Positive feedback after shunt clipping diodes

[Vivek]

Please help me understand positive feedback after clipping diodes,

Versus negative feedback after shunt clipping diodes

[iainpunk]

the top one isn't positive feedback, there is a buffer in front of the ''in'' connection. remember superposition, buffers have a near 0 ohm output impedance, thus the path back is not letting signal through.
this path is unidirectional, its feed forward!

the sweet honey OD uses the feedback to sharpen the knee of the diode clipping and the LED's make sure that the op amp doesn't clip to the rails.

cheers, Iain

[teemuk]

Yes, rather than positive feedback in top example I see two signal paths and subsequently a variable degree of mixing between dry signal and signal with more harmonic content introduced by clipping. Depending on magnitude of blending the output signal will have none to very little additional harmonics (clen, undistorted signal) or a lot of additional harmonic content (plenty of distortion). In the mid-range of dial there is intermediste amount of distortion introduced.