Hopefully, you’ve looked at the section on line and mic level signals, if not: go and read it first.
So, you’ve plugged in your signal. But the desk is a series of electronics which can’t cope with a very strong or very weak signal and so we need to give it an electrical level which is ‘just right’. To do this, we alter the gain of the desk which increases or reduces the signal to that required by the desk.
Range (RNG)
The range button (sometimes named line) tells the desk that you are sending it a line level signal instead of a mic level. By depressing this button, the desk knows that a large signal is being used and so knows to be less sensitive.
Setting the correct gain
Send a signal into the desk (play the CD, guitar, start singing etc)
Press the PFL (pre-fade listen) button – this is sometimes marked SOLO depending on the desk
Look at the LEDs (or dial) on the desk which indicate the signal strength
Alter the gain control until the orange LEDs begin to flash occasionally
Release the PFL button
Repeat for all the other channels on the desk
The correct level
A quiet singer using an insensitive microphone will generally produce a very small signal and therefore the desk needs to pre-amplify it a lot: the gain will be high.
A very loud drum miced with a sensitive microphone will produce a very high signal and therefore the desk needs to pre-amplify it little: the gain will be low.
Phantom Power (+48)
Usually close to the gain controls is a button labelled +48V. This is nothing to do with the gain but instead, feeds 48 volts along the mic cable; some equipment such as condenser microphones require such a power source. Sending phantom power to a microphone not requiring it won’t theoretically damage it but a dodgy connection or incorrect cabling could result in a destroyed piece of equipment. If you don’t need it, don’t use it!
Phase reverse
This control reverses the phase of the sound, meaning that sound peaks are troughs and vica versa. A very important property of such a sound is that when an sound is combined with the same sound with a phase reverse, the two cancel each other out.
The phase reverse button is best used on one channel of a pair of microphones: micing snare drums using teo mics or employing 2 mics on a chorus.
Backstage
Technical Services,
University of Bath Students' Union, Claverton Down,
BATH, BA2 7AY Generously supported by the University of Bath Alumni Fund.
