I've been designing and tuning the peak detector of the 2-source 5.1 channel summing box I'm going to build. The detection envelope can be seen in green, the horizontal lines indicate the threshold voltages for 0, -6, -12 and -18 dB, and the square pulses are the LED on-off control signals for those thresholds. The waves are curved at the top because I'm inducing hysteresis into the comparators to prevent from from switching with the ripples on the detection envelope.