iLounge and MacRumors forums member logicalnoise have noted that iPod Classic Firmware 1.1.1, which is now available via iTunes, has corrected a hissing problem that had been plaguing users when their classics were placed into standby mode.
Before the update when I went into standby my speakers would pop and I'd hear some soft static then when I switched on the button lock my speakers would pop again. After updating this morning going to standby is a silent operation again.