The Symetrix 421m is a wide-range AGC-Leveler, a peak limiter, and a downward expander thatfeatures a microphone preamp, eliminating the need for a separate outboard microphone preamp insome applications. The 421m reduces the dynamic range of its input signal by the amount of itsratio setting. That is, if the ratio setting is 2:1, then 40 dB of input range turns into 20 dB at theoutput. A fast peak limiter puts an absolute ceiling on the output level so you know that peaks areheld to the level that you set. A downward expander reduces the gain when signal levels fall toolow to process, reducing the noise buildup at low signal levels. Speech filters allow a reduction ofreduction the bandpass of the 421m to minimize feedback or amplifier power waste caused byspurious out-of-band signals.
AGC-Levelers can be used anywhere that you might need to reduce the dynamic range of an audiosignal over a wide range of signal levels. Possible applications include: tape duplication (especiallycassette), driving telephone lines, driving broadcast or STL transmitters, podium or lectern micro-phones, paging systems, unattended sound systems, and music recording.