A hydraulic system for a multi-process machine, the multi-process machine including a base machine, a boom assembly comprising at least one boom, and a felling head for felling and further processing trees, the felling head being arranged to be suspended on said boom via a joint, said felling head including: • a rotator for rotating the felling head, • a suspension device, its actuator unit and a frame for the felling head, including log feeding device complete with hydraulic motors, and wherein the hydraulic system comprises: • a hydraulic pump on the base machine, • a dedicated valve assembly for supplying medium from the hydraulic pump to the felling head, • a hydraulic pressure line and a return line led from the dedicated valve assembly of the base machine to the felling head, comprising separate valve channels on the pressure side and the tank side, • at least one said hydraulic motor for operating the feed device, • at least one pressure accumulator placed in the system for increasing the instantaneous output with said motor, characterised in that • a dedicated supply valve, a supply line (A/B) and a return line (B/A) are in the felling head, the dedicated supply valve connected to said hydraulic pressure line and the return line and actuating the supply line (A/B) for feeding medium to said hydraulic motor and the return line (B/A) for returning medium from the hydraulic motor • said pressure accumulators are at least two (211 - 214), each arranged with a different pre-charge pressure, • the hydraulic system includes a logic control for implementing pulse-operated use of the pressure accumalators mainly for sawing and log feeding including their auxiliary steps, and where the pressure accumulators are used only for improving log feeding, and the hydraulic system providing a direct feeding line from the accumulators to the said hydraulic motor, whereby the system further includes • a first auxiliary supply line from the pump to the pressure accumulators, a first end connected between the pump and the dedicated valve assembly, and being a straight line comprising only a first control valve, and • a second auxiliary supply line as said direct feeding line led directly from the pressure accumulators to the forward side of the hydraulic motor and having a second control valve for supplying the pressure of the accumulator directly to the motor. • a rotator for rotating the felling head, • a suspension device, its actuator unit and a frame for the felling head, including log feeding device complete with hydraulic motors, and • a hydraulic pump on the base machine, • a dedicated valve assembly for supplying medium from the hydraulic pump to the felling head, • a hydraulic pressure line and a return line led from the dedicated valve assembly of the base machine to the felling head, comprising separate valve channels on the pressure side and the tank side, • at least one said hydraulic motor for operating the feed device, • at least one pressure accumulator placed in the system for increasing the instantaneous output with said motor, characterised in that • a dedicated supply valve, a supply line (A/B) and a return line (B/A) are in the felling head, the dedicated supply valve connected to said hydraulic pressure line and the return line and actuating the supply line (A/B) for feeding medium to said hydraulic motor and the return line (B/A) for returning medium from the hydraulic motor • said pressure accumulators are at least two (211 - 214), each arranged with a different pre-charge pressure, • the hydraulic system includes a logic control for implementing pulse-operated use of the pressure accumalators mainly for sawing and log feeding including their auxiliary steps, and where the pressure accumulators are used only for improving log feeding, and the hydraulic system providing a direct feeding line from the accumulators to the said hydraulic motor, whereby the system further includes • a first auxiliary supply line from the pump to the pressure accumulators, a first end connected between the pump and the dedicated valve assembly, and being a straight line comprising only a first control valve, and • a second auxiliary supply line as said direct feeding line led directly from the pressure accumulators to the forward side of the hydraulic motor and having a second control valve for supplying the pressure of the accumulator directly to the motor.