Liquid ejection apparatus and head unit

A liquid ejection apparatus comprising:

• an ejection head configured to eject liquid;
• a liquid reservoir storing liquid ejected by the ejection head;
• and
• a pressure control mechanism configured to control a pressure of liquid supplied from the liquid reservoir and supply the ejection head with liquid at the controlled pressure through a liquid flow path section, the pressure control mechanism comprising a pressure chamber in liquid communication with the ejection head through the liquid flow path section, a liquid passage chamber configured to receive liquid supplied from the liquid reservoir, a valve element configured to open and close between the pressure chamber and the liquid passage chamber, a lever member connected to the valve element at a load and connectable to a pressure receiving member for a pressure of the pressure chamber at an effort, the lever member being provided rotatably about a fulcrum, and a biasing unit configured to bias the valve element in a closing direction at the load of the lever member, the pressure control mechanism being configured to control a pressure of the pressure chamber,
• wherein the pressure control mechanism is configured such that a lever ratio, which is a ratio of a distance between the effort and fulcrum of the lever member to a distance between the load and fulcrum of the lever member, is greater than 1 and less than 5.