The Bottlehead Crack is not the most technically proficient headphone amplifier in its price range, but for this reviewer it is among the most enjoyable. I gave the Crack a thorough listen and what follows are my thoughts, and of course the best collection of Crack cracks I can muster. I am referring, of course, to the Bottlehead Crack tube headphone amplifier kit this unit including the Speedball upgrade. So, when a HiFiGuides Forum member messaged me and said – and I’m paraphrasing here – “Hey, you wanna hear the sounds that come out of my Crack?” I thought that sounds like a gas! and immediately agreed. Those second order harmonics can be oh-so-sweet at times. There’s just something about tubes, right? By my count I either currently own or have owned 7 vacuum tubed audio products a Douk branded tube buffer, Loxjie P20, Darkvoice 336SE, Monolith Liquid Platinum, Eddie Current ZDT Jr., Cayin HA-1AMK2, and Schiit Saga. NOTE: This review was originally published on HiFiGuides forum on.