OK, I just finished listening to Led Zeppelins" Heartbreaker". I believe this to be off the 2nd album? Its been probably 25 years since I heard it last, Have that one on vinyl stashed away in the basement. Anyhow.... does any one know what JPJ used as far as bass and amps (effects) to achive that nasty growl? What a wonderful sound he had there. Almost like a really boomy bottom with a growl like I have not heard before up top. Does any one know what I mean? Now I remember why I loved that album so much! Not to mention the bass in the" Lemon" song!!!