The present invention enables, in assembling a rotary magnetic head drum assembly including a rotary magnetic head drum and a drum base, the automatic, electrical connection of the signal lines of the rotary magnetic head drum to external amplifiers. In the magnetic head drum assembly, lands (15) connected to the signal lines of a rotary magnetic head drum (1) are brought into contact respectively with the upper ends of the spring pins (20a) of a plurality of spring pin connectors (20) mounted on a connector base plate (18) attached to a drum base (11) supporting a stationary magnetic head drum (3), with the spring pins (20a) extending upward, and connected to external amplifiers, when the assembly of the rotary magnetic head drum (1) and the stationary magnetic head drum (3) is mounted on the drum base (11).