This, my first Instructable, will show you how to add an external speaker jack to the infamous Pignose 7-100 battery powered amplifier. With this mod, you can use your Pignose to drive any size speaker, even a Marshall stack! If you love the sound of your little Piggy now, just wait until you hear it with large speakers.
I assume a basic understanding and ability to solder and drill sheet metal, but beyond that, this is pretty simple.
Step 1: Parts identification
You will need to purchase a mono switched phone jack, refer to the attached photo. This jack has three terminals, one for ground, one for the signal input, and one for the signal output. With nothing plugged in, the signal in and out terminals are connected together and the audio is sent to the Piggy's internal speaker. With a plug connected, the signal is routed to the external speaker instead of the internal Pignose speaker. This part is available from Mouser Electronics, p/n 161-MJ160M-EX
Step 2: Desolder the existing speaker wires
Remove all of the batteries from the Pignose. Carefully desolder the two wires from the speaker, refer to the photo. Note that the White wire is connected to the terminal marked with a red dot. We will consider this the positive (+) terminal. The other terminal is soldered to the shield of the wire, so this must be ground.
Step 3: Remove the amplifier cover
With the Pignose open, the amplifier Module is visible on the right hand half of the box. Remove the four small screws (indicated by arrows in the photo) and put them someplace safe. They are very small!
Remove the sheet metal chassis from the Pignose. You will need to drill a 3/8 inch hole in the top of the chassis.
Step 4: Install the Jack, and start wiring it up...
Drill the 3/8" hole.
You will need about 9 inches of two-conductor wire to connect the jack to the Pignose speaker. I used what I had on hand - some leftover car speaker wire - otherwise known as "zip cord" because the two wires can be split from each other like opening a zipper. Strip away about 1/4" of insulation from each wire. One of the wires in this pair was color coded with a red stripe, so I connected that to the speaker terminal with the red dot (the positive terminal). The black wire is connected from the ground, or negative terminal, of the speaker to the ground terminal of the jack.
Note that at this time, the white and shielded wires are not yet connected to anything.
Step 5: Connect the last two wires
You will need another piece of two conductor wire, about 6 inches or so. This will need to be spliced to the existing white and shielded wires. If your zip cord is color coded, use the red strip (or whatever color you used before) to connect to the white wire. Solder these together and wrap it with a layer or two of electrical tape.
Repeat this with the other wire, again wrapping the connection with electrical tape.
Now, connect the free end of the zip cord to the jack. The black wire connects to ground (along with the ground wire from the previous step) and connect the striped wire (positive) to the remaining terminal on the jack - the one that connects to the tip contact.
Step 6: All done - now test it!
Wiring is now complete! Make sure the jack nut is tightened down securely. Carefully install the sheet metal cover back in place using the four small screws. Insert the batteries, and test out the amp. With nothing plugged into the newly added jack, sound should come out of the Pignose speaker as usual.
Now open the amp case, and plug a 1/4" audio cord into the new jack. Plug the other end into an 8ohm speaker cabinet - any size - and try it out. Good luck, and enjoy.
The attached schematic diagram shows what we just did.