This work presents a nonlinear model for Junction Field-Effect Transistors (JFET) that is suitable for audio emulations in real-time. The model is implemented by using Wave Digital Filters (WDF), which offer accurate and real-time capability on digital processors. As emulation examples, a common source amplification stage and an electric guitar preamplifier are implemented in real-time in a reconfigurable Field Programmable Gate Array. For verification purposes, the WDF simulations were compared with the ones obtained by SPICE circuit analysis software. It is demonstrated how the JFET model and the emulation examples accurately work in real-time, matching the harmonic content of the reference SPICE simulations.