Read Time 6 Minutes
Here’s another episode in the continuing saga that is the Guitar-Muse Pedal Board. We’ve covered woodworking, staining, electrical wiring, soldering and signal wiring. Now, we’re embarking on an adventure in electronics… what’s next? Ha Ha! The Evil Professor is never short of ideas! Ha Ha Ha!
We’ll be working from Craig Anderton’s book, Electronic Projects for Musicians. This is a great book, but a little dated as it was copyrighted in 1975. Some of the components Craig specifies in the book are no longer available, and I’ve looked for them. There are some useful projects, though, given an ability to adapt the circuits 38 years forward. Here’s to Craig for providing a work that’s still going strong. The book is available from several sources online, Amplified Parts being one of them at AmplifiedParts.com.
I buy my parts from Jameco Electronics online Jameco.com) because I like their service and prices. You can try Mouser Electronics (Mouser.com) Radio Shack or a local electronics parts house. None of the parts are super critical except the 7809, our 9VDC regulator, but any 9VDC regulator will work as long as it works with a 12VDC input. Any diodes similar to the 1N4001 will work fine. The 1000uf filter cap could be a 12vdc model, but they are the same price as the 25vdc one that Craig spec’ed in his book, so I used it. The Tantalum cap needs to tolerate 10vdc or more. The small tantalum caps are polarized as well. The printing on this one is so small you’ll need a magnifying glass to see it.
Here is the parts list with Jameco numbers included:
You’re going to need a couple of other things, also, but your local Radio Shack would be good for those. Some 20 or 22ga hookup wire, solid or stranded, and a tube of Heat Sink Compound, to promote good heat transfer from the regulator to the heat sink.
I bought a 12VDC power supply (wall wart) from Jameco as well, but you can find these just about anywhere, now. Check your junk drawer first! I had several of these but tossed them some time ago. (“I’ll never need these things.”) Just make sure yours will provide 500ma (500 milliamps) at a minimum. The more ma’s, the more pedals you can power. The regulator does about 2 amps, enough for a dozen or more pedals, but your wall wart has to provide 2000ma or you’ll overload it.
The six, 5.5mm plugs are the plugs used to power the standard pedal and Radio Shack does not have them. The two male power plugs are to allow you to plug the wall wart into the regulator circuit, and your pedal power wires into the other end of the circuit.. If you would rather solder them in, you don’t need these either. The 2 capacitors, the diodes, the regulator and the heat sink are all required components.
Let’s Get Started
Figure 1 shows the schematic of our little regulator circuit. There are only 5 components, 2 diodes, 2 capacitors and the IC regulator.
The two caps are filters, used to insure we eliminate hum from the input and output lines. D1 is to protect the IC in case the 12 volt supply drops below 9 volts (an overload condition) and D2 will shunt any reverse polarity to ground to protect the IC once again.
Our 12VDC wall wart connects to the inputs on the left, either soldered in or through a plug/socket. Our output, on the right, connects to our plug chain for the pedals. Here, we reverse our connections and attach the ground to the center socket and our 9VDC to the sleeve, the standard pedal hookup scheme.
Two of the items in figure 2 make sense, but you may be wondering about the storage box partition. Rather than buy some perfboard or terminal strips for $6.00, we’re going to make our own for free.
So we’re going to mount the components in figure 4…
… onto the plastic piece from figure 3, and stuff it all away in figure 5!
The reason I like an Altoids tin for this is that it’s metal. If we bolt the heat sink right to the tin, it will really help with the heat dissipation, something a plastic container can’t do.
Figure 5.5 shows the component layout for the plastic partition. Note the polarity of the capacitors ( the + sign) and the diodes (- denotes the striped (cathode) end).
On IC1, pin 1 is input, pin 2 is ground and pin 3 is output. From the front, the plastic side, the pins are labeled from left to right.
Figure 6 shows the layout on the plastic.
Figure 7 shows the holes for the component pins.
The whole ball of wax fits nicely into the tin. Note that the IC is placed below the plastic and the pins are bent to come up through the plastic so the IC can be bolted down through the heat sink onto the tin.
We need a method for getting our 12VDC in and our 9VDC out of the tin. Figure 9 shows how I did it. I decided to use a metal jack that I had on hand for my input because the 12v power supply is center positive. That will put the ground (sleeve) to the tin through the jack.
For output, I robbed a battery eliminator from my box and used it for the female plug that’s on the end.
You can see in figure 10 that the IC’s pins are coming through the plastic from the bottom.
The wiring in figure 11 is the 18ga speaker wire again. It is a little larger than required but I had it on hand. I tend not to rush out and buy stuff if I can make do with something I have. If you use this wire, which is pretty inexpensive and available at Walmart, beware the soft insulation. It melts like mad!
Figure 12 shows the input and output wires to the “circuit board”. We’ll cut them off, strip the ends, tin and solder on our input and output wiring.
Figure 13 is the finished board, wired up and ready for test. If you look closely at the end of the input jack you can barely make out that I had to bend two pins over on the heat sink to clear the jack. I didn’t leave quite enough room for clearance and, even though I think it would have been okay, I played it safe and bent the pins over. Also, put a layer of electrical tape in the bottom of the tin to prevent shorts. (the dark shape in fig 13)
Yea! A perfect test… the second time. My first test smoked C2 and I’m not sure whether it was because I had the cap too close to the top (the tin’s lid was closed) or it was in backwards. Those little tantalum caps are really hard to read but you must polarize C2 in the right direction or you will fry it.
Figure 15 shows the plugs. They wire like any normal plug.
My only complaint with these is the covers are tough to get on and the lack of a good strain relief. I have found some better ones, though and I will be getting them next time.
Figure 17 shows the daisy chain plug, with a wire in and a wire out to the next plug. The strain relief is just a tad small for this but it works if you’re patient.
My short little daisy chain plugs are shown in figure 18. This gives me enough for 2 pedals, which is probably all I’ll ever need for open mic night. If I need a third pedal, I’ll just add another plug.
Figure 19 shows the finished product. My mother-in-law thought it was “So cute!” I kind of like the Altoids tin look.
I forgot to mention my grommet. I made it from the plastic sleeve on the typical solderless terminal strip lug.
Figure 21 shows the lug I used for my wire size but you may need a red or yellow one for yours.
If you damage the sleeve removing it, just try another. Then size the hole to fit the plastic sleeve and clamp it in place with a clip like mine or bend up a small metal strap. You can use the zip ties with the screw down hole, too.
Well, that’s it, you guys. Go to the forum Q&A if you need some help. I check in there every day. Please let me know how you’re doing on your board and post pictures. We would love to hear from you. I especially would like to know what other mods you have come up with on your own.