If you’re new to electric guitar or bass, you’ll run across all kinds of instrument-related terminology you probably aren’t yet familiar with. Two terms you’re bound to encounter when researching a purchase, for example, are passive and active electronics. When shopping around, you’ll want to understand the difference between a passive instrument and an active one. While it might sound highly technical, the basics of passive and active electronics are actually quite easily understood even if you don’t have a degree in electrical engineering.
Among electric guitars and basses, passive electronics is the simplest and most common design. A passive instrument is one that does not have its own onboard amplification circuitry, and its electronics can only subtract elements from a signal. As such, the pickups on these instruments do not have their own onboard power source (such as a preamp) and the controls can not amplify a signal; they can only cut or filter a signal.
The pickups on passive guitars and basses consist at the most basic level of a magnet wrapped in coils of wire. In the magnetic field produced by this design, a vibrating string produces a weak electrical signal. This weak signal is sent through your instrument cable to your amp, which is where all the signal boosting happens.
Passive electronics are thus pretty straightforward, and it’s usually easy to tell passive guitars and basses on sight because they do not have battery compartments on the back of the body or elsewhere.
Most Fender instruments are passive. In fact, all Fender instruments were passive until the early 1980s, when active electronics were introduced on the short-lived Precision Special Bass model of 1980-1983 and the Elite series instruments of 1983-1985.
Guitars and basses that do have their own onboard amplification circuitry are said to be active instruments. Whereas passive electronics can only subtract elements from a signal, active electronics can both subtract and add elements to a signal. The pickups on these instruments do have their own onboard power source—usually a preamp itself powered by one or two 9-volt batteries—and the controls on these instruments can both cut and boost (amplify) a signal before it’s sent to the amp.
Active circuitry can provide functions in addition to signal boosting, including EQ, filtering, and feedback control, and it’s less susceptible to electrical interference than passive electronics. Because of the extra parts and circuitry, however, active instruments are more expensive than passive instruments. Active instruments are easy to identify on sight because they typically have a battery compartment somewhere on the instrument body; usually on the back.
Active circuitry is especially popular for bass guitars, making them brighter, clearer and snappier. The broader tonal range makes active basses especially popular for slap-and-pop playing. Active pickups are also popular on high-performance guitars often used by metal players.
It’s important to note that an active instrument will not work at all if its onboard power supply has been exhausted. That is, if the onboard battery is dead, an active instrument will cease functioning altogether; it will not continue to work in a passive manner. That’s why it’s important to have spare batteries, and that’s why it’s important to unplug active instruments when they’re not in use, because leaving a cable plugged into the instrument’s output jack drains battery power.