I'm no digital audio expert. I have managed to avoid it for the most part and only plug into the digits for convenience. Tinkering with filters sounds interesting. When I have the time I'll read up on it. There are a whole lot of bunches of albums here and a couple short of 800 CDs. You get the picture. I have spent a few evenings with my ancient SR71 plugged in between the Kann and the Etymotics. All is well, the resonance missing with the internal amp is back. Same results using the Holmes Powell amp and Grado HP-2s. Thoughts?