| H.J. Leak & Co. Ltd | Forum |
| L A T International, Inc. | Cables |
| L.A. Music Distribution | Retailer |
| La Hifi High End DIY | DIY Tube Amplifiers |
| LABTEK | Tube Amplifiers |
| Lamm Industries | Tube Amplifiers |
| Lamphear Electronics | Tube Amplifiers |
| Lampy Elektro-nowe | Transformers, Schematics |
| Lancroft Audio Transformers | Tube Amplifiers, Transformers |
| Lansing Heritage | James Bullough Lansing and his products |
| L'ATOUT Highend products | Retailer |
| Lautsprecher -Bau-Kunst LA DIVINA MUSICA! | Speakers, Retailer |
| Lautsprecherselbstbau | Speakers, Speaker Kits, Information |
| Lawson Microphones--Relive the Magic | Tube Microphones |
| Le Radio di Sophie | Tube Radios & Related Vintage Items |
| Leader USA | Test Instruments |
| Leak | All about Leak and Lowther Amplification |
| Leben | Tube Amplifiers |
| LeBong Audio Retro Audio Konzepte | DIY Tube Amplifiers |
| Lector Audio | Tube Amplifer Kits |
| Lee Jackson Audio | Tube Guitar Amplifiers |
| Lee Jaehong 6C33C OTL | Schematic, DIY Tube Amplifier |
| Leeds & Northrup | Tube Type Amplifier for Measurements |
| Leeds Electronics | Tubes and Parts |
| Legend | DIY Tube Amplifiers |
| Legend Audio | Tube Amplifiers |
| LEO Instruments | Tube Amplifiers |
| Leo Research | Tube Amplifiers |
| LH-musik index | Tubes, Parts |
| Lidstrom Audio | Information, Schematics |
| Lighthouse Electric | Tube Amplifier Kits |
| Lin Robertson's Old-Time Radio Page | Vintage Tube Audio Equipment |
| Little Lanilei Tube Amplifier™ by Songworks Systems & Products, USA | Tube Guitar Amplifiers |
| Living Voice | Speakers |
| London Live DIY HiFi Circle | DIY Audio, Thorsten Loesch, George Brook |
| London Power Amplifiers | Tube Amplifier Kits and Books for Musicians |
| Longan | Tube Amplifiers |
| Lord Valve NBS Electronics | Tubes |
| Losonci | Tubes, Tube Amplifiers |
| Losonci Tubes | JJ Electronic Tubes |
| Loth X by Ossaudio | Speakers |
| Loudspeaker | DIY Speaker |
| Loudspeakers.de | German speaker site |
| Low Power Radio | Tube Electronics for Professionals, AM Transmitter |
| Löwenkatapult | DIY Tube Amplifiers, Link Lists |
| Löwenkatapult.de | DIY Tube Amplifiers, Link Lists |
| Lowther | Speakers |
| Lowther America | All about Lowther Speakers |
| Lowther Club Hongkong | Speakers |
| Lowther Speakers USA | Sell and gives good Information about Lowther |
| Lua | Tube Amplifiers, Speakers |
| Lucas Engineering | High end professional audio equipment |
| Lumley by Sounds of Music | Tube Amplifiers (Lumley) |
| Lundahl Transformers | Fine Swedish Transformer Company |
| Luxman Corporation | Tube Amplifiers |
| Lyn-Tron, Inc | Standoffs, Screws |
| Lynx Audio - Valve Amplification | Tube Guitar Amplifiers, Transformers |