What I have is a power brick for drive power and a small, flat plastic USB adapter with sockets on three sides for the three different kinds of drives: SATA, 3.5" IDE, and 2.5" IDE. The fourth side has an on-off switch, USB cable, and a socket for the molex connector on the brick. Is this similar to what you have?
If I have a SATA drive connected, the power brick plugs into the USB adapter. If I am using a 3.5" IDE drive, the power brick does not plug into the USB adapter. It plugs into the drive.
Any IDE drive you plug into it should be set to "Master".