Note: a wiring change has been implemented and foil coating has been added (05-28-13).
Added: source for momentary closed switch, heavy duty marine (boat) horn switch) , $9, free USA shipping
Seachoice Red Button Horn Switch
Demo video: http://youtu.be/9GWf2tjN_NM
For playing with acoustic guitars and non-permanently-mounted pickups, to reduce feedback, for playing on stage with multiple instruments, or for home recording.
This is a simple device for use when playing acoustic guitars with amplifiers and non-permanent or piezo pickup systems, to reduce/eliminate feedback, especially while the guitar is stationary or instrument cables are swapped. It silences the instrument for resting, or standing near vocal microphones without playing. It can also manually make a volume pedal or 'swell" effect (off/on only).
You can substitute materials for the box, such as a plastic junction box from the hardware store, with a plain outlet cover.
You can substitute the normally closed switch (auto kill switch) for a normally open switch, or a push-to-click off/on/off switch. A toggle switch can work, but is hard to use with shoes, unless the unit is velcroed to a pedal board.
You can use this for practicing/playing while seated at a computer, so you can talk on skype or put the guitar in a stand without noise/signal through the computer (recommend the off/on/off switch).
You can make this for a few dollars, maybe free, if you have an old guitar or amp to salvage for audio jacks, volume knob and potentiometer (dial), and a similar switch. You can use a plastic junction box and plain steel cover from a hardware store, made for electrical/lighting, or salvage one from home repairs/junk.
I recommend a heavy duty horn or starter switch that fits in your box and lies flat on the surface except for the protruding button, so you can step on it without being as delicate.
I used an inexpensive guitar cable to make the cable pieces (de-solder one end, cut what you need from a 10 foot cable, and re-solder to make a patch-cable. You can nick the outer insulation and strip it, then unwind the ground braided wire, leaving a dual-insulated inner wire). You can use a cord from a dead appliance such as a vacuum cleaner (carefully split the dual cable, and cut and strip to make your pieces).
If you need help soldering, please see other instructables or consult someone who works in a related field.
Step 1: Test installation. Mark and drill your box
I recommend copying the one I made, but you can make the cable jacks on opposite sides, on the narrow sides, or on the top if you wish. You can put the volume knob on the top if you wish.
Mark with a Sharpie, drill small pilot holes, and use correct bits for the items installed, such as 1/4" for the jacks. (test and drill smaller first if not sure).
Install components and close box, check for clearances to solder or run cables. You may have to solder items first, then install through the holes.
Pushbutton Normally-Closed Momentary Switch(4-Pack) $4
Model: 275-1548 | Catalog #: 275-1548
Project Enclosure (6x4x2") $3.50 (I used both lids together for strength)
Model: 270-1806 | Catalog #: 270-1806
1/4" mono Panel-Mount Audio Jack (2-Pack) $5.50
Model: 1/4" Open-frame open-circuit panel mount | Catalog #: 274-252
10K-Ohm Audio-Taper Potentiometer $3.50
Model: 271-1721 | Catalog #: 271-1721
Guitar cable, 10 feet, $5-10 at walmarts, guitar stores, music shops, pawn shops. Look for the kind with jack ends that you can unscrew and de-solder if you want to shorten the cable after removing some for wires. (you will need 2 cables to play your instrument through this box with an amplifier)
Step 2: Line box for shielding.
I used foil tape made for installing window units and plugging ducting leaks. It's $7 a roll and I had a lot left over after fixing the AC. It's like tin-foil but with a very sticky backing. Use small pieces, work from the bottom first and then the sides, using a couple layers where the pots or switches will be pushing through holes in project box. Be careful not to get paper cuts! It's wicked!
Step 3: Determine wire planning, and solder
I recommend soldering and testing the box with only the volume knob first, then adding the switch.
EDIT: I have added metal shielding (step 2) and re-uploaded a revised wiring diagram. This works very well and eliminates an error in my first upload. (sorry to any followers who got the errant diagram).
This one grounds the "tip" on the amp side, to the pot, and eliminates an un-necessary wire I had going between the 2 jacks.
This one is very quiet as intended. I have tested it in playing, unplugging guitar in cables, tested the pot, all very well now.
I recommend all guitar pedal effects or pre-amps go inline from the guitar TO the IN on the stop-box, for maximum silencing effect (any hum or buzz generated by or through your pedals will be killed by the stop box.
Thank you for your patience.
Step 4: Complete the box, mark for cable IN and volume 0-10 if wanted
I just drew a mark for Max Vol. , and wrote IN next to the Input cable jack.
You can customize your box with stickers, sharpie art, paint, duct tape, glitter paint, reflective tape, custom knob(s), etc.
Step 5: Plug and play
Plug in your gear and try it out.
Step 6: Enjoy your new equipment
I hope it adds a new dimension to your playing and is the envy of your friends. Thanks for reading my Instructables.