Acoustic 101

Amplifiers are an indispensable part of any electric guitarist's sound, as essential as the guitar itself. In comparison, acoustic guitarists often view amplifiers as a necessary evil, at best - and that's a huge mistake. Some amplification is almost a necessity if you need to be heard by more than just a few people, or need to perform with louder instruments (like drums). Amplifiers also offer a way to alter your tone and extend the possibilities of your instrument.

If you have an electric-guitar amplifier, you can use it for your acoustic, and you may be able to get a sound you like, but electric-guitar amps are often designed to color the sound, while acoustic amplifiers are designed to be as clean as possible, almost like a small PA. For example, it's not uncommon for acoustic amps to have a tweeter (much like a hi-fi speaker) to produce a wider range of frequencies, and they may also have built-in effects that are optimized for acoustic guitar. If you want to use one amp for both electric and acoustic guitar, you could use a clean, wide-range acoustic amplifier in combination with a modeling pre amp for your electric guitar. If you spend a little time learning how to use your amplifier, you'll get a better sound and enhance your performance.

Get to know the Ins and Outs:
An amp's inputs and outputs determine to some extent how it can be used, so that's a good place to start when shopping for an amplifier. Of course, every amp has an input jack for your guitar, but many amplifiers include multiple inputs that have other functions. A second channel can be used for a second guitar or to blend a stereo pickup. A three-pronged XLR input allows you to plug in a microphone, either for vocals or your guitar. Some amplifiers provide phantom power, which is needed by most condenser microphones. A few amps also offer low-level phantom power (usually 6 to 15 volts, rather than the normal 24-52 volts), which can be useful if your guitar includes an internal mic.

Your amplifier may have a line out or direct out. The former is a quarter-inch jack that provides an output suitable for driving an external power amplifier, a mixers line input, or a recording device. The direct out, which serves the same function as a DI box, is usually an XLR connection - the most common way to connect to a mixing board. Some amplifiers also include an output for an electronic tuner.

Tone Controls:
Most amplifiers have at least a volume control as well as bass and treble tone controls. Some may also have a midrange control. The frequency range affected by each tone control varies with different brands, so you'll need to experiment to learn how to best use them with your instrument. Try starting with the tone controls set to a middle position so you have room to adjust them in either direction. Some amplifiers, but not all, are designed to be "flat" (no EQ) with the tone controls in the 12 o'clock position. If you need to make adjustments, remember that you can use tone controls to reduce as well as boost different frequencies. For example, if your guitar sounds too thin, try cutting the treble instead of boosting the bass. If the guitar sounds too muddy, try cutting the midrange instead of boosting the treble.

Channel and Master Volume Controls:
Many amplifiers have a master-volume control in addition to volume controls for each channel. While the master and channel controls affect the amplifiers volume, the channel volume also affects the tone. What you want to do is find the peak clean setting of the individual channel volume, and then use the master volume to control the overall volume. Here's one way to find the proper settings for each: Turn the master volume all the way down, plug your guitar in, and play as hard as you can. If your amplifier has a clipping indicator, slowly increase the channel volume until the light flashes occasionally, then turn it down slightly. If your amplifier has no clipping indicator, turn the master volume up just enough to hear the sound and listen for the distortion as you increase the channel volume. When it starts to distort a little, ease it back a tad, then use the master to control the overall volume.

Notch out Feedback:
Many amplifiers have a notch filter, which can help control feedback by "notching out" (eliminating) the frequency that's causing the squealing. To find the right setting for the notch filter, slowly turn up the amplifier until feedback starts (be careful to do this gradually so you don't hurt your ears). Then adjust the notch filter's frequency until the feedback disappears. The frequency at which the feedback occurs will depend on the room, the guitar, and even where you are standing, so you may need to readjust this in different venues. Some amplifiers also have a phase switch, which can help with feedback. If you're having trouble, simply flip this switch to see which setting works best. And don't forget that you can always fight feedback by reducing the volume.

Effects Color your sound:
Reverb, which is included on most acoustic amplifiers, can help restore some of the ambiance that gets lost when amplifying an acoustic guitar. Other effects, like chorus and delay, are included on some amps, and can be used to alter your sound even more dramatically.

Besides built-in effects, many amplifiers have an effects loop: a pair of jacks on the back of the amplifier that allows you to add effects between the amp's preamped signal and its power amp. To use this, run a line from the effects-loop output into the effect box's input, and then from the processor's output back into the effects-loop input. Effects loops usually work best with rack mount effects units that are intended for line-level inputs and outputs. If you want to use stomp boxes, simply plug them in between your guitar and amplifier.

Find the Right Spot for your amp:
When performing it's important to find the right location for your amplifier. Besides fitting into the available space, you need to make sure the sound is right for the audience, as well as yourself and anyone you're performing with. You can reduce the chance of feedback by pointing the amplifier away from your guitar. If you connect your amplifier's direct out to a PA system, you can use your amplifier as a stage monitor, which allows more flexibility in placement and volume. You can choose a location and volume level that allows you, as well as any band mates, to hear comfortably, even if that means the amplifier isn't pointed toward the audience. In more modest venues, you'll need to experiment to find a location that works for everyone. Try starting with the amp off to one side, aimed at the audience, but angled slightly toward you.

Practice with your Amp:
Just as you practice your instrument, you should also spend some time practicing with your amplifier so that you get used to the sound and understand how to adjust the controls. Your amp will sound a little different in every room you perform in, but if you take the time to explore your amplifier's features and get to know how each control affects the sound, your sound checks and performances will go more smoothly.