A valve assembly comprising: a one or more constant-flow, open centre valves; an open centre valve input port; a parallel power core operatively coupled to the one or more constant-flow, open centre valves; a power core input port separate from the open centre valve input port; a variable capacity pump fluidly connected to the parallel power core input port and the open centre valve input port; and a flow restrictor fluidly connected between the variable capacity pump and the one or more constant-flow, open centre valves, in which the parallel power core is not fluidly connected to an open centre core of the open centre valves downstream of the input ports, in which a smaller flow passes through the open centre valve input port than through the parallel power core, and in which at least one of the one or more constant-flow, open centre valves includes a valve spool having open centre notches and power core notches, the open center notches and the power core notches being configured to provide a signal flow through the open centre core which is less than a main flow through the parallel power core; the valve assembly further comprising: a signal port associated with the variable capacity pump, wherein an increase in hydraulic fluid pressure received by the signal port cause the variable displacement pump to pump hydraulic fluid at an increased pressure rate, and wherein a decrease in hydraulic fluid pressure received by the signal port causes the variable displacement pump to pump hydraulic fluid at a decreased pressure rate; a sense signal passage hydraulically connecting the open center core and the signal port, wherein the hydraulic connection between the sense signal passage and the open center core is located between the pump and the spool of the first one of the one or more constant-flow, open-center valves downstream of the pump in the open center core; wherein when activation of one or more of the spools of one or more of the constant-flow, open-center valves occurs in a manner causing one or more of the activated spools to be in either a first non-neutral position, or a second non-neutral position, increased hydraulic fluid pressure in the open center core is hydraulically communicated through the sense signal passage to the signal port. a one or more constant-flow, open centre valves; an open centre valve input port; a parallel power core operatively coupled to the one or more constant-flow, open centre valves; a power core input port separate from the open centre valve input port; a variable capacity pump fluidly connected to the parallel power core input port and the open centre valve input port; and a flow restrictor fluidly connected between the variable capacity pump and the one or more constant-flow, open centre valves, in which the parallel power core is not fluidly connected to an open centre core of the open centre valves downstream of the input ports, in which a smaller flow passes through the open centre valve input port than through the parallel power core, and in which at least one of the one or more constant-flow, open centre valves includes a valve spool having open centre notches and power core notches, the open center notches and the power core notches being configured to provide a signal flow through the open centre core which is less than a main flow through the parallel power core; the valve assembly further comprising: a signal port associated with the variable capacity pump, wherein an increase in hydraulic fluid pressure received by the signal port cause the variable displacement pump to pump hydraulic fluid at an increased pressure rate, and wherein a decrease in hydraulic fluid pressure received by the signal port causes the variable displacement pump to pump hydraulic fluid at a decreased pressure rate; a sense signal passage hydraulically connecting the open center core and the signal port, wherein the hydraulic connection between the sense signal passage and the open center core is located between the pump and the spool of the first one of the one or more constant-flow, open-center valves downstream of the pump in the open center core; wherein when activation of one or more of the spools of one or more of the constant-flow, open-center valves occurs in a manner causing one or more of the activated spools to be in either a first non-neutral position, or a second non-neutral position, increased hydraulic fluid pressure in the open center core is hydraulically communicated through the sense signal passage to the signal port. a signal port associated with the variable capacity pump, wherein an increase in hydraulic fluid pressure received by the signal port cause the variable displacement pump to pump hydraulic fluid at an increased pressure rate, and wherein a decrease in hydraulic fluid pressure received by the signal port causes the variable displacement pump to pump hydraulic fluid at a decreased pressure rate; a sense signal passage hydraulically connecting the open center core and the signal port, wherein the hydraulic connection between the sense signal passage and the open center core is located between the pump and the spool of the first one of the one or more constant-flow, open-center valves downstream of the pump in the open center core; wherein when activation of one or more of the spools of one or more of the constant-flow, open-center valves occurs in a manner causing one or more of the activated spools to be in either a first non-neutral position, or a second non-neutral position, increased hydraulic fluid pressure in the open center core is hydraulically communicated through the sense signal passage to the signal port.