A synthstick is a fairly simple electronic musical instrument to build. These instructions are based on similar ones found on folkurban.com. My design differs from that shown on folkurban.com in that I use metallic ribbon rather than Mylar. As it happens, it took a few tries and considerable frustration before I made a working synthstick. The use of a solderless breadboard, aka Experimenter’s Socket, made all the difference. I suggest building your first synthstick with such a socket so you have an idea how one can be set up. Then you can move on to building other such instruments using soldered boards (or Perfboards, if you will). You can also build variations of the synthstick circuit, including “weird sound generators,” such as those found on another website, “musicfromouterspace.com.” So far, I have been unable to duplicate any circuit shown on the latter website but have been successful in building similar devices using the synthstick circuit as a starting point.
Materials needed
Solderless breadboard
Integrated circuit: Hex Schmidt Trigger (aka CD40106)
10 mF electrolytic capacitor
Various capacitors from 0.1 to 1.0 mF. Polyester or ceramic okay.
¼ inch output jack
Volume control knob (linear taper potentiometer also okay)
9 Volt battery clip
mylar film. If mylar is not available, metallic ribbon or giftwrap will suffice. The best material is shiny on one or both sides. The shiny side is the conductive one.
VHS tape
Foam tape
Two-sided tape
Multimeter
Wire (single strand, copper core, 20 gauge is probably best for the purpose)
Piece of lumber: this can be a piece of scrapwood but a 2x4, about 21 inches long by 1 ½”x3/4” is good too. I’ve bought 2x4x48 lumber from the local Home Depot and cut the wood to length.
Two small screws, about half an inch long apiece
Two metal washers
For permanent synthsticks and variations (circuits mounted on perfboards):
One perfboard: 2”x3” (Radio Shack carries them)
Soldering iron
Rosin-core solder
14 pin DIP IC socket
Optional:transistors: PNP and NPN
Zener diodes
Assorted potentiometers
Assorted resistors
LEDs
A 2”x3” solderless breadboard to good to start with since the circuit itself is small. Make sure the board is upright, so the printed letters run up and down on the left side. Carefully insert the Hex Schmidt Trigger (CD 40106) into the socket, making sure the notch faces left and the chip itself straddles the groove in the middle. Be sure the IC is inserted properly and no pins are bent or broken. You might want to use the bottom of a ballpoint pen or eraser end of a pencil to gently press the IC into position.
The IC pins are numbered 1 to 14, with 1 and 14 facing one another and each being closest to the notch. Insert a capacitor, between 0.1 and 1.0 mF, into the breadboard at pin 1 in such a way the capacitor is perpendicular to the IC.
Insert a 10 mF electrolytic capacitor at Pin 4. Be sure the negative, “stripe” side faces away from the IC. Please note: I’ve tried electrolytic capacitors of various capacitance, both less than and more than 10 mF and found the 10 mF to be the optimum capacitance for the purpose.
Connect a quarter inch jack to a volume control knob with single-strand wire. Then connect the black wire of a nine volt battery clip to one of the free pins on the jack.
Connect the red wire on the battery clip to Pin 14. If need be, use a soldering iron to tin the black and red wires before inserting them in the breadboard. Another method is connecting these leads to jumper wires, if they are available. If you have jumper wires made for solderless breadboard, making connections is that much easier to accomplish.
Now you’ll need to prepare the stick part of the synthstick circuit. The stick part is a sort of variable resistor, consisting of VHS tape and either Mylar film or metallic ribbon, depending on what is available. Start with a piece of scrap wood or a 2x4. The latter will very likely measure 3/4x1 ½ inches. The actual length is up to you. Two of my synthsticks include 2x4s that are about 21 inches long in keeping with the length suggested in folkurban.com. Drill two holes, one on top of the wood, about half an inch from one end and the other at the very end, in the center right. Anchor two washers down, using two screws. Don’t tighten the screws yet. You’ll be attaching wires to them.
Use two-sided tape to fasten VHS tape to the stick, on the top left side. Be sure to cover the end of the stick, where you drilled the hole at the center right. This will be point A, corresponding to Pin 1 on the IC, in keeping with the directions on folkurban.com. You might want to use a pin or small nail to make the hole in the two sided tape, as well as the VHS tape.
Use the two-sided foam tape to mount the Mylar or metallic ribbon to the stick. Make sure the shiny (conductive) part faces down! This is the part that will be in contact with the VHS tape, not the dull side (if any). Start by applying the foam tape, parallel to the two-sided tape and VHS ribbon and as close to the latter as possible. The idea is for the Mylar or ribbon to cover the length of the stick, while leaving about 1/32 or 1/16 inch space between itself and the VHS tape. Poke small holes in the foam tape and Mylar or metallic ribbon in the spot where you drilled the second hole. Fasten the second screw, positioning the second washer between the Mylar/ribbon and the foam tape beneath it. The washer will need to be in contact with the metallic part, in this case. The second screw and washer correspond to Point B.
Strip the ends of two pieces of single-stranded wire (20 gauge, copper core okay). Crimp and attach one end of each to the screws and over the washers. Tighten each screw firmly. Connect the free lead from Point A to the second pin of the capacitor at Pin 1 of the IC and the lead from Point B to Pin 2.
That’s basically the basic Synthstick circuit. Test it out by snapping a nine-volt battery to the battery clip and hooking the circuit up to an amplifier by way of the output jack. At best, you’ll hear a sound that resembles a siren or something to that effect. Press down on the Mylar film or metallic ribbon so it makes contact with the VHS tape and note any variations in sound. As a way of trouble shooting, make sure all connections have been properly made. Some kinds of wire don’t fit solderless breadboards very well and you might want to use jumper wires as intermediaries.
When you are satisfied with the results of your synthstick, try variations of the circuit, using separate breadboards. Substitute a photocell for the variable resistor. Position the photocell (also known as a light dependent resistor) between Pins 1 and 2. Or add a potentiometer there, while keeping the capacitor in place. Try adding potentiometers to other pins as well and listen for any variations in sound. You can also add a filter, in the form of a LM741 to the circuit. Consider the usefulness of diodes (Zener, as well as Light emitting, or LEDs) and transistors (NPN and PNP). Here, I might mention a variation of the Synthstick, the Weird Sound Generator (WSG), or generators, as shown on musicfromouterspace.com.
Also, try different voltages with your synthstick. The Hex Schmidt Trigger can work well with a range of three to fifteen volts but especially with the nine volt battery. You might want to experiment with battery holders with two, three, four or six AA, AAA, C or D batteries. I prefer nine volts maximum, as a matter of precaution. Too much voltage can fry the Hex Schmidt Trigger, as well as present a dangerous hazard.
Also, a few of my circuits use no batteries whatsoever but rely totally on solar cells. No matter what arrangement of such cells I use, whatever combination adds up to nine volts seems to be optimum. Flexible or glass solar cells seem to work the best, especially those generating about three volts apiece.
To make synthsticks and other circuits that really last, you might want to consider building instruments from scratch, using perfboards and a soldering iron. If such is the case, you might want to consider fastening the IC to the board using an IC socket. Be sure to use a 14 pin DIP socket. Carefully solder the socket, rather than the IC itself, to the board, being sure not to create solder bridges between the pins. Speaking personally, only two or three of my synthsticks have ICs mounted on IC sockets. Most of the rest of my instruments with oscillator circuits have the ICs mounted to the perfboard with hot glue. In some cases, there is no perfboard at all. The entire circuit is mounted directly onto or into an Altoids container, as suggested in folkurban.com. Such practices might not benefit the respective ICs in the long run but the instruments seem to work quite well as is, so far. If you can successfully build circuits using available perfboards, or even better, build your own PCBs (Printed Circuit Boards) using etchant solution, so much the better.
For pictures, please go on to: http://jjbphotos.blogspot.com/
