Jim Kelley wrote about his 3rd generation of amps:
"The preamp must have worked well enough because I decided to incorporate the idea into a new version of FACS amp I called the Line Amp. For this amp I devised a new tone control that became saddled with the inglorious misnomer 'Pre-EQ'. In production it in fact became a passive, infinitely variable, post distortion, LC mid-boost and cut EQ control. As far as I know, it was the first of it's kind."
Allan Holdsworth played one on his record "Metal Fatigue".