Hey there, I have a Musical Fidelity VDAC II that I feed my main system with. I use a Chromecast with an HDMI optical audio extractor as my source (I've done A/B between this setup and a Chromecast Audio with optical out and found no difference) At any rate, I stream TIDAL HiFi to the system with my iPhone and was wondering what the output level in the app should be. I had assumed about 50 percent, but then an engineer friend said you should always have it at full volume if using optical output to an external DAC. Can somebody chime in on this? thanks!