I would appreciate a bit of advice with regard to mounting non-isolated active devices on heatsinks.
While trying to get my feet wet with speaker amps, I bought a Gainclone kit (LM3886-based chipamp). The active devices included all require heatsink mounting, and all are non-isolated (LM3886T in particular instead of the isolated 3886TF). The kit does not include isolation pads, PEEK screws, shoulder washers, or any of the things we use here to attach high-voltage devices. I asked the vendor about this, and he said that I shouldn’t worry about it — he said that the tabs are grounded, and therefore do not need to be isolated from the chassis. I don’t understand this statement, and asked if “grounded” in this case means “the case is connected to safety earth on the inlet”, and if that implies that the amp cannot ever be connected to an outlet without a safety earth line (which I normally think of as necessary to protect against accidental shorts, but not as a hard requirement to prevent electrocution in everyday operation). He replied: “The power supply uses a UL Listed transformer, power entrance, fuse block, and power switch.”
This does not sit well with me, but before I push back on the vendor, I thought I’d ask here if I’m just ignorant. Is there something about UL Listed hardware that prevents a high-voltage device which is electrically common with the amplifier case from shocking the user? Is there a grounding scheme that negates this danger?