Watford Valves Valves and other components for your amp.
Tube Amp Doctor Everything you need for your amp.
Modulus Amplification Components, cabs and kits for valve amps.
Marshall Amplification Yes, we supply Marshall with their transformers, but we don't supply spares. Please contact Marshall directly.
Root-Two Very experienced ex Marshall design engineer who can repair or modify your amplifier
DIY Audio An excellent forum, with projects, circuit diagrams and lots of advice
AX84 Another great site, tons of information, projects and kits, and a busy forum.
The Valve Wizard Merlin Blencowe's website is packed with useful information for valve amp designers.
Duncan Amp Pages Lots of technical data, schematics, SPICE models.