Hi, Asparaguy
You need a Step/Dir to 10 + - Volt Board, Hears a tester you can make.
Zero the volts before hooking it up to your servos + - leads, It will let you test them, Disconnect batteries when not being used.
Your "Step/Dir to 10 + - Volt Board" will need an Encoder input, From your servo amp or a separate Encoder.
Hope this Helps, Chip