He said it was a line out jack, not a headphone jack. So, if it is indeed a true line out jack, that has been terminated to 1/8" socket, then there is not going to be a voltage issue. If it is actually a headphone jack, then that is not the same thing as a line out jack and there will be some voltage issues.
So, that's just something to double check on.
Otherwise, the info Jaxvon gave is correct. It should not matter and you can pick up adapters at Radio Shack that should be of decent quality. You could also pick up some raw materials at Parts Express . com and make your own adapter if you were up to the task.