Hi! I want to try a preamp pedal on a combo I have, but my combo doen't have a preamp input and I don't want to go through the combo's preamp. My combo has a Aux in input, with the volume controlled by the Master knob. Can I use it in for that matter? Is it safe? If so, which output from the pedal should I use, jack output, line out or headphone out? Thank you!