Amp Terminology

Cabinet
Often made of plywood or particleboard, a cabinet houses the circuitry and often the speaker of an amplifier. It is usually covered in a protective material such as Tolex (rubber) or vinyl, or even carpeting.

Compression
An effect in which no matter whether you play loud or soft, the notes are heard at approximately the same volume because their dynamic range is compressed by the circuitry.

Corners
Protective metal or plastic that fits over the corners of the cabinet and keeps the particleboard or plywood from being damaged.

Distortion
When any part of the amp's circuit is given too much signal, it distorts. The sound you hear is fuzzy and grating and is referred to as distortion.

Feedback
The ringing or howling sound when you put a guitar, bass, or microphone too close to an amplifier's speaker. The sound is amplified, picked up again by the instrument, amplified again, and so on, until it builds up enough to make a noisy scream.

Gain
As you might expect, this is an increase in signal levels. Most amps give you a control for managing this.

Gain Knob
This knob sets the input signal level from an instrument. Guitarists often use it to add distortion by overloading the circuits after the input gain.

Grille Cloth
Though it looks like ordinary fabric, the cloth over the front of an amplifier is tough and protects the speaker from being damaged.

Handle
Like the handle on a suitcase, this makes it easy to carry an amp. Some handles are recessed into the cabinet's sides.

Input Jack
Here's where you plug in the cord from your instrument. This is usually a 1/4" jack.

Impedance
This is the tricky mixture of frequency and resistance (for you tech types) that determines whether such things as the output of an amp is suitable for the input of a speaker. If the impedance values of the two pieces of gear match, then you get the best volume and efficiency. If the impedance values don't match, then you can harm the amp or the speaker, and the efficiency drops.

On/off Light
Here's a hard one.

On/off Switch
If you can't guess this one, then guitar might be a bit tricky.

Overdrive
When the signal from the input stage is higher than the circuit after it can handle, it distorts in a way that's known as overdrive. This is what gives rock guitar so much crunch.

Speaker
Everything your amp does to make your instrument louder has to go through the speaker, which is made of a tough paper or plastic cone with a coil attached and a magnet inside the coil. Electrical signals from an amp pass through the coil, cause the speaker to vibrate, and sound is created.

Standby Switch
This is often found on tube amps. Instead of turning the amp off between sets, a player can set it to standby, which keeps the tubes warm and ready to go as soon as the switch is flipped to its run position.

Tone Knobs
Some amps just have one tone knob, which lets you remove brightness, or more tone knobs that let you shape the tone in a more sophisticated way. Some amps even have a graphic equalizer, which has several slide controls for boosting or cutting certain bands of frequencies.

Tube
Called a vacuum tube (or in England, a valve), it looks sort of like a strange light bulb, but it's actually vital to amplifying signals in an amplifier.

Volume Knob
Some amps have a single volume knob that sets overall loudness. It's simple, and it works.

Wattage
The output power of an amp is expressed as watts. A small amp usually has 10 or 15 watts, and the ones that the Red Hot Chili Peppers use have more than 100 watts each. Assuming that the speakers can take all that power, the higher the wattage, the louder the amp/speaker combination.