The SA-XR25 and 45 use 3) TI TAS5182X1 chips in the audio section to supply the switching mosfets. The SA-XR50 and 70 only uses 2 of the TI TAS5182 chips. For the front channels there are quite a few small chips and surface mounted components in place of a single TAS5182. The switching mosfets are the same in all channels as are the output filters.
