lumin direct to "main in" section on Yamahas/Luxmans/Accuphase?

The the OP as you travel on your audio journey do yourself a favor and try running the D2 USB out into a nice R2R DAC and into a tube integrated amp. You do not know what you are missing.

As a Lumin D2 owner (in the box up for sale) I can tell you that the internal DAC is a little harsh sounding with many amps and running it straight into a power amp is not going to sound the best.

But to each his own. I have gotten to the point where I cannot even listen to solid state anything anymore without getting very angry and smashing the speakers....😀

Just make sure you have the Lumin's Leedh volume control activated (variable output) and start on the lowest level setting to be safe. Using a good preamp sounds better to many listeners, but there should be no problem in using the Lumin's variable output into an amplifier directly.

But to each his own. I have gotten to the point where I cannot even listen to solid state anything anymore without getting very angry and smashing the speakers....😀

Umm... I’m not sure if that’s the fault of solid-state amplifiers. Harshness can be associated with many things - speakers, amp-speaker interface, source or room, or a combination of any.