Rocktron O.D.B. Blues - Manual (Page 4)

Introduction:
The O.D.B provides the best Blues tone and unparalleled dynamic
control you can get in one pedal. You get total control over the most
subtle nuances.
The O.D.B provides two Germanium clipping diodes that may be
independently assigned to provide soft knee clipping compression
applied to the to the positive cycle of the overdrive output, negative
cycle of the overdrive output or both! Thus providing the musician
total control of the overdrive characteristics providing even /odd
harmonic enhancement produced when Asymmetric clipping is
present.
SYMMETRICAL CLIPPING:
Assigning both + - diodes produces Symmetrical clipping (both
halves of the overdrive output waveform have equal volume).
ASYMMETRICAL CLIPPING:
Assigning only one of the diodes produces Asymmetrical clipping
(one half of the overdrive output waveform is larger than the other)
produces more harmonic overtones.
Germanium diodes are known for their magical soft clipping
properties.
The Drange Control determines how much Soft Knee Clipping is
applied.