It is very easy to measure the round-trip latency of your audio interface using a DAW and a digital cable.
Use these steps:
- Open your DAW and select your audio interface driver.
- Create a track with outputs set to the interface DO (i.e. outputs 9 & 10).
- Select a clip with a sharp attack, like a snare hit.
- Create another track with inputs set to the interface DI (i.e inputs 9 & 10).
- Arm recording on the second track.
- Connect the digital ports back-to-back using a suitable digital cable.
- Use your transport bar to play & record simultaneously. You will see the clip recorded on the second track, delayed by the round-trip latency.
- Most DAWs have a ‘delay’ value that can be set on the second track. Use this to offset the record time.
- Continue changing the delay time & re-recording the clip until the two clips line up perfectly.
Your delay value will be the precise round-trip latency.
You can verify the delay with a null test. Invert the recorded track & mix with the original; the samples will cancel out exactly.