Aaholm audio pages (Very nice DIY pages with projects, schematics, formulas, etc).
Andrew Huculak (Vacuum Tube Audio Gallery).
Atma-Sphere Owner's Group (Very nice OTL amplifiers).
Audio Analogue unofficial WWW page (To have a better technical understanding of some the Audio Analogue's products).
Audio Genesis (Where true Hi-Fi begins).
Bob. D.'s projects (design details of some very nice tube amplifiers).
Claudio Bonavolta's audio main Page (Lots on audio electronics, nice stuff in there!).
Cuno's homepage (About the building of his Ariel speakers (in Dutch)).
Dan Hildebrands tube gear (The tube gear which drivers a beautiful speaker).
Dennis R. Grimwood's pages (Tube collector and Audiophile).
Direct Heated Rob's page (It's all about that good old vacuum-tube).
DIYaudio (pages made for diY-ers of audio components).
Direct Heating (Mister Sakuma's very interesting view on tube audio).
Ed Billeci (devoted to fringe, ultra-fi audio bizarre).
Emission Lab Home page (Great tube and amp gallery!!).
Esoteric audio design (Andrea Ciuffoli, his 6C33B OTL and more).
Fidelis Audio Company (Peter Russell, audio guru).
Firebottle audio (The Tubular Sounds of Hollow State Technology (good one, red.)).
Frank's Electron tube Pages (Lots of information a datasheets).
FriHu's glühende Leidenschaft (Nice schematics and stuff, in German language).
Guitar tube amps (tons of guitar's sound amplification related theory & tons of schematics).
Jan's pages (Ham radio and his audio projects).
JenzA'z HiFi linkZ (A very big list with links to many pages!).
Jim de Kort (another dutch DHT lover, great pages!).
Jim's ST-70 Page (The Dynaco ST-70 inside out).
Junji Kouchi Home Page (A plainly woven presentation of tube amplifiers and music sources for the music lovers).
Kevin Kennedy (Vacuum Tube Audio Web Page).
Michel Paquette (Horns, Tango, tubes and what to do with them).
Nostalgia Air (Vintage Radio References, great information).
Nuance & Fluence (Nice pages, including reports of visits to audio lovers all over the world).
Quad world (WWW-pages dedicated to vintage Quad hifi).
SDS labs DAC page (The ideal combination of analoge and digital).
Setiawan Audio Pages (Indonesian Tube Audio Page (also English language)).
Technological fossils (Tom's collection of those golden oldies, very nice stuff for sale also).
Thomas Dunker's audio pages (Pictures and text on his beautiful amps).
The Triode Guild (Very great pages on very tube-end audio).
Tubes to go! (A real reference list).
Vacuum Tube Hi-Fi Audio (A Dutch page with a very good looking tube amp).
Wim's hybrid amp (Description of a hybrid amplifier using an interstage).