The EPL included in the EC preamp provides the flexibility to enable you to insert just about any outboard analogue signal processor into the signal chain, or even make a push-button channel swap. It can alternatively be used to route the signal to a HT decoder and return the L & R signals to the preamp, with the rest of the signals going to center, sub, rears, and etc. actuated by push-button, and a simple straight through for stereo-only operation.
I hope this give you an idea of the flexibility of the EPL. This is similar to the concept of switching the tone controls in and out of the circuit.
I use mine for an outboard noise filter, used only when I feel the need to address some analogue signal noisiness.
