An external effect processor can be used (if you want to bypass the built in processor) with the PMP powered mixers (PMP1000, PMP3000, PMP4000, PMP5000 or PMP6000). Use the FX SEND connector to route to your effects device input. Then, plug your outputs from the effects device into a stereo channel. Make sure to keep the FX1 knob (and FX2 on the PMP6000) turned down to avoid a feedback loop.