No matter what your gig, amplifying your favorite acoustic onstage can be a challenge. Several technological solutions are available, but the industry standard for over two decades has been the undersaddle piezo pickup. Larry Fishman, founder and president of Fishman Transducers, began experimenting with piezoelectric technology in the late ’70s, and although his company offers a full range of state-of-the-art acoustic products including pickups, preamps, amplifiers, and digital processors, we asked him for a basic piezo primer.
How exactly do piezo pickups work?
Piezo comes from the Greek word that means “to squeeze.” The pickup is made from material that reacts to vibration—traditionally this was hard ceramic but now many companies make them from polymers. An electrical charge is pumped down a wire proportional to the amount of pressure applied. This excites a preamplifier that is then run into an electrical amplifier. We placed the pickups where the most vibrational sound information is transferred: underneath the saddle. When people talk about piezo pickups they generally mean undersaddle pickups. An inexpensive transducer on the face of your guitar is technically a piezo, but for this discussion we’ll stick to undersaddle piezos.
What are the advantages and disadvantages of piezos?
They offer a reasonable facsimile of the vibrating string’s sound. On the downside, they miss a lot of resonance—the column of air from the soundhole creating a disturbance in front of the instrument gets lost. High-end condenser mics are most accurate for reproducing sound, but their onstage application is limited because you can’t turn them up very loud without feedback, there’s tremendous bleed-through, and the player is basically forced to stand still. In a controlled studio environment, condenser mics are the way to go, but live, the piezo is your savior.
Piezos are generally run in conjunction with a preamp, right?
Yeah. The days of running passive systems are long gone. That was 20 years ago, and if the console didn’t match the impedance of the pickup, it sounded awful. Piezos are capacitive devices and the sound changes dramatically with the input impedance of the amplifier you use—there’s no standard. A preamp is a small electronic interface that buffers the pickup from these variations and ensures full-frequency response. Our systems are active, powered by a 9-volt battery, and have an electronic preamp built into the cover of our endpin jacks.
Many preamps feature active tone and volume controls built into the guitar.
Right. You can shape the sound with a variety of controls like bass, treble, volume, and graphic EQ, designed specifically for the frequency range of an acoustic guitar. If you plugged a buffered system into a mixer, you’d have general-purpose controls for your channel but their frequency points are not really optimized for acoustic instruments. We build them into the upper bout of the guitar for convenience.
Doesn’t sticking a hunk of plastic in the side of your guitar diminish its overall acoustic properties?
I challenge anybody to prove that! The wood on the side of a guitar has little to do with the overall sound. You could argue that it might hurt the heirloom value, but as far as affecting the sound—don’t believe it. You could cut a hole in the side of a guitar and cover it with cardboard and tape and it would sound the same.
Is your current product development focused more on the preamp or the actual pickup?
We feel we’ve taken pickup technology as far as it can go for now. Most pickups on the market are of consistent quality—some sound brighter, others may have more bass response, so it’s just a matter of personal taste. But recently, we’ve introduced the Aura Acoustic Sound Imaging system, which enhances our basic pickup technology with sophisticated digital processing. Digital technology is definitely the next step.
