Synth Schematics --::-- Envelope Follower Envelope Follower. Unlike the usual envelope detectors using a diode and a lowpass this circuit is combined from a peak hold that is sampled and held after the zero crossing. The CMOS switches discharge the peak hold cap after it has been sampled. The Technology of Auto-Wahs / Envelope-Controlled Filters First, the output signal of the envelope follower has to be of sufficient amplitude (current OR voltage) and appropriate polarity to drive the control element. Not much problem there. In most cases, this simply means providing appropriate gain within the envelope follower itself, or feeding it with an already boosted (or attenuated) signal.