use at least 2 oscillators (saws), on the first one set an lfo on the pitch to very fast speed and low amount to get a buzzy sound, then on the second shift the semitones down 12 so its playing on the same key but an octave lower. then depending on the plugin youre remaking it on try detuning the synth or use a slight unison detune and experiment with the mix levels of the second oscillator. should put you on the right track