Martin's links

Electronics

Amplifier

NTE Cross Reference Search

Simple LM386 Amplifier (Japan)

Circuits for the Hobbyist

Microphone Preamp a la PAiA

Headphone Amp

General Purpose 2 x 2Watts Power Amplifier (TBA820 or NTE1117 OpAmp)

http://www.nteinc.com/specs/1200to1299/pdf/nte1294.pdf

Peak Reading Audio Level Meter

LM741 OpAmp Amplifier (Bob Blick)

HeadBanger Headphone Amp