Connect an audio interface to you computer, via your USB port. ADAT recorders use 1/4" TRS cables to transfer sound, and most computers do not have 1/4" audio jacks by default. An audio interface solves this problem by functioning as an external sound card for musical equipment. You can purchase an interface at any music supply store.
Turn on the "Power" switch on your ADAT recorder (most models contain the "Power" switch on the back panel) and insert the tape containing the audio that you want to transfer to your computer.
Connect your ADAT recorder to your audio interface. Depending on your model, you may see anywhere between 8 and 24 "Output" jacks on the back of your recorder, each indicated by a number. Your jacks represent your tracks, or recording layers. Connect a TRS cable to each output corresponding to a recorded track, and connect the opposite end of each cable to a "Line In" jack on your interface. For instance, if your tape contains a voice recording on track 1 of your tape and a piano recording on track 2, connect cables to "Output 1" and "Output 2" on your ADAT recorder, and then connect to your "Line In" interface jacks.
Set up your audio interface as an input device in SONAR. Click the "Options" menu at the top of your screen and select "Audio" from the drop-down list. Click the "Drivers" tab and select the name of your audio interface on the list. If your interface does not appear among the driver list, take a moment to install the software that came with the interface. After clicking the driver, click the "General" tab at the top of your "Audio Options" window and select your audio interface on both the "Playback Timing Master" menu and the "Recording Timing Master" menu. Click "OK" to save your changes.
Create an audio track in Sonar by clicking the "Insert" menu at the top of your screen and selecting "Insert Audio Track" from the pop-up menu. Click the "Play" button on your ADAT recorder and then the "Record" button at the top of your SONAR window to transfer the recording from the ADAT recorder to SONAR. To record one track at a time and preserve your multitrack layering, select individual tracks on your ADAT recorder using the buttons labeled "1" through "8." Then create a new SONAR audio track for each corresponding ADAT track and transfer your recordings individually.