From Browne Amplification:

The Carbon X was born from a simple question posed by David Ryan Harris - "Can this be done?" The answer ("probably?") led to a journey of innovation and experimentation that resulted in the Carbon X. Imagine the fusion of two blue sides, the classic Carbon sound elevated to new heights. Inspired by DRH's request, we didn't stop at stacking two Carbons - we endeavored to make it even better. Stripping the right side of some of its sheen and headroom, we unleashed its grittier, raw essence and added a touch of sag, letting it unleash its barbaric yawp into the world of tonal richness.

But that's not all. To perfect the art of stacking and gaining it up, we introduced a high cut to the left side, taming the top end with surgical precision. The result is a pedal that not only embraces the bluesbreaker spirit but enhances it, giving you unparalleled control over your sound. We have sent several prototypes to DRH, editing and finalizing and the response is nothing short of love!