I’m not entirely clear on what your signal chain is, but if you have any sources connected to the optical or digital coaxial inputs on the Yamaha, or if you’re using the wireless or wired network connectivity, then yes, the Yamaha DAC is converting the signal.
Technically I suppose you could use the headphone output as a pre-amp out of sorts, but if I needed that functionality I’d be more inclined to run a line out to a volume controller (a Schiit Sys for example) and then in to your power amp (I’m assuming here that the NAD is a power amp and you’re looking for a way to control volume). The tone controls would not be in the signal chain in that scenario.
What are you trying to achieve by using the Yamaha as a pre-amp? Do you feel that your speakers require the power of the NAD? Are you using the NAD to power speakers in another location?
Thanks for the response. I have both optical ( from TV) and digital coaxial (from CD Player) inputs on the Yamaha. Apart from this, I use my Yamaha as a DLNA endpoint to stream my music from PC over the network. I rarely use the Airplay ( mostly by my friends when they give visit ). Yamaha also got Tidal and Spotify and comes handy with a remote control which lets me swtich the inputs. Now I am planning to upgrade to an All in one device like Eversolo A6 or FiiO R7. These are expensive devices and my Yamaha can do almost the same functions except no touch screen and modern DAC.
When I connect my Yamaha directly to the speakers ( Q acoustics 3050i), I need to crank up the volume to 75% above ( around -20 to -18 ) to make my Q acoustics sing. So I added an old NAD 317 which got plenty to of power and at 20% volume, its loud enough for my room. This NAD is an intergated amps with pre and power seperation so it can act as pre-amp and power amp. I don't have remote for NAD and problem is that when I connect Yamaha via Lineout the volume control doesn't work. So I thought replacing my Yamaha with a device which got all the inputs and preamp out will work. Now considering the cost of the new device, I am okay to keep my Yamaha if the DAC is working in the lineout mode ( inputs from my TV & CD player). If the DACs are not coming into play, that will justify my reason to replace my Yamaha and if the DAC is working, I am content with the current setup. So I need your advise.
My Signal Chains :
TV Optical Out>Yamaha Optical In>Yamaha Lineout>NAD Line In>Q Acoustics
CD Coaxial Out>Yamaha Coaxial In>Yamaha Lineout>NAD Line In>Q Acoustics
From PC >Audirvana/Plex>Yamaha via Wifi>Yamaha Lineout>NAD Line In>Q Acoustics
Thanks