the board so wattage isn't that important. 1/8 and 1/4 watt fit better than say a 1/2 watt resistor would.
The electrolytic capacitors need to be rated at least double the power supply voltage for safety. So for a 12 volt power supply you would use 24v caps or higher. You might get by with 12v caps but its always better to error on the side of caution.
Better safe that sorry.

Teburon (author)2011-02-01

love the graphics! but how did you get them onto the enclosure? did you use special transparent sticker paper or something?

silverHalo (author)Teburon2011-02-24

The stickers are printed onto transparent vinyl through a process called foil printing.
Pretty much any decent sign shop has the correct equipment to do that. Try your local Fast Signs, Signs-in-a-day, or FedexOffice(one that has a sign shop in it).
You can also also use "waterslide decals".. they make both lazer & inkjet waterslide paper that you can print your own graphics on. It's the same kind of material that they use to put the word "Fender" on the headstock of a Stratocaster. Google it, its a pretty simple process and has great results.

eduardrenz (author)2011-01-21

How can I buy an LM308 IC and IN IN914 Diodes? I live at Phillipines.. can u help me for my Project?? Eduard

silverHalo (author)eduardrenz2011-02-24

Ebay maybe? I would just do a Google search and find a company that will ship internationally.

lfebrero (author)2011-02-24

Hi man! I was wondering in wich direction I should put the 3PDT switch to make the connections according to the diagram #5 in tonepad.I mean, with the tips horizontaly o verticaly?? thanks

eduardrenz (author)2011-01-21

How can I buy an LM308 IC and IN IN914 Diodes? I live at Phillipines.. can u help me for my Project?? Eduard

olivero1 (author)2011-01-04

I have just completed this build. Your instructable was perfect and easy to use! This is my first build and I am very happy with the results. I used to own a ProCro Rat in the 80's and I believe that the distortion on this unit is even better than I remember! I used a Hammond 1590BB for the case and purchased the PCB from Tonepad. Now I am ready to make my own PCB's and move onto the Electric Mistress!

Thank you so much for your build notes!

oweng4000 (author)2011-01-01

What you should have done, would be call it the "deadmau5". Nerveless this was a great instructable, even if you did kill mickey mouse.

edgas10 (author)2010-08-24

hi im from portugal and knew to this stuff. i´ve order a lm308 but they made a mistake and send me a ca3080e. can you tell me if its possible to use it instead of the lm308? i know that they have not the same pinout. thanks edgar.

MetalheadGautham (author)2010-06-22

What difference would it make if I use carbon resistors instead of metal film resistors and UA741CN instead of LM308 to cut costs ? And yeah if I use a throw away plastic box and then wrap the whole thing with food grade aluminium foil, would it still work ? I mean the shielding...

There isn't really a lot of different between using Carbon or Metal Film... the carbons usually have a 5% tolerance and the Metal Film 1%... just more accurate when it comes to tolerances... Some people swear by the sound quality of the carbons over the metal film but my ears can't hear the difference. I don't know the specs of the UA741CN or how similar it is to the LM308... you can download the spec sheets for each and compare them. If you use an 8 pin chip socket on the board you can swap out the chips and test them easily. Aluminum foil as sheilding works ok... it is a bit difficult to get to stay correctly to the sides of the box without some spray adhesive. The best bet for something like that is Aluminum tape... you can get it at any hardware store for a few bucks. It is used for taping up duct work and is just thin aluminum with an adhesive backing... works great.

stevemilo (author)2010-04-21

 This looks great! I will be attempting this for a class. Just a question, though, how big is the circuit board? I have to design and cast my own case and I'm trying to get my numbers right. 

modernmusician1 (author)2010-03-18

This is really awesome! I will attempting this project within the next few weeks, I already ordered the parts from smallbear and it only cost me about 50 bucks for everything, and I actually came across the EXACT same case at my local electronics shop (which is cool, because I dig the color scheme!) Currently I have an original mid-80s proco RAT on loan from a very good friend, and after using it I just had to have my own. So hopefully I will have the original and the clone to test against each other before I have to give it back! This will be my first foray into electronics like this, so hopefully it all turns out alright! 

 Did your find all the Capacitors on small bear? I can only find two or three at best.

the capacitors were the only thing i had to buy at a local electronics shop. don't worry though, they're really cheap.

About This Instructable




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 »
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