^ Pretty much this - Egnater offered a SL, SL2 and SL2x SL = superlead (plexi), SL2 = hotrodded superlead, SL2x = even more hotrodded, the GNR mod if you like :)
Youtube of a Egnater SL2x:
https://www.youtube.com/watch?v=sdc22Y7-d2k
Bruce also did a dual module of his EG preamp called an...