just picked up a 70/71 Ampeg b15N and wanted to get some info from more experienced users of this period of the amp. I played one about 7 years ago in this dusty "rehearsal" studio in New York and have wanted one ever since - have messed around in stores on some others in the meantime but money's never been right until now. All I know is that the ones I have been playing were blue face (from what I know that puts it at 68-73?) so thats what i got. First impressions are great so far but have questions... mine came with a JBL D140 in it but also shipped with the original square-magnet. anyone have thoughts on what they like for what? speaker rattle and slight distortion at about 10:30 on the volume -- is that normal? maybe a function of the changed speaker? tubes? your recording "settings" -- eq, mic, mic placement. etc. thanks.