The Rotary machine on Mobius does not have a MIX control feature.
The Rotary machine produces the sound of a rotating speaker system with independent high frequency horn and low-frequency drum components. This effect is much more harmonically complex than, say, a chorus effect. Mixing in dry signal produces unwanted phase cancellations and alters the integrity of the rotary effect.
For a mellower rotary experience, turn the Depth control down to move the ‘microphones’ away from the cabinet. Or you can use a splitter box to run the dry signal to a separate amp, which is sonically different than summing the dry signal with the effected signal and running into one amp.