I recently purchased a 2nd mic of this model. I was comparing the 2 of these mics and they sounded almost identical sonically and level wise...until I realized that my original fet had the 10db pad engaged! All settings were set the same including the 6db pad. The one that I had already is # 4619 and is labeled U47fet i P48. The one I just received seems older and is serial # G 1932, labeled U47fet i. I realize that the ciruitry may have evolved over the years of production, but does anyone have any idea of what might make the latter mic 10db quieter, but still sound the "same"? Are there schematics available for each of these? Any help would be greatly appreciated.