The R-122 is basically a phantom powered version of the R-121, coupled with a larger transformer and active electronics. This gives the R-122 13 db more level without any increase in noise (all of the extra level comes from the larger transformer; hence that wonderful thing called "free gain"). The extra level is useful when recording low level sound sources like acoustic instruments, vocals, soft percussion and spoken word. Both mics utilize a 2.5 micron aluminum ribbon and are capable of handling a maximum SPL of 135db (at 20 Hz!). The R-122 is also more forgiving with regard to preamplifier input impedance and long cable runs. The R-121 is generally favored for loud sound sources, such as loud guitar amplifiers, toms and kick drum.