| Cabasse Loudspeakers | Speakers |
| Cable Services | Braids, Tubings & Heat Shrinks |
| Cableland | Cables |
| CAD Microphones | Microphones |
| Caddock Electronics | Resistors |
| CadenceAudio | Tube Amplifiers, Speakers |
| CAIG Laboratories, Inc. | Connector Enhancing Treatments |
| Calcolo di Trasformatori | X-former Calculations, DIY Tube Amplifiers |
| California Historical Radio Society | Information about old radios |
| Campaign Audio Design | Cables |
| Canadian Communication Consortium | Broadcasting equipment |
| Canadian Hi-Fi Exquisite Used Audio | Retailer |
| Canare Corporation of America | Cables, Connectors |
| Canary Audio | Tube Amplifiers |
| Candela Valve Amplifier | Tube Amplifiers |
| Candyman Electronics | Tubes, Parts |
| Cantare Audiosysteme | Speakers |
| Cardas Audio | Cables |
| Carfrae Loudspeakers | Horn Speakers |
| Carolina TubeWorks | Tubes, Vintage Tube Audio Equipment |
| Cary Audio Design | Yahoo store |
| Cary Audio Design, Inc. | Tube Amplifiers |
| Cassiopeia - Audio Einstein | Tube Amplifiers |
| Casweb | Audiophile Society, Links |
| CATCables.com | Cables |
| Cayin | Tube Amplifiers |
| CE Distribution LLC Tube Accessories | Parts, Tubes |
| Centasound | Tube Amplifiers |
| Centro Laboratorio HI-FI | Tube Amplifiers, Parts |
| CF media | Retailers, Beard Tube Amplifiers |
| Chaffee Hickok service | Tube Tester Services |
| Charisma Audio | Retailer |
| Charles MacDonald's Electronic Tube page | Information about Tube Audio - Articles, Links |
| Chelmer Valve Company Ltd | Tubes |
| Chevet Supplies Ltd. | Vintage Tube Audio Equipment |
| Chicago Audio Society | Audio Club, links |
| Chicago Joe's Tube Information Page | Tube Databases |
| Chifiaudio | Speakers |
| Chimera Labs | Tube Amplifiers, Cables, Tubes, Vintage Audio Equipment restoration, sale |
| CHINA AVPHILE | Magazine |
| Chris and Sue's Page | DIY Tube Amplifiers |
| Chris's Tube Haven | DIY Tube Amplifiers |
| Ciare | Speakers |
| Ciel-Electronique | Tubes, Parts |
| Circlotron History Page | Tube Audio Information |
| Claritycap | Audio coupling capacitors |
| Class 330 AMPLIFIERS | U.S. Patent Classification Definitions |
| Class A High Performance | Retailer |
| Classic Amp Repair | Vintage Tube Guitar, HiFi Amplifier Service |
| Classic Audio Reproductions | Horn Loudspeakers |
| Classic Audio, Hi-Fi, Stereo, Tubes | Classic Audio, Hi-Fi, Stereo, Tubes, Speakers |
| Classic Audio, Hi-Fi, Stereo, Tubes, Speakers | Classic Audio, Hi-Fi, Stereo, Tubes, Speakers |
| Classic Components Inc. | Tubes, Japanese Parts |
| Classic H.H.Scott Pages | Information about Scott amps for collectors |
| Classic HiFi - Jochen Straceny | Tube Amplifier Services |
| Classic tube | DIY Tube Ampliers |
| Cliff Electronic Components | Connectors |
| Club l'Auditorium | Retailer |
| Coherent Classic Audio | Vacuum Tubes Retailers New and NOS Tubes |
| Coincident Speaker Technology | Speakers |
| Coleman Audio | Tube Electronics for Professionals |
| Colomor (Electronics) Ltd | Tubes |
| Colorado Audio Society | Information, Links |
| Components Express | AC Wire, Plugs & Sockets |
| Connoisseur Audio | Tube Amplifiers |
| Conrad Electronik | Retailer |
| Conrad-Johnson | Tube Electronics |
| Consonance Home | Retailer |
| Consumer Audio Information | Schematics |
| Contact East | Test Equipment |
| Conus Audio | Tubes |
| Cool Schematics | Schematics |
| Copland | Danish Tube Electronics |
| Corda Audio | Tube Amplifiers, Retailer |
| Corona AmpWorks | Tube Guitar Amplifiers |
| Cosmos Hi-Fi - El Arte | Retailer |
| Counterpoint | Upgrade and service for their Amps |
| Covimag | Tubes |
| CPI Eimac | Vacuum Tubes Manufacturers, Vacuum Tube Sockets |
| CPI Eimac Division | Tubes |
| CR Development | Tube Amplifiers |
| Crate Amplifiers | Tube Guitar Amplifiers |
| Creative Sound Solutions | Speakers |
| Croft Amplification | Tube Amplifiers |
| Crowthorne Tubes | Tubes |
| Crystal Illusion Ltd. | Two channel Tube Compressor |
| Crystal Radio The Xtal Set Society | DIY Radio Electronics |
| CUI Stack_DIGI-KEY | Switches, Transformers |
| Curcio Audio Engineering | Tube Amplifier Kits |
| Current Solutions | Power Transformers |
| Custom Speakers and Subwoofers by 3Dz Audio | Speakers |
| Cyber Workshop in Maizuru | DIY Tube Amplifiers |