Building the Bottlehead Crack Headphone Amplifier (Review & Impressions)
Moreplay Preamplifier kit - Bottlehead
DIY Audio Electronics from Zynsonix.com: The Bottlehead Crack OTL Headphone Amplifier
Bottlehead Corp. - Fire-Crack! From now through July 4th you can show your independence by ordering a made-in-America headphone amp kit that you build yourself. We will be transitioning to a universal