I was analyzing my Marantz service manual and it's smpss power supply. There is an input choke filter immediately after the AC input. There are two small ferrite beads on the PCB layout. Also the output of the SMPS which goes to the main board has a ferrite beads clamped on the DC power cable. But the audio power cable does not have the ferrite beads clamped. There should be some wisdom in this implementation. As Prem says, probably the ferrite robs the juice out of music. Now don't tell me this is for cost cutting às they cost hardly 50/- bucks.