You cannot use a headamp by itself with the Stellar preamp as you also need a phono stage that will provide additional gain and RIAA equalization. Headamps are designed to plug into Phono inputs and that preamp only offers line inputs.
Thanks, it is also what I see. The manual however states:
“..while the XLR connector delivers a balanced signal to compatible inputs. Both can be connected at the same time, allowing one to drive a power amplifier and the other, a subwoofer or headphone amplifier, for example..”
What you are trying to connect is a headphone amp not a headamp. A headamp is designed to interface a low output MC phono cartridge to a MM phono input of a preamp. I am afraid there is no way to avoid the dual controls except by paralleling the music source component and bypassing the preamp.
I would not be concerned as lone as you set the controls so there is sufficient range in the headphone amp’s. The sonic impact is easy to evaluate by simply running your source directly to the amp. If you don’t hear a negative difference once level-matched you’re fine. Depending on the headphone amp’s design and whether its volume control is input buffered, you may fine the preamp combo sounds better,