(Jotunheim stacked with a Modi 2 multibit, lurking on the desktop)       Preamble Schiit Audio are the darlings of the affordable head-fi world. Their line-up of amps and DACs run from the tiny and budget (Fulla, Magni) to "serious" kit like the Yggdrasil, which is arguably the equal to competitors many times the price.   They're remarkably straightforward about specs and performance, and unlike some manufacturers steer clear of the more fanciful claims of outright audiofoolery. While they've had a few duff efforts (the notorious early Lyr...