Step 1: Making the Pickup
1. Piezo Buzzer Element
2. about 1 foot of shielded audio cable
3. a 1/4" audio jack (that can be mounted on the guitar body)
4. a small amount of medium density foam. (just a couple square inches)
5. soldering iron, solder, wire strippers, hot glue gun, and hot glue
- The first step is to design and create your pickup. The heart of the pickup is a piezo buzzer element. You can find these for just a couple dollars at your local parts store. (Radio Shack) Sometimes the Piezo Buzzer packages don't have that much information on them, but you want to find things as close as possible to the information listed on the "Specs:" page. In other words, they are pretty cheap so go for a good one. Also note that you do not need a fully functional buzzer device... just the Piezo element.
- A word about Piezo Elements. Piezo elements are made from two conductors separated by a layer of piezo crystals. When a voltage is applied across the crystal layer, the crystals pull on one side and push on the other. This in turn bends the metal conductor layers. When a sinusoidal signal (audio) is applied, the conductors are pushed and pulled very quickly, creating sound waves. The beauty of the Piezo element is that it also can be applied reversely. If sound waves push and pull on the conductors, an electrical signal is created and can be output to an amplifier or recording device. This is exactly how we will use the Piezo Buzzer element in this project. It will be attached to the inside of the guitar body, and, as the body vibrates, the sound will be turned into an electric signal by the Piezo buzzer element.
- Now that you have the Piezo Buzzer, you need to carefully break it open and get out the piezo element. Be careful not to hurt the metal device inside. Bending the element may cause it to break or lose some of it's sensitivity.
- You are now ready to solder the device together. Strip the ends of the shielded audio cable. On one end connect the signal wire to the center of the Piezo element and the ground/shielding to the metal/brass surface of the piezo element. On the other end of the shielded wire, connect the signal wire to the signal tab on the 1/4" audio jack and connect the shielding to the ground tab.
- We have found that a small piece of medium density foam improves the performance of the pickup over a large number of frequencies.(If you are familiar with circuitry, feel free to experiment with combinations of capacitors and resistors to cut undesired frequencies) Cut a piece of foam the same size of your piezo element and about 3/8" tall. Place a large drop of hot glue on the back side of the piezo element (where the wires connect) and then press the foam on until the glue cools.
- Your piezo pickup device should now be ready to install. You may want to make sure it is working by plugging it into an amp and lightly tapping on it.
Step 2: Specifications:
Transducer Size: 1.1"
Audio Range: 106 dB
Noise Level less than -111 dB
Output: 1/4" Female Audio Jack
Wiring: High quality shielded audio cable
Installation Time: about 1 Hour
The first graph shows a guitar with my pickups installed vs. an Alvarez Yari 12 string (This guitar is a professional model and has individual pickups for each couplet of strings. That's 6 pickups in all), and a Fender Stratocaster. The Fender Strat. is included because it is known for its full vintage sound with professional pickups.
From the graph you can see that the Alvarez is the best due to its overall amplitude and trend. It does however seem to be somewhat inconsistant above 6.0kHz. The Fender electric guitar has a very smooth curve, but as you can see, the high frequency response is low and the overall amplitude is well below the Alvarez. The green curve shows the frequency response spectrum of my piezo-electric pickup installed on an inexpensive guitar. While the amplitude is slightly lower from .4 - 1.0kHz, it more than makes up for this by its great mid. and hi frequency amplitudes. It sounds great plugged-in and lets you turn up the amp pretty loud before giving any feedback.
The second graph shows the difference between our piezo pickup and a generic piezo pickup installed on a guitar.
The green curve on the top is my homemade pickup while the pink curve on the bottom is the spectrum of a generic piezo element. It can easily be seen that getting an element with good specifications is very important. The piezo element I chose has a fuller sound across the entire spectrum. Also notice that the generic pickup lacks smoothness.
This is why it is important to choose wisely from all of the parts at your local electronics store. Getting a piezo element with the specs above will help to get you on the curve we obtained from our pickup, making sure you get a full, rich sound every time you plug-in.
Step 3: Installation: Step #1
- 1 Piezo-electric transducer pickup. (The main part)
- 1 Electric drill.
- 1 3/8" drill bit. (Use a spade bit)
- 1 Roll of double-stick tape / or hot glue (recommended) / or sticky putty
- 1 Roll of masking tape.