Funny thing about Jerry is that he had what to most of us would be clean headroom, but he turned up SO LOUD that he ran out of headroom. That's where Jerry's magic tone comes alive, when that headroom gets eaten up, when the speakers begin to saturate a little, when the Mac begins to clip a little. All that happened for Jerry at such extremely loud levels, it's virtually impossible for any of us mortals to re-create it just like the original. Even for Mattson in DSO with all the right gear, he simply can't run it like Jerry did. It would not only be too unpleasantly loud for himself, but the band and the soundman and the crowd couldn't tolerate it. I've been with him on stage exploring the various ways to connect the cabinet to the different impedance taps on the Mc2300 and it reinforces just how loud Jerry was.
I'm not pushing the Earth Drive here, but I think that all of us seeking to re-create a great Jerry tone need to explore ways to either scale it all down in size and power and also find ways to get (emulate) that maxed out smoothing, clipping, ice-pick removal and in a way that suits our stage settings, at a comfortable and correct loudness. Simply turning down a full-blown Jerry rig may make things quieter, but the tone becomes tragically sterile and lifeless and the pick attacks are brutally jabby, ice-picky. We NEED some form of clipping to smooth off the attacks and get some harmonic "juice" in there like Jerry had.
Jerry's tone was virtually all treble, but he controlled that voice with his hands and pick and he smoothed it out with clipping. I prefer to find a way to use a smaller Mac and fewer JBL's to achieve something very close. But for those with 2 or more JBL's and lots of Mac power, the Earth Drive is one way to achieve a symmetrical type clipping and smoothing. It's just one way of many. Personally, knowing that so much of Jerry's magic tone came from a JBL being pushed past its limits and compressing, clipping, saturating, that suggests to me that for many of us at reasonable stage volumes, we should probably be honing in on using just one JBL, and likely a K120 not an E120, and trying to use some Mac power in the 75 to 120 watt range. To me, that setup will let us get a bit of JBL distortion, a bit of Mac distortion, and all at an acceptable stage loudness, still loud, but doable.
I still hear far too many examples of guys going for a Jerry tone and it's just too brutally clean, way overpowered, and the JBL's aren't even close to being driven hard enough to do their musical magic, that squirty, juicy, sparkly, kind-of-dirty thing they do when stressed. Once the rig is dialed in, the rest is up to the player's hands, to play mostly in a high-headroom, clean zone but where the pick attacks and hard strums get clipped, riding that range where the clipping threshold is right there controlled by the hands and also with the guitar volume knob set in a place where you can easily push things up closer to the clipping threshold or turn down to where virtually all the clean headroom is intact. I really think that's the zone where Jerry operated. Just remember, Jerry blew speakers quite often. That tells us a lot actually.
... and it's just like any other day that's ever been...