Buying Guide:DJ Equipment Part 6 - Glossary
1/4" connector: also known as phone plug. Unbalanced connection using a phone-patching cord
Anti-skate: counteracts the tone arm’s tendency to pull toward the center of the record. Anti-skating controls adjust to match your cartridge’s recommended setting
Balanced: a three-wire cord that provides noise-free transfer of audio in areas susceptible to electronic interference, like recording studios and live sound venues
Beatmatching: also known as beatmixing. Matching up the beats of two tracks so they play simultaneously in order to create a new track or seamlessly transition from one track to another
Belt-drive: inexpensive turntable design that usually has a motor below and to the side of the platter and drives the platter via a rubber belt
BPM: beats per minute. Measured by counting the number of beats in 60 seconds. Determines the pace or tempo of the music—for example, hip-hop will have a lower BPM (slower tempo) than jungle.
Cartridge: converts the mechanical energy of the stylus to an electronic signal. Can be identified by its four metal prongs
Channel: a single path of audio through a mixer, processor array, recording device, or computer interface
Clipping: distortion due to an overdriven preamplifier or amplifier
Counterweight: located at the opposite end of the tone arm from the cartridge, it adjusts the amount of tracking force pressure exerted by the stylus on the record.
dB/Decibel: a logarithm that describes the ratio of two powers (1/10th of a Bel). Some approximate reference points: a normal conversation has a decibel level of 60dB, a ringing telephone is 80dB, shouting in the ear is 110dB, and a jet engine during takeoff is 150dB.
Direct-drive: turntable design in which the motor is located directly below the center of the platter, producing higher torque and allowing the platter to achieve full speed in less time.
EQ: short for equalization or equalizer. Usually refers to a circuit that provides control over the frequency response of an audio signal that passes through it. Can be used to balance frequencies for more pleasing sound and reduce undesirable frequencies.
Fader: a sliding lever that typically adjusts levels. Has the same function as knob-based controls but provides a smoother response, more fine-tuned control, and visual feedback for quickly determining level.
Frequency response: a measure of output amplitude (level or loudness) over a specific frequency range. Simply put, this is the frequency range (or bandwidth) that the unit will pass without severe decrease (attenuation) in amplitude. It is measured in dB and will usually be presented as follows: Frequency Response: +0/-1dB @ 35Hz - 20kHz. This means that there is no more than a deviation in level of -1dB from 35Hz to 20,000Hz, while frequencies above and below that range will be attenuated severely. Increases in amplitude are not discussed in the case of properly designed solid-state devices, since they are the sign of an unstable unit. Tube designs with output transformers will show an increase in amplitude. Even though frequency response is an objective measurement of a unit’s performance, it cannot predict sound quality.
Frequency band: portion of the frequency spectrum, e.g., bass, treble, midrange
Headphones: pair of miniature drivers (speakers) designed to be worn on the head for monitoring audio material. Headphones come in closed, open, and semi-open designs. Closed headphones seal the ear off from outside noise for better isolation and are ideal for monitoring during performances and playback. Open headphones sit on the outside of the ear but don’t seal it from exterior noises or the acoustics of the room. Semi-open headphones seal the ear, but usually have a semi-open ear cup, which allows the audio to interact with the acoustics of the room more naturally while still providing some isolation.
ID3: stores information about an MP3 file in the MP3 file itself, usually the song title, artist, album, year, comment, and genre
Level: the amplitude/strength of a signal
Monitor: speaker specially designed for high-fidelity playback of audio material. Varieties include near-field, surround, active, and passive. Near-field monitors are designed to be used in very close proximity to the listener to limit interference from the room acoustics. Surround monitoring arrays use all the normal speakers included in a typical 5.1 setup. Active monitors have built-in power amplifiers that eliminate the need for a traditional, separate amplifier component. Passive monitors are traditional speakers that require an external power amplifier.
Noise Floor: Usually measured in dBV or dBu, this spec is an absolute measure of the mixer’s noise. A mixer with a lower noise floor will be quieter than a mixer with a higher noise floor, hence a lower dB rating is better.
Phone plug: also known as 1/4" connector. Unbalanced connection using a phone-patching cord connector. The most basic connection in audio.
Phono plug: the more correct name for an RCA plug. This connection was developed and popularized by the RCA corporation in use with their audio equipment, resulting in it being called RCA. Most often used in stereo pairs.
Pitch control (also called pitch bend): allows you to adjust the speed of playback in order to beatmatch one record to another. It’s called a pitch control instead of a speed control because as you change the speed of music, the pitch also changes.
Power amplifier: Basically there are two types of amplification: the voltage amplifier, which boosts voltage, and the current amplifier, which increases current. The power amplifier is a derivation of the two. In electrical systems and mechanical systems, power is a measure of work, which can take the form of physical work, as in moving a speaker cone, or thermal work (heat), which is actually more common in audio. In an electrical system where voltage, current, and resistance are present, power can be calculated as the product of voltage times current, and is measured in watts, which represents work done over time. (P = V x I — where "P" is power in watts, "V" is voltage in Volts, and "I" is current in Amps.) In terms of physical work, voltage would equal an amount of weight being lifted and current would be the speed at which it’s lifted. In the audio chain, we generally have a preamp followed by a power amp. The preamp boosts a low-level signal to line level, which is an increase in voltage (but not a significant increase in current). The power amp, which is the last stage in the chain, provides current via its power supply and boosts both it and the voltage from the preamp in order to provide enough power to drive a loudspeaker.
RCA: see phono plug
rpm: revolutions per minute
S-shaped tone arm: pulls toward the outside of a record and uses an anti-skate mechanism to counteract this pull. S-shaped tone arms position the stylus at the optimum angle for sound quality and the S shape dissipates external vibrations.
Send: An output on a mixer that sends that channel’s audio to wherever the send is routed. Sends included level controls and can be used for routing audio to external signal processors and usually include a return input as well so that the audio can be returned to the mixer.
Signal processor: generic term which loosely groups components such as compressors, limiters, equalizers, microphone preamps, noise gates, reverbs, chorus, delays, modulation, filters, and enhancers/exciters. All are used in audio to process sound in order to achieve a desirable effect.
Signal-to-noise ratio (SNR): the ratio of the desired signal’s volume to the unwanted noise, usually measured in dB. Manufacturers measure this ratio in many different ways, but basically the higher the number, the better and cleaner the signal.
Sound Pressure Level (SPL): the strength or intensity of acoustic sound waves, measured in dB. A typical SPL reading for a rock concert is 95dB.
Straight tone arm: exerts no inward or outward force relative to the platter. Straight tone arms minimize the risk of skipping at the cost of increased record wear and decreased sound quality because the angle of the needle doesn’t line up straight with the grooves.
Stylus (needle): the tip (and cantilever holding it) that picks up vibrations from the groove in a record so it can be translated into sound. These tips are usually made of industrial-grade diamonds to withstand the extreme pressure and heat generated as the tip goes around a record groove. Spherical (conical) styli feature a small sphere at the tip and are better for scratching, while egg-shaped elliptical styli are better for general-purpose use.
THD+N: acronym for Total Harmonic Distortion plus Noise. Smaller is better when it comes to this spec, which measures how transparently the mixer will reproduce music without distorting it.
Tone arm: the arm that holds the cartridge and points it in the right direction. The tone arm height is sometimes adjustable (most DJs leave it all the way up).
Tracking force: the downward force that allows the stylus to stay between the walls of a record groove. Adjustable via the counterweight.
XLR: a balanced, circular 3-pin connector typically used for microphone and line-level signals. Developed by the Cannon company, it is sometimes called a Cannon connector.
Part 6: Glossary