Yellow Shark Nature control - what does it do?

[rowland1]

Hi, I just completed my Yellow Shark build. The kids are asleep, so I can't really crank it yet. But at low volumes it sounds great so far. I was a little surprised by the Nature control. I assumed it was a tone control, but noticed it impacts the overdrive quality more than tone. Since it has LEDs for clipping, I turned off the lights and watched the LEDs as I strummed and fiddled with the knob. There is more light emitted as you turn the knob counter-clockwise.

Anyway, I looked at the schematic (which is almost greek to me) but I can see that the Nature pot is in a loop with the LEDs. So does the Nature control blend in LED clipping? Can someone explain what's going on with the Nature control? It seems like a cool and novel idea. Is it?

Thanks for any help you can give me in understanding this!! - Rowland

[madbean]

The Nature pot partially controls the total gain allowed by the op-amp, where the waveform is clipped and also which frequency range is boosted at Q1...all at the same time. It is pretty clever. When the pot is fully counter-clockwise, C3 and C4 are parallel to ground which results in a very broadly clipped waveform. This also means that there is a high resistance to ground (50k) in parallel with R11 and in series with C5.

When it's all the way clockwise, the resistance between C5 and ground goes to zero, which means that Q1 is boosting more midrange. It also means that there is a high resistance between C4 and ground. The result of this is that the overall gain of the feedback in the op-amp stage is decreased. That's why your LEDs are lighting up more when the knob is all the way to the left: that's where you have the highest gain possible in the FB loop.

[rowland1]

Thank you Brian!!
I really appreciate the excellent explanation and response to my questions. You made it undestandable and taught me a few things. Thanks again!!