Módulo multiplicador de onda

Doepfer A-137-2 Wave Multiplier II

Module A-137-2 is another version of a wave multiplier. In contrast to the A-137-1 Wavemultiplier I the A-137-2 generates four phase-shifted copies of a VCO signal applied to the audio input. 

The four shifted signals are added to the original signal to obtain a fat sound similar to five independent VCOs. 
The phase shifting is made by a simple circuit that works only for sloped signals like sawtooth, triangle or sine, but not for rectangles or pulses