Dynamic Audio Mixer
Posted on Jan 28, 2013 10606
The dynamic mixer combines two audio inputs by adding the primary signal, Input A, to a gain-controlled signal, Input B
. The unusual aspect of this circuit is that the average voltage level of Input A controls the gain of Input B. IC1 has the averaging function and many of the specialized gain blocks that the circuit requiresÂ· Rl sets the level of the primary input, Input A, to be passed to the output. R2 governs Input B"s level to the modulator, while R3 sets the level of the modulating signal. IC1 can be either an NE571N or an NE570N. The average ac signal at pin 2 controls the amount of signal that shows up at ICl"s output, pin 3. The primary signal gets to IC2, an NE5534N low-noise op amp, via CI and R7; the gain-modulated secondary signal arrives via pin 5 of IC1. IC2 sums the two signals. Potentiometers R4 and R6 make dc-offset and distortion adjustments, respectively. IC3, C7, R14, R15, Dl, and D2 form a filter for IC1.