CM6533-N Datasheet, PDF (23/60 Pages) C-Media Electronics – USB 2.0 Full-Speed compliant

CM6533,CM6533N,CM6533X1,CM6533DH
USB Audio Chip
6.2 Recording Equalizer
CM6533/CM6533N/CM6533X1/CM6533DH also provide five (5)-band equalizer for the input. It can be used to
compensate the frequency response of microphone unit. Clients could fully customize all EQ coefficients (center
frequency, gain values, and bandwidth) through embedded FLASH.
6.3 Recording AGC
Automatic Gain Control (AGC) is an automatically controlled method to adjust with respect to the intensity of
signal; AGC closes the return circuit which is by the negative response system too.
AGC is by way of compressing volume, will increase Gain first when AGC is started to set up the upper and lower
limits of the signal. Then, it will compress the dynamic range of sound. It usually uses the occasion of AGC, should
there be recording and producing and speaking sound, or volume is being changed under little environment. If the
lasting low voice of volume, AGC will enlarge volume then volume is sustained loudly while AGC will reduce volume.
Features
Programmable AGC Parameters
Selectable Gain from –12 dB to 45 dB in 1-dB Steps
Selectable Attack, Release and Hold Times
AGC Enable/Disable Function
Limiter Enable/Disable Function
Pre-Detect Limiter Level Function
Two-Channel AGC Independent
Under input source types, to set AGC gain max/min limit
Dig mic
+20 ~ -16DB
Analog mic
+30 ~ 0DB
0xf9= 0x24 (max)+fix gain(9db) =0x2d
0xfA= 0x00(min)
0xf9=0x0F+fix gain(9db) inv -> 0x39(max)
0xfA=0x2D
inv -> 0x12(min)
AGC variable description
Fixed Gain: The normal gain of the device when the AGC is inactive
Limiter Level: The value that sets the maximum allowed output amplitude
Attack Time: The minimum time between two gain decrements
Release Time: The minimum time between two gain increments
Hold Time: The time it takes for the very first gain increment after the input signal amplitude decreases
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