Hey guys. Sorry to beat the dead horse... Assume a modern build, with a three prong AC cord, and the green (3rd) wire firmly bolted to the chassis. The chassis is now at the same potential as the human reaching over to touch it. Zero volts. Grounded. Best practice multi-star grounding is observed, ala Merlin (or a bus, or a hybrid approach). Fiber shoulder washers isolate the chassis from the jacks. Common return paths (aka 'grounds') are considered based on the currents they serve, and differing current levels are kept apart. I'm good with all of this, until the last bit: connect the main star point (or end of bus) to one location (and one location only) on the chassis. Either near the power supply, or near the input jack. I get the rationale for one-and-one-only... but why do it at all? Oh wait, the chassis won't be able to function as a RF shield. OK, so we use a death cap at the input jack, which shunts off any high freq AC to the chassis before it gets into the preamp. Can we stop there? Beyond this, is there any functional reason to connect the chassis to our carefully planned return path layout? I can't think of one, so I'm guessing it's about safety. What are the failure scenarios in which this connection to the chassis will help? In other words, are the fuse and the AC safety ground wire enough? I've read a lot of sources, and a lot of details, but this one point tends to be more of a given, and thus not well explained. Some imply it's all about the shielding, which the cap corrects. I suspect it's something of a belt-and-suspenders thing, which I'm all FOR. Just trying to understand the details. [ EDIT: the one reason I read about which seemed to make it necessary is to keep the chassis' of multiple devices, which are connected together, at the same ground potential. Not sure I understand why this matters, but yeah, if the chassis of the amp and the external preamp, or the outboard reverb unit, etc, are each entirely floating, it doesn't really matter if they're precisely at zero volts, but it might matter that they be the same. And they probably wouldn't be. ] Thanks.