回答“Suddenly very thin sound.”It sounds like something has gone wrong with the cartridge. There's really no repairing the cartridge, so your best solution is to send the mic to Shure for repair/replacement. www.shure.com/service
回答“Broken ground on older SM-57”That is the ground wire. It's not needed, as Shure did away with that wire in newer versions of the SM57. However, I believe on the XLR end it was connected to pin 1 and on the cartridge end it was connected to the center post of the cartridge.