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 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.

Comments

[koroshjj]

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]

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]

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

[Goldswordfish]

..and the final budget to create this?

[silverHalo]

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]

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]

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 ... http://www.smallbearelec.com/servlet/Detail?no=1232

[babakkamiyab]

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

[bzalavári]

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

[silverHalo]

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

[macboy98]

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

[Lexoo93]

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

[EPIC Kelly]

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

[silverHalo]

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 all...it 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]

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]

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]

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

[silverHalo]

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

[deco97]

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

[icanmunch]

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]

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]

Hmmm, there are a few things that can go wrong. First, the AC power supply (9v 300mA) isn't actually 9v's....it'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....
Goodluck!

[aritoner]

 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]

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]

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.
thanks.

[silverHalo]

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]

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

[silverHalo]

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]

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

[silverHalo]

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

[lfebrero]

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]

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

[olivero1]

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]

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]

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]

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...

[silverHalo]

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]

 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]

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! 

[hacker3455]

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