I am trying to use the aux in on my Magellan 800 as a pseudo second channel to drive my keyboard bass. As I understand it, the Magellan has a built in fixed frequency HPF which I believe was added to the circuit to protect against speaker damage. An inquiry to Jeff Genzler revealed that the aux in bypasses both the HPF and the DI. I figure a suitable preamp pedal with a DI would do the trick, and would allow me to send separate signals to FOH while using the Magellan as a monitor. Are these types of filters commonly added to amps and/or preamp pedals? Are they designed for speaker protection or other purposes?