Discovercircuits.com - a resource for engineers, hobbyists, inventors, students & consultants containing a collection of 26,000+ electronic circuits or electronic schematics cross-referenced into 550+ categories plus an extensive electronics engineering resource/reference section.

ELECTRONIC CIRCUITS - Information on Electronic Circuits, Kits and Projects, including users forums for people to share ideas

CIRCUITZ4U.COM -Circuit and pc board design services.

Top Hat Amplifiers - TopHat Amplifiers are hand built, point-to-point circuit, high performance tube amplifiers with all the tone imaginable

Vintone Circuits -

Tatoo Amplification - Amplifiers one at a time by hand, High quality components used throughout, Custom wound transformers, All tube: no clipping diodes or integrated circuits, Tag board construction, simple circuitry, high reliability and maximum tone!