With the increasing prevalence of the Bose Aviation X headset as an alternative to the David Clark H10-76, we find it important to note that the STEREO version supplied from the Bose factory is configured for MONO.

So what's the magic?

The Aviation X has an electronics module inline with the headset lead that includes a battery pack, the noise canceling circuitry, and volume controls. Inside the battery compartment, very inconspicuously hidden under the installed batteries is a small bank of dip switches. One of these switches is labeled "mono/stereo". The factory presets these to mono.

The solution is to flip the dip switch. Now you have stereo headset.