Yes, in balanced headphone output mode only the tip (+) and ring (-) connections are used on the TRS jacks. In most cases, there wouldn’t be anything to connect the shield to on the headphone side of things anyway.
- Pin 2 is + (hot)
- Pin 3 is - (cold)
- Pin 1 is the shield
Depending on what you’re connecting it to, you may need to only connect pin 1 on the source (DAC) side of things. Pin 1 should go to chassis ground, but some gear connects it to signal-ground instead - which can result in ground loops/hum.
Best way to go is to start with Pin 1 connected to the shield on both ends, and if you get hum or noise then just cut the connection to pin 1 on the amp-end XLR connection.