There are 37 circuit schematics available. Last circuit added on Tuesday, 19 May 2015.

CircuitCategoryDate AddedOK?
Bat detector microphone pre-amplifiersPreamp 
Voltage follower with 1G ohm input resistance based on LM11 opampPreampOct 21, 2009
Low impedance microphone amplifierPreampMar 23, 2003
General purchase audio preamplifier based on pair of 2N2222 transistorsPreampJan 31, 2010
Magentic phono cartridge phono preamp circuit diagramPreampFeb 05, 2010
Selection of audio preamplifiers including circuits suitable for battery operationPreampJan 31, 2010
IC tone control preamplifier using single 741 opampPreampJul 03, 2011
Two transistor audio preamplifier with volume controlPreampJul 03, 2011
Basic logarithmic amplifier using op-amp and NPN transistorPreampJul 03, 2011
Low voltage microphone preamplifier using LM10PreampMay 25, 2012
Mono audio preamplifier using single 2SC732 transistorPreampMay 25, 2012
Low Noise Microphone PreamplifierPreampJun 04, 2010
Collection of phono preamplifier circuitsPreampApr 21, 2010
Simple Car Preamplifier and Artificial EarthPreampJan 29, 2010
High quality audio preamplifier (OPA2134)PreampSep 13, 2006
Basic low frequency preamplifier circuitsPreamp 
Microphone pre-amp with high emphasisPreamp 
Microphone preamp for portable transceiversPreamp 
Intercom preampPreampAug 12, 2001
Simple microphone preamplifierPreampJan 26, 2001
Simple microphone preamplifierPreampJan 26, 2001
Hi-Fi Preamp with remote-control and other advanced featuresPreamp 
Balanced microphone preampPreampNov 01, 2002
Electret mic amplifierPreampJan 26, 2001
Audio preamplifierPreampJan 26, 2001
Audio preampPreampJan 26, 2001
Vacuum Tube Microphone PreampPreampNov 01, 2002
FET Preamp CablePreampNov 01, 2002
Altec 1564A Preamp Power SupplyPreampSep 13, 2006
Neumann U67 microphone preamp power supplyPreampSep 13, 2006
Altec 428B Microphone Preamplifier schematicPreampSep 13, 2006
API 321 mic preamp schematicPreampSep 13, 2006
RCA BA-1A two-stage preamp schematicPreampSep 13, 2006
RCA BA-21A preamplifier schematicPreampSep 13, 2006
RCA BA-31A preamplifier schematicPreampSep 13, 2006
ECM Mic preampPreampJan 26, 2001
Hi Fi preampPreampJan 26, 2001