I know this thread is a bit old, but there is some incorrect information going around that the ES-50 is not able to slave a tape machine to a DAW without issues (specifically the runaway slave problem that sweetbeats mentioned). I have successfully slaved my TASCAM 48 to Pro Tools using the ES-50 and it works perfectly. If I change the cursor position on the time line in PT, the 48 chases and locks to that position. I'm not sure exactly what went wrong with sweetbeats attempt to slave his 58 to Cubase. Could be the cables were not wired correctly, or the ES-50 or the 58 were malfunctioning. But this can be done! Anyone who attempts this - DO NOT GIVE UP HOPE. One piece of advice I'd like to share is something I found on a handwritten note tucked inside the documentation binder I got with my ES unit: "roll machines in play mode before using setup". This seemed to make all the difference for me. Hit Play on the DAW and Play on the tape machine before you press the ES setup button. The ES will report problems (blinking setup light) but it will complete and it will work.