Tubes are big at the fest, even tiny ones. Single Power's Mikhail Rotenberg was proud of his $1200 Mini, which is an order of magnitude smaller than his usual gear. Single Power is the Duesenberg of headphone amps—the gear is impeccably built, impressively powerful, and almost complete bespoke. While Rotenberg offers "models," he usually consults closely with customers, refining his designs to meet their needs.