Yamaha EMX5014C Owner's Manual - Page 14

Mixer Basics Making the Most of Your Mixer A balanced cable has three conductors: 1) A ground conductor which carries no signal, just the "ground" or "0" reference against which the signal in the other conductors fluctuates. 2) A "hot" or "+" conductor which carries the normal-phase audio signal. 3) A "cold" or "-" conductor which carries the reverse-phase audio signal. Balanced Hot Cold Shield (Ground) Unbalanced Outer Insulation Signal Levels and the Decibel Let's take a look at one of the most commonly used units in audio: the decibel (dB). If the smallest sound that can be heard by the human ear is given an arbitrary value of 1, then the loudest sound that can be heard is approximately 1,000,000 (one million) times louder. That's too many digits to deal with for practical calculations, and so the more appropriate "decibel" (dB) unit was created for sound-related measurements. In this system the difference between the softest and loudest sounds that can be heard is 120 dB. This is a non-linear scale, and a difference of 3 dB actually results in a doubling or halving of the loudness. You might encounter a number of different varieties of the dB: dBu, dBV, dBM and others, but the dBu is the basic decibel unit. In the case of dBu, "0 dBu" is specified as a signal level of 0.775 volts. For example, if a microphone's output level is -40 dBu (0.00775 V), then to raise that level to 0 dBu (0.775 V) in the mixer's preamp stage requires that the signal be amplified by 100 times. A mixer may be required to handle signals at a wide range of levels, and it is necessary match input and output levels as closely as possible. In most cases the "nominal" level for a mixer's input and outputs is marked on the panel or listed in the owner's manual. + 20 dBu 0 dBu 0.775 V -20 dBu Most professional mixers, power amplifiers, and other types of equipment have inputs and outputs with a nominal level of +4 dBu. The inputs and outputs on home-use audio gear usually have a nominal level of -10 dBu. -40 dBu -60 dBu Microphone signal levels vary over a wide range depending on the type of microphone and the source. Average speech is about -30 dBu, but the twittering of a bird might be lower than -50 dBu while a solid bass drum beat might produce a level as high as 0 dBu. 14 EMX5014C Owner's Manual