By Rowan Corbett
Assistant Manager and Guitar Stock Manager

It's inevitable that any performing acoustic guitarist will have to consider amplification, but the glut of options can make it hard to find the right setup for your situation. The goal of this series article is to shed some light on the various aspects of acoustic amplification. The information presented here is mostly intended for guitarists, but much of it can be adapted to other acoustic instruments. This particular article will cover the differences between the common pickup types, how they compare to microphones, and the strengths and weaknesses of them all.

Microphones were the only viable option for acoustic sound until the early 1980's, and in most cases they are still the best choice when sound quality is mission-critical. For the studio, condenser mics are the typical choice, though a high-end dynamic mic can be quite effective. For live performance, Shure's SM57 dynamic mic is the old standby, offering a good solid sound with fairly decent frequency response. But a microphone usually needs to be mounted on a stand, meaning the guitar must remain stationary. And at louder volumes, microphones are prone to feedback. On the other hand, an internal pickup allows the guitarist to move as far as her cable or wireless system will go. Also, when installed properly, most of the currently available acoustic pickups are more resistant to feedback than microphones.

Pickups

Under-The-Saddle
Undersaddle pickups are the most commonly found factory installed acoustic guitar pickups, and offer some of the best all-around performance. As the name suggests, they sit between the saddle and the bridge.

The pickup element uses piezo crystals (piezo from the Greek word piezein for "to squeeze"). When pressure is applied to these crystals they produce a small electrical current. In a pickup, these crystals turn the vibrational pressure into electrical current, which an amplifier can turn into sound

Because these pickups don't take vibration directly from the top, they are highly feedback resistant. But this means that you're mostly amplifying the sound of the strings rather than the guitar the pickup is installed in. This makes them ideal for high volume environments, but less than optimal when one desires a transparent representation of a particular guitars tone.

Installation of this type of pickup requires a small hole be drilled through the bridge and top of the guitar for wiring, as well as widening the endpin hole to accommodate a 1/4" jack.

Soundboard Transducer
This style of pickup, also based on piezo technology, takes vibrations directly from the guitar's top and often gives a more accurate representation of the instrument's natural tone than other types of pickups. The downside is that they tend to be much more likely to feedback than undersaddle or magnetic pickups, so high volume sound settings are usually not recommended.

Soundboard transducers are fairly non-invasive to the guitar, needing only the installation of an endpin jack. The pickup itself is mounted on the underside of the bridge with an adhesive, putty or double-sided tape.

It is possible to temporarily mount one of these to the outside of the guitar using the same technique above, adding a female 1/4 jack to the end of the cable instead of an endpin jack. This means the instrument can be amplified with no permanent alteration to the guitar, but the trailing cable often causes noise as the guitar shifts during performance.

Soundhole or Magnetic
Technically, this is the oldest style of acoustic pickup as it is essentially the same basic design found in electric guitars. They consist of one or more magnets wound in copper wire. Placed in the soundhole, the strings of the guitar pass through the pickup's magnetic field. When the strings vibrate, the pickup turns the disruption into an audio signal.

These pickups are the least susceptible to feedback and the easiest to install. They require only an endpin jack and are usually mounted in the soundhole with some form of padded, screw-adjusted clamp. On higher-end models, there will be individually adjustable pole pieces for each string. This is because the plain strings can be much louder than the wound strings.

Though easy to install and highly feedback-proof, these have the least accurate sound of any of the pickups described here. Because the sound is derived directly from the strings interaction with the magnetic field, the acoustic properties of the guitar or the strings never come into play. So if you want a pickup that more closely represents your guitar, you should choose a soundboard transducer or an undersaddle pickup.

Usually, these can be installed with little impact on the instrument. A hole for the endpin is required but the pickup itself usually clamps in place and has foam pads to protect the guitars finish. Again, these can be mounted with no alteration to the guitar by trailing the cable out of the soundhole. But unlike the soundboard transducer, they tend to produce little to no noise when jostling the cable.