Guitar Booster Pedal (MPX-1)

Every guitar player desires it:

The "perfect" sound!

The components for it are:

SOFT

• skill of the player
• mojo, soul, heart (name it the way you want, but essentially you can't buy it -> You have to have it!)

HARD

• the guitar (the wood, the strings,... -> The Hardware)
• for electric guitars: The amp/speaker unit

While we can't do anything but practice for the "soft" side we are able to improve a lot on the Hardware side without getting too much into expensive regions while doing it all by ourselves. This is the point where the hardware gets a little heart and soul ;-).

The easiest way to improve your sound into the desired direction is an effect, because you can modify the signal into the way you want it to be, without the need of cracking up your guitar of amp, which can result in broken and useless gear if you don't know what you're doing.

I started with a booster effect my brother wanted for his birthday, which is shown in the following steps. He mostly plays "Fender Strat Style" guitars with singlecoil pickups into a clean to lightly distorted amp. He wanted to add a little crunch to his tone without adding to much harsh distortion.

After choosing an effects type you should find a circuit that will give you your desired sound. Therefor you can use the web (search for example for "guitar", "effect", "schematic", "diy",...) or try to get your hands on literature about this topic. If you are skilled or you are just an optimistic tinkerer you might want to do it all by yourself and design your own circuit, which is totally fine/fun/challenging/rewarding/... but not appropriate if you are a beginner and have to search the web for every component value or formula for calculation of high-/ or lowpassfilters. (If you didn't get what a lowpassfilter is -> Stick with a design of the web that was proven to work)

For my booster pedal I chose a design of the web which I modified to get the desired sound. When you choose a design you might want to consider that your electronics dealer is not able to deliver you some parts you would need to build the circuit. Check that before you start building/buying/desiring your effect, because if highly required parts can't be supplied to you your project dies before it begins.

My Design (Schematic at the bottom)

I chose an overdrive pedal design off of generalguitargadets.com (Schematic) and modified it like this:

• added a simple positive/middle/negative supply

• added a noise filter I found on beavisaudio.com right after the DC Jack (Huminator)

• took away the clipping diodes on the output

• connected the diodes in the feedback path directly

• added the switch to change the resistance of the feedback path (10k <->30k)

Specifications:

• 5-6V DC from power supply or battery

• Standard gain of 11 (Preamp)

• Boosted gain of 31 ("Crunch")

• ON/(OFF) Switch + 1 Volume Poti

BOM (bill of materials)

For my booster pedal I chose the following components:

• Piece of perfboard 1,5"x1,5" (14x14 holes)
• 1/4W 5% Resistors (100,1k,1.5k,5x10k,2x100k,1M)
• Ceramic capacitors (2x47nF, 100nF, 10nF, 47pf)
• Electrolytic capacitors (2x10µF,100µF)
• 1/4" Mono Jack (6,3mm) 2x
• DC Jack (2,1mm Pin) 1x
• JCM 4558 OP-AMP 1x
• 8-Pin IC header 1x
• Mounted LED 1x
• DPDT Footswitch 1x

• 10kOhm Potentiometer + Poti knob 1x

• Hammond 1550B aluminum case 1x

• Wires to connect the jacks,poti,switch and LED with the board

Tools needed

• electric drill with metal drill bits
• screwdrivers
• soldering iron (a simple one should do the job)
• pliers
• wire cutter
• exacto knife
• wire stripper
• ... (equipment of your choice)

Don't ever start to build a pedal without breadboarding and evaluating if :

• the circuit works
• the effect is the desired

Otherwise you'll earn nothing but frustration.

To check the circuit for it's characteristics a multimeter for the power supply and an oscilloscope are highly recommended, because if you are able to see what the circuit does to your signal you are able to improve it much easier than through guessing.

If you tested your circuit and one of the above points failed you can easily add/change components until you are satisfied. When you are hearing a silent buzzing while testing rest assured: It will be gone when you assemble your board in a metal enclosure, because it shields all noises emitted of electronics hardware/FM/etc. which influence your circuit and result in the buzzing.

Always remember: You have to like it. If you like it -> It's great!

When you are satisfied with your effect you can solder it onto a piece of perfboard. If you are more experienced and want to create a layout to etch a unique board on your own feel free to do so. For beginners I would highly recommend a piece of perfboard.

The perfboard layout of my circuit is attached to one of the last steps with the schematic and the drill map.

It is recommended to put in the flat/small components first and go on with larger ones. I like to work along signal or power supply paths. Do it the way you want, but consider checking the components in a printed schematic if you soldered them in. This way you can easily see where you might have missed a part.

Always remember:

If you know what you need, you don't need to exchange expensive hardware parts you destroyed!

Think before you get into destruction mode.

Mark on your enclosure (because of noise shielding preferrably a metal one) where you want your jacks, potis,LEDs and switches to be and drill the holes.

Be sure to measure the diameter your components need right, because if the hole is too big the part will not fit in and your enclosure is damaged.

For drilling metal enclosures:

• use metal drill bits
• use lubricant (oil) to prevent the drill from getting too hot
• start with a small diameter bit(2-3mm) and expand the hole to the desired hole diameter

If you want to paint the enclosure you should clean it from every oil/fat and other components that could prevent the paint from sticking.

Use gloves, to prevent the enclosure from skin fat you always leave on things you touch with bare hands, and some cleaner (I use alcoholic wipes for glasses).

DON'T TOUCH THE ENCLOSURE WITH BARE HANDS UNTIL YOU ARE FINISHED PAINTING IT!

Put some tape from behind above the drill holes in the enclosure to prevent the paint from getting inside the box.

Use a primer for metal enclosures (mine had a grey color). Let it dry for at least 12 hours.

Use any spray colour you want to use (in my case a nice warm orange). Let it dry for at least 12 hours

Apply several coats if needed. Let them dry as mentioned before

Let each coat of paint dry for at least 12hours so that you can rest assured it won't peel of if you work on it later. I did it once -> it looked "interesting" but not as good as desired ;-)

Cut out and apply labels to spray them in a different color on your enclosure or draw them by hand. It's your enclosure play around a little until you think it's super cool (or just enough damage is done :) )

I tried to do it with clear adhesive tape but when I started to remove it after painting the labels it took all the coats of paint under it with it. The whole enclosure looked like a mess.

To achieve a better labeling I used overhead projector sheets on which I copied the labels and cut the letters out with a xacto knife.

Use a font like this one to make your life cutting the letters easier ;-)

Use painters tape to put the label templates on the enclosure and spray them with a color of your choice.

Let it dry for at least 12 hours.

Peel the label templates patiently off the enclosure and make use of some clear coating to prevent the paint from wearing to much (a bit is ok ... it looks vintage that way ;-) ).

Let it dry.

Put an insulating material into the enclosure to prevent shorts in the electronics. You can use simple painters tape or anything else that is sticky enough.

Apply some rubber/plastic/felt/... feet to avoid scratches on the floor (metal is harder than PVC or wood) and shifting the pedal when hitting it hard with your stompin' feet.

Plug in your guitar on the input, your amp on the output and rock out (or whatever your effect is supposed to do).