Design and Development Board Tutorial (Prototyping)

[jkokura]

So you've built a few pedals, perhaps from a kit or using a board from Madbean and your own parts, but you've always wanted more control over the circuit and don't know how to adjust it to sound like you want it to sound. Maybe you've spent some time reading online about how the parts in your pedals work together to shape and create the 'tone' of the pedal. Now you want to try your hand at taking a schematic and changing it a bit to tailor it to your own needs, or perhaps you even want to try taking a crack at designing your own circuit! But where to begin?

Building a Design and Development Board is a great way to start that process. It's a tool that will allow you to experiment with and make changes to circuits without having to commit them to a PCB in order to try them out. All you need is a schematic to work with and you can build the circuit, change the part values, and see what your changes can produce! It's a lot of fun changing the diodes, or the input filter capacitor and resistor, or even just experimenting with which IC to use. And that just scratches the surface! Using a Design and Development Board, you can see how changes to the schematic might affect your sound BEFORE you ever use solder. It's a great tool for trying out the two overdrives you're thinking about building - you can use this tool to build both of them and hear them through YOUR rig before you decide which to build.

Also, for those of you interested, this tool can also be used to double check whether your PCB's are working BEFORE you've boxed it up. Just like the Basic Testing Rig, the Design and Development Board can be used to "Rock it before you box it."

Please note: This tutorial is based on my own build, and this is just ONE way to build this kind of tool. There are many ways you can design your own, this is just a tutorial on how I built mine. Those of you who would like to build one can either base yours off mine or at least get ideas on how you can implement your own design. Also note that anything within *these* symbols pertains to a special part of my build that is not neccessary for a basic Design and Development Board. Just like with the Basic Testing Rig tutorial, you don't necessarily need to do things just the way I do, and I'll provide extra info on what I did and why I did it that way.

So where to begin? Let's start with a list of parts you'll need:
1x Wooden Board (A cutting board or other sheet of wood that is approximately 8"x12")
1x Bread Board (a plastic board used in prototyping)
1x Breakout Enclosure (I used a hammond box, taller and wider than a 1590B, but a 1590B will do fine)
1x Terminal strip (at LEAST 4 terminals will be needed)
1x DC Jack
2x Mono Jacks *3x if you want to include a headphone amp in yours like I did*
1x 3PDT switch (stomp or toggle, either works)
1x LED, Bezel, and CLR (4.7k 1/4 watt Metal Film works great for 5mm water clear LEDs)
1x Battery mount
Lots of wire of different colours in heavy enough gauges it will last a good long while. Don't use thin or easily broken wire because it will come back to haunt you later on!

Here are some pictures of some of the supplies I used!

A group shot of lots of the parts I needed:



The enclosure used for the breakout box:



The breadboard I used:



The terminal strip:



The extra bits:



*supplies for a headphone amp are not included in this list. I built one into my board so I didn't have to use an amp when I'm prototyping late at night or away from my guitar rig (i.e. in my garage).*
*supplies for an opamp splitter/buffer are not included in this list. I built one into my breakout box as well as the headphone amp so that my signal presented to the headphone amp and the amplifier after the breadboard would be a nice, clean, even low impedance signal.

Steps for building:

1. Gather up all of your supplies. Get everything you'll need and start to assemble them so that you can begin to envision how it'll all fit together. This is an important step, don't ignore it! You need to make sure your wooden mounting surface can easily accommodate the everything, you'll need to be sure where each part will mount on the board, and that the locations will work well for you when you begin to work on your projects, and you'll need to be sure that you have everything you need! You don't want to be scrambling to find that jack so that you can finish this, you will want to have it with you.

2. Decide on a layout that works for you and begin to mark your wooden mounting surface for any drilling you might need to do. I decided on a pretty simple layout that placed my breakout box on the left, and the breadboard on the right. I found a nice distance in between for my terminal strip and found I could easily mount my battery clip right there in between as well. I also found where I wanted my knob for my headphone amp as well as an approximate place for my LED and switch locations. Here's my approximate layout:



I ended up needing to make some adjustments to the Breadboard, and I needed to drill holes to mount the breakout box to the board. Details about both of those things are below.

3. Start to work on the breakout box enclosure. Only drill after some very careful consideration, measuring, marking, remeasuring and remarking, and then some more consideration. The worst thing in the world is to start drilling away and then finding out that you drilled a hole to far one direction or another, and now things don't fit right! Once you're sure, drill the enclosure just like you would any other pedal enclosure.

For my build, I decided to drill the enclosure with the 1/4" jacks for in and out on the left side, the DC Jack on the top, and the switch for bypass about the middle of the enclosure 1" from the bottom with the LED bezel right above that. I also made sure to drill a hole on the right side that would fit the wires I was using to connect to my terminal strip. It's important to note that you will need to drill a hole for at least 4 wires: Input, Output, 9V, and Ground. I used the wire I was intending to use to test and MAKE SURE it would fit in the hole properly BEFORE i had finished drilling.

As a side note, I do the same with Pots, Bezels, Switches and Jacks - I always bring them with me to the drill press or have them handy while I'm drilling. I always drill smaller holes and then up the size of the bit to the make a snug fit for the part. I always check to make sure that the part I need to fit in the hole WILL fit in the hole WHILE I'm drilling. It sucks to have stuff almost completely installed in an enclosure, only to learn that a pot's hole is to small and you need to remove everything to drill the hole larger.

*I drilled an extra hole for the output from the headphone amp, as well as for the Volume knob for the headphone amp. If you are making some sort of modification from the basic design, make sure you think ahead and plan accordingly. Take ALL your parts and make sure they'll fit in the box*

4. Once everything is drilled up, it's time to begin the wiring! Unlike with a pedal, all the wiring is done from the switch out. You don't have a PCB to worry about, the only thing you need to worry about is the wiring. Fortunately, the wiring for this breakout is JUST like wiring for any pedal!

Here's a link to the type of bypass wiring I use: Gaussmarkov Bypass wiring. The jack on the left is in, the jack on the right is out. The white wire is your bypass wire, in on the left middle lug of the switch, bypass through the lower white wire, then out through the middle lug on the right. The BLUE wire in the top left lug goes to the INPUT of the PCB/Breadboard, the YELLOW wire is the OUTPUT from the PCB/Breadboard. The Green wire in the Middle lug of the middle row is the ground. The short diagonal wire connects the input to ground when not in use, and the other green wire connects to the LED to indicate the effect/breadboard is in use. I use that wiring for two reasons: a) it's logical to me. The signal goes in one side, down and over in bypass, and then out the other side, OR it goes in one side, up and through the circuit, and then out the other side. And b) it grounds the input to the PCB/Breadboard when not in use.

For alternate wiring diagrams, use any described here: Bypass wiring. Essentially, you need to treat your input as the send to the breadboard, the output as the return from the breadboard, and the ground from the switch needs to connect to a jack's sleeve. You also need to install the DC Jack and connect to the LED using an appropriate current limiting resistor. The bypass is just the same.

Very important is how LONG to make your wires. Obviously, the input and output to the jacks only have to be long enough to connect to the those jack's lugs. Same with the ground on the switch and the connection to the LED. However, you need to make sure you cut your send and return to the breadboard at LEAST long enough to go out through the hole you drilled, and then connect to the terminal strip with some slack. I would say that 8-12" would generally be long enough, but it depends on your specifications. DO NOT make them too short. It is better to have them be too long and then cut them down rather than have them end up too short.

Obviously, you will also need to make sure you include a Power wire and a Ground wire connection to your Breadboard. Your LED and Power to the breadboard should connect to the same point, and the Ground can come from the sleeve lug of either of your jacks.

Finally, I recommend that you use a zip tie of some kind to secure all of the wires headed to the breadboard inside your enclosure in some way to provide strain relief. You can see in my image below that I did so. The zip tie was tightened around the wires but would knock up against the enclosure wall before the wire's solder connections were ever in danger of being abused.

Here's an image of me in the process of wiring up my toggle switch:



Here's an image of me in process with my wiring:



*Note that there's a few extra elements in mine. I included a Buffer/Splitter from the output of my switch. That buffer is secured directly 'below' the jacks. One output from the splitter goes to the direct out jack and the other output goes to the headphone amp secured on the left. The headphone amp is a project from GGG i built years ago and simply rehoused into this project. It's output is the stereo  jack because the headphone amp works in stereo. I used a mono jack for my input. The Buffered splitter is important in this instance because the output from the breadboard is being split, and we don't want the headphone amp to 'load down' the breadboard, we want them to be completely discrete from each other.*

Here's another pic of the breakout box fully wired up:



Mine is WAY more complicated than it needs to be. All it has to be is input and output jacks, a DC power jack, and a 3PDT switch with an LED indicator. That's it. I included extra stuff that you DON'T need to do, like a buffer and headphone amp. Don't worry about that stuff. If you want to include that kind of stuff, check the posts below for the more complex wiring diagrams.

5. Begin to mount everything to your wooden mounting surface. Notice that I said wooden. Wood is the best material to use in this instance because it is non-conducting, it is easily cut to size and shape, and it allows you to screw things into it's surface for easy mounting. You can use other materials, as long as it meets your requirements and works for you.

Here's an image of a solution I found for mounting my enclosure to the wooden surface:



I used a pencil and the enclosure's 'Lid' to mark out the four holes that the lid had. I then used a drill press to drill out a hole slightly larger than the bolt. I then used a drill bit that was slightly larger than the bolt head to counter sink the hole so that the bolt heads wouldn't intefere with the way the Design and Development Board sits on my desk. I then used bolts that were the same diameter and screw frequency but were 1 1/4" rather than the usual 1/2". I put them through the board and VOILA, I'm a genius! I was then able to secure the enclosure to the surface without fear of it moving or coming loose, because the bolts both held the lid to the enclosure as well as held the enclosure to the wood!

You can use other methods for securing your breakout box. Velcro is popular because it's easily come by for those of us that have pedal boards, and it's non permanent and easy to adjust. I didn't want this to come apart easily, so that's why I did what I did.

Here's how everything looked after this step was done:



The terminal strip and battery holder both were secured in using screws. Notice that the metal plate for the bread board has been cut. It was hanging off the edge slightly, so I used a hack saw to shorten it down. I then drilled holes so that the breadboard would be secured well. Screws hold the breadboard to the plate, and screws hold the plate to the wooden surface.

Also note those four wires coming out of the breakout box. Remember to mark them or colour code them in a way that makes sense for you. Because I was using different wire than I normally use, I only had two colours to work with which required me to mark the wires accordingly. I had to make sure I knew which was Ground, Power, In and Out.

6. Wire up the terminal strip. This is an easy step. You might be asking, "Why Terminal Strips? Why not just connect right into the breadboard?" Well, you could do that. It's entirely possible. HOWEVER, the wires that connect into the bread board will be unplugged and plugged back into the breadboard many times. Even though soldering up (tinning) the ends of the wires will help them last a while, you'll need to trim and re-solder them several times over the course of normal use. Eventually, you just won't have enough wire left to stretch onto your breadboard from your breakout box, and then you'll have to re-wire everything. Using a terminal strip will allow you to connect into your breakout box easily for many years to come!

Notice in my image below that I've marked out each terminal's function:



Thanks for taking a look, hopefully this is very helpful in your own process of learning and experimenting. Stay tuned for more tutorials on how to use these to experiment using great Madbean projects!

[jkokura]

Reserved

[jkokura]

Reserved

[redbean]

New to pedal-making, I recently found out about the Beavis Board, and decided I must get it somehow.

Sadly, it was discontinued.

So, thank you very much for this tutorial, Jacob! (there should be a 'you rock' smilie) This is on my to-do list after I get started with some beginner projects.

[bigmufffuzzwizz]

Great information! You rock man!

[blueguitone]

ty very much, i have been looking for a thread about this..............

[josetxu]

Really great!!! thanks for sharing!

[redbean]

Hi Jacob,

I am preparing to order supplies to build a prototyping board.

I'd like to know what supplies/parts you used so I can add a headphone amp and opamp splitters/buffers, like your prototyping board, in order to obtain a clean, low impedance signal (as well as the diagrams).

Also, I'd like to set up a stereo effects return to the headphone amp in order to test stereo effects in the future. The Tyco Electronics terminal block I am ordering will have additional one channel (5) for this purpose. What are your thoughts on this?

Thanks.

[culturejam]

I made a test rig that is somewhat similar to this. I had enclosure left over from an old project that already had the stomp switch, jacks, and LED/bezel, and it was perfect for testing. I just added one of those spring-loaded speaker hookup panels (instead of the screw terminals) for attaching in, out, gnd, and 9v.

[MattL]

Thanks a lot for this. I especially likes the "Mine is WAY more complicated than it needs to be. All it has to be is input and output jacks, a DC power jack, and a 3PDT switch with an LED indicator. That's it. I included extra stuff that you DON'T need to do, like a buffer and headphone amp. Don't worry about that stuff. If you want to include that kind of stuff, check the posts below for the more complex wiring diagrams"! I know there are many ways to wire the bypass switch. Will most suffice? I'd like to use the tonepad easy way, since I've got it memorized.

[bigmufffuzzwizz]

Madbean has a wiring document in the top right of the projects page.

[MattL]

Does this mean I CAN'T use the tonepad method? If so, why not?

[bigmufffuzzwizz]

Does this mean I CAN'T use the tonepad method? If so, why not?

I don't see why not unless someone told you differently. There's many verified working ways to wire a 3PDT for true bypass but they don't all ground the input when the pedal is in bypass mode. This helps to eliminate the pop when turning the effect on. I personally like Madbean wiring schem and it really is an easy way to include everything. If you save your component leads you can easily connect the lugs used for ground and where input enters lug 4 to 9. But its DIY so do it your way!!!

[jkokura]

Yes, the Tonepad method is just fine.

I think there are four popular methods of true bypass. All of them are viable and interchangable. None is really better than another, unless you need or don't need the input grounded, as not all do. However, I just do the one that I'm familiar with and feels comfortable. The Gaussmarkov method is great.

Jacob

[sgmezei]

at CultureJam

Can I ask what the cap on the speaker hookups is?

at Jacob
I really enjoyed this tutorial and am in the process. Thank you for your help. Also, do you use a little speaker for the headphone amp or just the headphones?

Great thread and a big help.