I understand the equations to compute Ids (current drain to source) for a large signal mosfet amp in saturation but I'm not sure how to find the K (constant) : Ids= ((K/2)(Vgs-Vt)) . I've looked at several data sheets for the mosfet I'm using, (IRF530) but no luck. Any help out there?

 

This thread should be of interest: https://www.diyaudio.com/forums/solid-state/180320-parameter-mosfet.html