Sine wave.The triangle-to-sine shaper uses the same JFet distortion circuit discussed in this LFO circuit. R19 is used to adjust the amplitude,and thus the shape of the sine wave. U2c buffers (and inverts) the signal,and again forms a 36 kHz low pass filter to reduce the glitch in the triangle. Kassutronics: VCO part 2: waveshaping Is this answer helpful?Thanks!Give more feedbackThanks!How can it be improved?How can the answer be improved?Tell us how Tim Stinchcombe - Tri to sine conversion Triangle wave to sine wave conversion. I find the idea of fashioning a sine wave from a triangle wave by passing it through some sort of nonlinear waveshaping device a fascinating one, especially since many of these devices, superficially at least, seem to bear no relation whatsoever to a sine function. 6-Diode 3-Segment Triangular-To-Sine Wave Shaper As the magnitude of the input voltage increases diode D6 (positive input voltage) and D5 (negative input voltage) are forward-biased. The current diverted to D5/D6 branch reduces the slope of the output voltage, this results to the second segment of the approximation to sine wave.