"Attachment scheme" is a convoluted trick whereby you plug in a "dummy" 3.5mm device (like the impedance adapter jack or a short 3.5mm extension cord) when music is selected so that the phone's audio output thinks the load is "infinite", thereby triggering the HQ output in the quad DAC. Then, when you plug in your low-impedance 'phones the HQ output thinks it's actually hooked to a high-impedance device. Lots of folk just keep the little impedance adapter jack in all the time, but for some power-hungry 'phones it reduces available volume. Or not (YMMV). Search this entire thread for other good tricks - and even more on the V30 thread!