Interesting Audio and Photo Equipment Schematics and Patents:

Schematics: Patents:
Adcom 555 Amplifier  
Adcom 555 Power Supply Mod  
Audio Research SP3 Preamplifier Amplifiers

Madison Fielding FM-15 Tuner 

Loudspeakers
   

Hafler DH-110 Preamplifier

 Things Photographic