yes, you can use computer DDS tapes in DAT recorders. Most DAT manufacturers recommend not using a tape over 2 hours. in computer world, that's a 60m (meter) tape. many people, though, also use 90m tapes for 3 hours of runtime. There has been a long debate about whether or not the 90m tapes will wear out your DAT deck quicker than if you just used 60m tapes.
