Sirus Live M416, Manual

Page: 30 / 45

30 / 45
10.4.3. Signal Generator/Pink Noise
Press to select either pink noise (up position) or a 1 kHz sine wave tone as the test source. Start with
the trim control turned fully down. The generator ON switch is recessed to prevent accidental
operation. Press this with a pen or pointed object. The green indicator lights to warn the generator is
enabled.
The generator signal is routed to any source selected on the switch bank above the TALK switch. Use
the signal to test the loudspeaker system and the lineup connected equipment. Pink noise is useful for
quickly testing the full range frequency operation and phasing/polarity of loudspeakers. The 1 kHz
tone is better suited to lining up equipment with the steady reading on the meters.
Warning: We recommend you turn off the signal generator once you have finished using it to
test and line up your system. This will prevent accidental operating during the show.
11. Applications and operating tips
The following is a collection of brief descriptions, application notes, hints and tips to help operator
understand some of the technical terms referred to, and to get the most out of the uniquely capable
mixing console live sound mixing console. They are written as a concise reference to spark your
imagination to creatively and effectively deal with the many challenges now faced in modern day
mixing.
11.1. Gain structure
The term used to describe the gain (level) matching of the signal through the audio system chain.
Each item in the equipment chain has its own optimum (‘nominal’) operating level determined by its
electrical circuits. If you overload it with a signal that is too high then its output tries to produce more
voltage than its power rails can provide resulting in harsh sounding distortion as the audio signal is
‘clipped’. If you work with a signal that is too low then you are likely to hear residual hiss of the circuits
as the ‘noise floor’ is amplified along with the signal. The optimum operating level is the point at which
the signal high enough above the ‘noise floor’ is amplified along with the signal. The optimum
operating level is the point at which the signal is high enough above the noise floor so that the hiss is
not to heard (good ‘signal-to-noise’ ration, the SNR), yet provides enough space (‘headroom’) before
clipping to allow for the louder, dynamic musical movements without distortion. ‘Dynamic range’
specifies the maximum range between noise floor and clipping. It is the sum of SNR and headroom.
The larger the figure the better…less noise, more headroom, more forgiving to wide ranging signals.
A microphone produces a very tiny signal, for example -50dBu (a few mill volts). This should be
amplified by the channel preamp to the optimum operating level of the console circuits, around
0dBU/077V, well clear of the noise floor (typically less than -90dBu), and with good headroom