Just wanted to emphasize, that the thread above is mainly a showcase thread, intended as a starting point for further personal research. Information like price-ranges, manufacturing countries, and relevants links have been added to facilitate this research.
As already mentioned the thread includes tube headphone amplifiers from around the world: Australia, Canada, China, Croatia, France, Germany, Greece, Italy, Japan, Latvia, Netherlands, Poland, Russia, Serbia, Slovakia, South Korea, Sweden, Thailand, UK, USA.
And the following brands/manufacturers are represented: Abin Audio, Analog Design Labs, Allnic Audio, ALO Audio, Analog Squared Paper, Antique Sound Lab, Apex Hi-Fi, ARG.audio, Arkhipov's Laboratory, Audio Note, Audio Research, Audio Space, Audio-Technica, AudioValve, Aune Audio, Auris Audio, Autocostruire, Bacchus Antiques, Bottlehead, Bravo, Brocksieper, Canor Audio, Cary Audio, Cavalli Audio, Cayin Audio, Clinamen Audio, Coffman Labs, Custom Hifi Cables, Dared Audio, David Berning, Decware, DIYHiFiSupply, Doge Audio, Donald North Audio, Dubiel Acoustics, EAR Yoshino, ECP Audio, Eddie Current, Elekit, Ele System Industry, Emillé Labs, EternalArts, Finale Audio, Flux Lab Acoustics, G&W Tsinghua, Garage1217, GPinto, Grant Fidelity, HAD Audiolab, Halgorythme, HeadAmp Audio, HiFiMAN, Icon Audio, Jasmine Audio, Jolida, Kasuga, KingSound, Kypo, Lab12, Labtek, Laconic Lab, Leben Hi-Fi, Line Magnetic Audio, Little Dot, Luxman, MalValve, Manley, Mapletree Audio Design, Maverick Audio, McAlister Audio, McChanson, Megahertz Audio, Mexing, Mistral Audio, Music Hall Audio, Musical Paradise, Musical Surroundings, NixieKits, Opera Consonance, Orphean Sound, Ortofon, Pathos Acoustics, Peachtree Audio, Raphaelite Sinovt, Ray Samuels Audio, Red Wine Audio, Rolls Corporation, Röcklinger, Rudistor Sound Systems, SAC Thailand, Schiit Audio, Sense Audio, S.I. Audio, Solaja Audio, Space-Tech Laboratory, TPaudio, Tektron, Trafomatic Audio, Triode Corporation, Vexo HiFi, Virgil Laboratories, Vincent, White Bird Amplification, Woo Audio, Xindak, Yamamoto Sound Craft, Yarland Audio, Yu Qin Audio, Zigis Audio Lab