What is the impedance of Duet (FireWire) headphone output? Chris March 02, 2021 22:45 Updated The headphone output has an impedance of 30 Ohms. Related articles Power Supply Information: Duet 2 ONE Headphone Output Impedance How does Duet 3 compare to other Apogee units? Ask Apogee: Explaining the Three Duets Does the Apple Thunderbolt to FireWire adapter work with Duet FireWire & Ensemble Firewire? Comments 0 comments Article is closed for comments.