Op Amp clipping in Distortion Pedals

[antonis]

Cap inside NFB loop (the one in parallel with diode pair and Gain resistor/pot) acts almost equivalently to the one in parallel with shunting to GND diode pair..
(both are set between activated diode anode and virtual or actual GND..)

[FiveseveN]

If you want to avoid op amp clipping just use the inverting input:

[Steben]

Blues breaker is kind of atypical because it features a resistor in series with the shunt feedback diodes. This makes for a soft clipping tone.
classic circuits with "hard" feedback loop clipping are
- opamp big muff Pi.
- mxr dist II

Keep in mind though that opamp clipping especially when combined with "diode clipping first" usually does NOT sound less amp-like.
Tone shaping is far more important. The only really softer clipping classic amp I know are the non feedback cathode bias ones (Think VOX AC series, marshall 18W, ....).
The purple plexi pedal is actually only a chip clipping...
While the opamp big muff Pi is more a fuzz-tortion as the classic Pi is.

[Vivek]

Tone shaping is far more important.

I request you to share information/ graphs regarding Tone shaping in Distortion boxes and amps.

[Steben]

Tone shaping is far more important.

I request you to share information/ graphs regarding Tone shaping in Distortion boxes and amps.

A little experiment every enthusiast can perform is putting an EQ in front of a neutral drive pedal or channel.

less lows, much mids, medium high into drive => classic british rock.
medium lows, much mids, less high into drive => "woman tone".
much lows, medium mids, less highs into drive => emulated fuzz face (but without the slight layer of octave).

---- Regarding the fuzz face: even though the character of clipping is very assymetric, the tone sucking at full guitar volume (which is simply a low pass filter effect) which goes away with volume clean up (lows are cut more than highs with the roll of the knob) is such a distinct feature of a fuzz face, one cannot but conclude even there tone shaping is crucial in the "total effect of an effect". Put a 0.1 of 0.01 µF cap in front of a fuzz face and you have what you can call a high gain distortion pedal ----

much lows, low mids, much highs into drive => very very unpleasant tone

Of course, the rough labels "bass" "mids" and "treble" can be widened into 5, 7, 11 - band etc frequencies. A mid boost of 700Hz sounds different than one of 1000Hz. Is 2000Hz still mids or lower treble? .... etc every pedal has its own specific take on frequencies. Which again confirms tone shaping is crucial in the result.
A Boss metal zone is basically another back to back silicon diode clipper to ground but with a load of tone shaping possibilities in the post-eq. This makes it a very (at first) underrated versatile pedal.

[Vivek]

Blues breaker is kind of atypical because it features a resistor in series with the shunt feedback diodes. This makes for a soft clipping tone.

Soft clipping due to compliance resistor in series with clipping diodes