could a different power cord cure sibilance?

Thanks, I will try all of these suggestions. I use a Mint fof alignment, but loading and VTA are still mysteries to me.

Thanks for all the advice. I think Tvad is correct, the new pre revealed pre-existing flaws, particularly in certain recordings; no doubt Mechans is correct that in the end, a Steelhead or something equally adjustable will be required. I am using a low output Grado Reference into a 47K load. The Grado is supposedly insensitive to loading, which is why I didn't initially consider that a likely culprit. Nevertheless, as suggested above, I am trying different loads, starting with 800k. A pain, as resistors have to be soldered in (short term, a little less trouble than making some plugs) and, I assume, burned in for a while. 800k hasn't really solved the problem. I also realigned everything (with a Mint), messed with VTA, and switched power cords; all of that may have helped, a little, but not enough. Scouting various forums, some say the Grados are known for sibilance, but it wasn't clear if that is true of the higher-end ones (although, I was surprised when a distributor referred to the $1200 Grado as a "budget" cartridge. Try explaining that to non-audiophiles!) I will be asking for cartridge recommendations when finances permit.