Cartridge holder with a cartridge height position locking mechanism accommodating tape cartridges of differing tape widths

A magnetic recording/playback apparatus comprising:

• a cartridge holder into which one of a first cartridge and a second cartridge having a greater dimension than the first cartridge is selectively inserted, the cartridge holder including a cartridge supporting member that includes a horizontal plate portion, a first side plate portion, and a second side plate portion, which portions support a bottom face, a first side face, and a second side face, respectively, of an inserted cartridge. corresponding to one of the first cartridge and the second cartridge;
• a cartridge upper face holding member configured to hold down an upper face of the inserted cartridge which cartridge upper face holding member is normally positioned at a first height position for holding down an upper face of the first cartridge;
• a cartridge upper face holding member supporting mechanism configured to support the cartridge upper face holding member and move the cartridge upper face holding member in a direction for changing a height position of the cartridge upper face holding member with respect to the cartridge supporting member;
• and a lock mechanism configured to lock the cartridge upper face holding member in the first height position;
• wherein the cartridge supporting member and the cartridge upper face holding member define a cartridge accommodating space for accommodating the inserted cartridge;
• the lock mechanism is configured to remain locked when the first cartridge is inserted, and be unlocked when the second cartridge is inserted;
• and
• when the second cartridge is inserted, the cartridge upper face holding member is moved to a second height position that is higher than the first height position, and a size of the cartridge accommodating space is changed to correspond to a size of the second cartridge.