Alright, let me try to unbury this thread with an update. I recently got my own 380S, and have been trying a few PC's. The first thing I did was to call all the local Levinson dealers to see what they recommended with a right-angle plug. The all told me the same thing: "The power supply in the Levinson is so great, the stock cord is all you need". Well, not only did this sound a touch too convenient, considering the scarcity of appropriately-configured replacement cords, it sounded downright rehearsed, as if ML preps their dealers how to respond when hit with this obvious query.
So, with my BS detector telling me that none of the local guys had ever actually *tried* an aftermarket PC on their ML preamps, I began calling out of town dealers. Finally, the guy who owns Ambrosia in LA (clear across the country from me - was his name Larry?) gave me the straight scoop - yes, it can make a difference just like on anything else, even though it's true that the built-in AC prefiltering in the 380S is exceptional, so the differences may not be quite as big. Emboldened, I realized I didn't have to order a right-angle version of something without auditioning first - I simply jacked up the preamp on top of my VTL monos' removed tube cages, leaving the middle of the underside clear for the cord.
The short answer is that the cord can make a difference. Not the kind of difference I've heard with the preamp I'm replacing, and neither is the 380S anywhere near as positively affected by my feeding it balanced AC from my Power Wedge Ultra, sounding very nearly as good with the AC in regular mode, but small improvements were still to be had. I don't have any big-bux PC's around, but I tried the Synergistic Coupler, the Harm Tech AC 11, and the Shunyata Sidewinder, and all made subtle but worthwhile improvements. Right now, my plan is to go with the Sidewinder and send one back to be reterminated with the right-angle plug - this cord gave the best overall improvement, with quicker-sounding response, more extended top end, and tauter bass, with slightly less veiling and texture overall, more open and airy. Midrange 'richness' might be perceived by some as being greater with one of the other cables (or the stock cord), but none of them placed me quite as much in the presence of the performers as did the Sidewinder, although the other upgrade cords also lend a smoother sound vs. the OEM. The Sidewinder makes the whole presentation just a little more exciting and 'live'-sounding, as if a thin veil has been pushed aside.
As for the preamp, it's clearly the best I've yet owned, which ain't saying much taken out of context, but I plan to do some bypass testing to let me know where I stand in more absolute terms. I just need to get the cord squared away so I can integrate the thing in its proper place in the rack before being able to proceed with the necessary connections. But it's got a good rep, and I love the ergonomic flexibility and I/O capacity. Plus, I can finally connect my DAC in balanced mode, which is noticeably superior to single-ended (with the levels equalized), despite my having to revert for the moment to a since-superceded interconnect choice for its XLR's.
So to anyone with an ML pre out there who may be wondering whether they should bother with trying to find a right-angle cord, I say hoist up your preamp and try some of your straight ones out for yourself. The difference may not bowl anyone over (or maybe I just haven't tried good enough cords, but they've produced bigger results on other gear), but I think it's worth it if you're going to have this much invested in your preamp to begin with.
