Recording vocals over guitar track

Im using Sonar 4 and I open a new project, I record a guitar track under audio 1 w asio stereo output. Then I go to audio track 2 and choose the same output and record the vocals while listening to track 1 track2 picks up the guitar coming out of the monitors and when i play back both tracks track 1 sounds like its in a box . how do i hear what i played on track 1 and record my vocals without re recording my guitar on track 2 there has to be a trick to this that im missing somewhere