The headphone L/R RCA outputs for headphones are the same as the stereo phono jack output on the front. The A8 is acting as a preamp in this setup, with the ouptut going to a headphone amp which would also have its own volume control. And of course the A8's preamp has a digital volume control, which influences the output on the RCA and phono jacks. So you normally have TWO volume controls, and using either one will affect the volume as heard in your headphones. You will by trial and error determine what works best for you, as the default volume level to set in the A8 and the dial/digital position of your amp's volume control. I have my A8 set at -10db volume, which corresponds to a Stax SRM-007tii setting of "2 o'clock", as my own everyday normal starting volume arrangement for everything. If I want things to be louder or quieter, I always only use the dial on my Stax amp. Easier and more comfortable and more precise to just walk over to the amp and tweak the volume dial a bit, until I'm hearing at the level I want. I can't remember when I used the A8's digital volume to change it from -10. But if your amp doesn't have a volume control then I suppose the A8's will have to do.