schiit sys in a nut shell Sys is a simple, 2-input passive preamp. No electronics. No power. No distortion. Just a 2-way switch and a potentiometer.   what is a potentiometer you say this can tell...

its a pre amp you still need a headphone amp ex im planing on a stack with sys and vali  its a pre amp you still need a headphone amp ex: im planing on a stack with sys and vali. so it would make the vali perform better thus making the headphones perform better

im looking at the beyerdynamic custom one pro and beyerdynamic dt770 250 ohms pro http://www.amazon.com/gp/product/B008XEYT48/ref=ox_sc_act_title_4?ie=UTF8&psc=1&smid=ATVPDKIKX0DER http://www.amazon.com/gp/product/B0006NL5SM/ref=ox_sc_act_title_2?ie=UTF8&psc=1&smid=A304D686EJ3MRJ im not sure...