I don't know for certain but I love that album
At that time there had been a Maestro Exchoplex on the scene and one of the later square Binson machines too, but that doesn't mean they used them on that gig. A couple of years before that I saw John & Hank in cabaret and had a long chat with Hank and he showed me his gear back stage. He was using a Vox AC30 Bass and Watkins 'Shadow" echo box. . . . . . and still sounded amazing.