This paper provides a practical solution for precise and fast control of an elastic-joint robot arm using motor-side sensors only. We previously proposed a torsion-angular velocity feedback (TVFB) scheme for vibration-suppression control. The scheme utilizes an uncomplicated nonlinear observer based on a physically-parameterized dynamic model of the elastic-joint robot arm. The TVFB can be easily plugged into existing joint servos like PI velocity controllers. Using the elastic-joint robot arm, this paper experimentally demonstrates that the TVFB is equivalent to a nonlinear-model-based phase-lead compensator. Furthermore, several experiments are conducted to validate that the TVFB scheme has the capability to satisfy both vibration-suppression and fast-positioning control.