Hard Clipping Diodes in Greer Southland - Do Nothing Diodes?

[playpunk]

Hey guys. It's been a minute since I've built a pedal, mostly because I convinced myself that the two (excellent!) optical compressors I built weren't working right. I was just imagining distortion, though, I guess, as they're working now.

Anyway. I want to build a 2 in 1 Greer light speed and southland, but want to differentiate the sides a bit more. The southland is essentially a light speed with some small changes, including bat41 diodes as hard clipping diodes, along with the same asymmetrical 1n941's in the feedback loop like the light speed.

Do those bat41's do anything? Is there enough voltage to even hit the hard clipping diodes after the feedback loop diodes?

[mauman]

Boy, nearly identical is right!  Here are the two schematics (PedalPCB versions) for comparison.  Mach 1 = Lightspeed, Southern Belle = Southland.  I agree that you might want to differentiate the two sides a bit more, unless you're going for the King of Tone sound with two nearly identical sides.

The only differences are the Gain pot value (500k vs 1M), addition of the two BAT41 hard clip diodes, 2nd op amp feedback resistor (4.7k vs 22k) and the volume pot value (100k vs 250k).  Southern Belle would have a little more gain than Lightspeed in the first op amp (higher value pot) then the added clipping from those BAT 41's, then additional gain in the 2nd op amp.  Volume pot difference is just a matter of where you'd set the knob to get the same level.

What the BAT41 diodes do is limit the input level to the 2nd op amp, their Vf is about like a Ge diode, 0.37 V at 1 mA in each direction (0.74V peak to peak.)  There will be plenty of voltage for these diodes to clip as you turn up the Gain pot, but it's a little odd to do symmetrical clipping after the first op amp generates an asymmetrical waveform (3 diodes in one direction, two in the other.)  The BAT41s will tend to make the waveform of the Belle more symmetrical, the more you turn up the Gain pot.