Wideband digital distributed communications systems (DCSs) employing reconfigurable digital signal processing circuit for scaling supported communications services are disclosed. The DCS includes a head-end unit that includes front end downlink signal processing circuit to receive and distribute downlink communications signals for communications services (i.e., communications bands) to remote units. The remote units also include front end uplink signal processing circuits to receive uplink communications signals to be distributed to the head-end unit. The front end signal processing circuits are either equipped with broadband filters, or such filters are eliminated, to allow the DCS to be scaled to pass added communications bands. The front end processing circuits include analog-to-digital conversion (ADC) circuits for converting received analog communications signals into digital communications signals so that the digital communications signals can be processed by digital signal processing circuit that can flexibly be configured and reconfigured to support the added communications bands.