Automatically Provide Gain to Low Level Signals and Attenuation to High Level Signals

    The high performance ST-GCA3 is an automatic gain control amplifier that provides a constant average audio output despite variations in input levels. It is used extensively in broadcast production and transmission, conferencing and sound reinforcement systems. The ST-GCA3 automatically provides gain to low level signals and attenuation to high levels. The adjustment rate is switch-selectable: SLOW for music or FAST for speech. With no audio on the input, AGC searching is limited to around 5 seconds. After a sustained period without audio, the outputs fade to a muted condition but instantly return to the proper level when audio is once again present. Accurate setup of the ST-GCA3 is simplified by the inclusion of two LED indicators which vary to show the amount of signal expansion or reduction. To produce equal available expansion and reduction, a normal audio level is applied to the input and the gain is adjusted for minimum response of both LEDs. The ST-GCA3 is often used in conjunction with the ST-CL2 Compressor / Limiter to provide a complete gain control package.   Application Diagrams Showing the ST-GCA3 in Use: AN-2050 User-Controlled Voice-Over Paging with 70 V Amplification of BGM and Paging