A portable computing device is disclosed. The BCM switching regulator detects whether it is operating in continuous conduction mode or discontinuous conduction mode, and adjusts the On-time, Off-time, or frequency of the power stage accordingly, so that the switching regulator operates in or near BCM. A device according to the invention is possible to implement in a small size and low weight due to reduced component count and thin access unit geometries. Each clamping device has a first arcuate recess and a second arcuate recess complimentarily corresponding to the first arcuate recess such that when the first and second arcuate recesses are combined to form a circular space, the pole of the cymbal assembly is clamped therebetween.