Described herein is a rotary head cylinder assembly including a fixed lower cylinder for guiding travel of a magnetic tape, an upper cylinder rotatably mounted on the lower cylinder and provided with a number of magnetic heads, and a circuit board fixedly mounted on the upper cylinder and supporting thereon amplifiers in positions in close proximity to the respective magnetic heads. The circuit board is provided with notched portions at the outer periphery to permit direct access to screws for adjusting the height of the magnetic heads as well as to holes for adjusting the position of the magnetic heads from above the top side of the cylinder, while preventing interference by undesirable signals.