Ampex Manuals and Schematics (The Ampex Data Systems link is no longer available. Coming soon to another site)
Bell System Technical Journal (BSTJ) All isues 1922...1983 in PDF, with
author and title searches. Bell Tel Labs invented or developed much of
audio engineering as we know it, among many other things.
A Bibliography of "Must Have" Tube Electronics Books Good bibliography for the tube circuit designer from noted guitar amp builder Randall Aiken.
Hi-Fi Literature Resource for U.S. hi-fi advertising and sales literature (plus smaller professional section) from 1940-s, 50-s and 60-s.
Phonograph Makers' Pages Bare-bones site for builders of modern cylinder players.
Pro Audio Reference Books Comprehensive audio bibliography from Rane.
Reprints of Classic Books on Acoustics, Electronics, Loudspeakers, Vacuum Tubes, etc. Audio-only on-line bookshop.
Schematics for Preamplifiers, Compressors, and Limiters Extensive on-line resource for pro-audio schematics from Purple Audio.
Shure Discontinued Products PDF guide to (apparently) all Shure microphones ever manufactured, maintained by the company.
Technician's Filing Cabinet Links to schematics for consumer and professional audio, ham radio, transformers, military electronics, test equipment, and old radios.
Telefunken T9 Tape Deck Complete documentation and many color pictures of two Telefunken T9 tape machines, at one time for sale.
Tube Manuals PDF copies of GE, Matchlett and RCA books on tubes and circuit design.