| M.M. Newman | Tools |
| MachMat's analogica | Tubes, DIY Tube Amplifier |
| Mackie Designs! | Speakers |
| Mactone Corp. | OTL Tube Amplifiers from Japan |
| Madisound Speakers No-Frames Main Menu | Speakers and Components |
| Mafrand | DIY Tube Amplifiers, Speakers, Tubes |
| Magic Parts | Tubes |
| Magnatone | Tube Guitar Amplifiers, Museum |
| Magnatone The Unofficial Ampsite | Schematics, Tube Guitar Amplifiers |
| MagneQuest | Output Transformers |
| Magnet Technology Corporation | Tube Preamplifiers |
| Magnetic SA | Transformers, DIY Tube Amplifiers |
| Main Electronics Receiving Tube Page | Tubes, Parts |
| mainecoon.com | Information about Tube Audio - Articles |
| Majestic Transformer Co. | Transformers |
| Mako Amplification | Tube Guitar Amplifiers |
| Maltzahn | Tube Amplifiers |
| Malvalve | Tube Amplifiers, Tube DACs |
| Manfred's tube audio homepage | DIY Tube Amplifier |
| Manger | Speakers |
| Manley Labs | Tube Amplifiers |
| ManualMan | Service Manuals |
| Maple Audio Works | Cables |
| Mapletree Audio Design | Tube Amplifier Kits |
| Maplin Electronics | Parts |
| Marble amplifiers | Tube Guitar Amplifiers |
| Marchand Electronics Inc. | Tube Crossover |
| Marco Pedd | DIY Tube Amplifiers |
| Margules Audio | Tube Amplifiers, Speakers |
| Marine Ode | Tubes |
| Mark Electronics | Parts |
| Markaudio | Speakers |
| Marsh Sound Design | Tube Preamplifiers |
| Marsh Tubes and Amplifier Service | Tube Amplifier Kits, Tube Amplifier Service |
| Marshal Electronics, Inc. | Connectors, Cables, Tube Microphones |
| Marshall | Tube Amplifies for Musicians |
| Marshall Arts | Information about Tube Guitar Amplifiers |
| Marshall Transformer Codes | Information about Tube Audio - Articles, Schematics, Manuals |
| Mart | Tube Electronics for Professionals |
| Martinelli Sound | Wood Horn Speakers |
| Martion Audiosysteme | Speakers |
| MarVac Home | Parts |
| Mastersound | Tube Amplifiers |
| Matamp | Tube Guitar Amplifiers |
| Mathes Amplification | Vintage Guitar Amplifiers and Repairs |
| Matisse Audio On-Line - Valve Hifi Sound Technology | Tube Amplifiers |
| Matsumoto Densi Buhin Co.Ltd | Tube Radios & Related Vintage Items |
| Matt Munyon's page | DIY Tube Audio |
| Matthias Brennwald's Homepage | DIY Tube Amplifiers |
| Matthias Schündler,High End,Tubes,Hornlautsprecher | Links |
| Matunami | DIY Tube Amplifiers |
| Mauritron Technical Services | Service and Repair Manuals |
| MAX heaDrOOM's modding island | DIY Tube Amplifiers |
| Maxfield & Montrose Interactive Inc. | Magazines |
| Maxi-Test Company | Digital Tube Tester |
| Maysyst Ltd. | Tube Amplifiers |
| McAlister Audio | Tube Amplifiers |
| McIntosh The Great American Powerhouse | Tube Amplifiers |
| MCM Electronics | Various Electronic Parts |
| Media Concepts | Books, Links, Tubes |
| MeiXing Electronic factory | Tube Amplifiers |
| Melbourne Audio Club Inc. | Audio Club |
| Melody Valve Hi-Fi Pty Ltd | Tube Amplifiers |
| MELOS AUDIO Restoration | Tube Amplifier Service |
| Memory Protection Devices Inc. | Fuse Holders |
| Memory Protection Devices Inc. MPD | Connectors |
| Mercenary Audio | Retailer |
| Meritek Electronic Corporation | Parts |
| Merithian | Heat Shrink Products and Wiring Accessories |
| Merlin Music Systems Inc. | Speakers |
| Mesa Boogie Amplifier Company | Tube Amplifiers for HiFi and Musicians |
| Messenger | Tube Preamplifiers |
| Meta-Gizmo THE NEW HOME OF THE TRIODE GUILD | The triode Guild of Dr. Gizmo |
| Metaltronix Amplifiers | Tube Guitar Amplifiers |
| Metco Electronics | Parts |
| Metha Research | Tube Amplifier |
| MF-Electronic | Tube Amplifiers |
| Michael Audio | Tubes, Vintage Tube Audio Equipment, Retailer |
| Michael Christ | Horn Speakers |
| Michael's Homepage | DIY Tube Audio |
| Michael's Radio Page | Tube Radios & Related Vintage Items |
| Michael's Village Music | Tube Amplifier Service, Vintage Tube Audio Equipment |
| Micro Components | Car Tube Amplifiers |
| Microcom Technologies | Tubes, Parts |
| Micronetics NOS Tubes | Tubes |
| Midwest Audio | Tube Amplifiers, Cables |
| Midwest Audiofest! Lima, Ohio | Fairs |
| Mighty Physics Page | Information about Tube Audio - Articles |
| Mike Boldin's Tube Amp Page | Links |
| Mike's Electric Stuff | Tube Audio Information |
| Mike's Old Vacuum Tubes | Tubes |
| Mike's tube amp pages | DIY Tube Amplifier |
| Mikkel Corydon Simonsens | DIY Tube Amplifiers |
| Milbert Amplifiers | Tube Amplifiers for Cars, Tube X-Over |
| Mill Hill Creations | Tube Guitar Amplifiers |
| Millennia Music & Media Systems | Music & Media Systems, Tube Mic Preamp |
| Minervaradio Austria | Museum |
| MiniMax-audio | Tube Amplifiers |
| mini-radios | Midget Radios |
| Minute Man | Parts |
| MITA International | Musical Instrument Technicians Association |
| Mobile Guitar Support - Guitar and Amplifier Expert Repairs | Tube Guitar Amplifier Service, Repair |
| Möhrenbude | DIY Tube Amplifiers, DIY Tube Audio Sites |
| Mojo | Tubes, Tube Guitar Amplifier Parts |
| Monarchy Audio | Tube Amplifiers |
| Mons Audio | Tube Amplifiers |
| Moody Tools | Tools |
| Moondog Audio | Tube Amplifier Kits, Speakers |
| Mor Kai Electron | Tube Amplifiers, Speakers |
| Moriyama | DIY Tube Amplifier |
| Morrow Audio | Tube Amplifiers |
| MOSweb online | Articles |
| MT Audio Design | DIY Tube Amplifiers and Quad gear |
| Mundorf-Online | Parts not only for speakers |
| Music and Guitars and Amps, Oh My! | Links, Information |
| Music Electronics µArchive | Schematics, Information, Links |
| MUSIC META-BRAIN WRESTLING RINGS | Gizmo Forum |
| Music Technology | Tube Amplifier Service |
| Music Valve Electronics | Tube Electronics for Professionals |
| musica-hifi.de | Tubes, Speakers |
| Musical Concepts-Musical Design | Tube Preamplifiers |
| Musical Fidelity | Tube Amplifiers and Electronics |
| Musical Technology by Bouke Seelemijer Audio | Tube Amplifiers |
| Musicconnection | More Fidelity: Tube Amplifiers, Speakers |
| Musiclink | Links |
| MXL Mics | Tube Microphones |
| My 2a3 Amplifier | DIY Tube Amplifier |
| My Fender Super Reverb Project | DIY Tube Audio Site |
| My Hobby | Personal Audio Site |
| My Homebrewed Vintage Amplifiers Journal | DIY Tube Amplifier |
| My tube amplifier project | DIY Tube Amplifiers |
| My Tube Stuff | DIY Tube Amplifiers |