Question

I can hear playback by connecting my headphones to the "main out" channel, but not when the headphones are connected to headphone channel one or two.  

I am using Logic Pro X version 10.2.0 on a Mac OS X El Capitan 10.11.1.

I am using the Studio 192 192kHz/24 bit, 26x32 USB 3.0

The answer is probably simple, but there is not much information on this.

Answer 1

This is covered in the manual under the section about the front panel and "Headphones":

https://pae-web.presonusmusic.com/downloads/products/pdf/Studio192_OwnersManual_EN_01252016.pdf

 

I've attached a link to a screenshot of the specific section:

http://answers.presonus.com/?qa=blob&qa_blobid=18348949914960201227

Comments

Here's a direct quote from the manual:
"Each headphone output is provided with its own unique output stream to route audio directly from your DAW (playback streams 11-12 and 13-14)."

If you're using Logic then you need to route output to those playback streams.

If you do not know how to route output in Logic please see your reference manual for Logic.