Preamplifiers circuit diagrams

ECM Mic Preamplifier

A microphone amplifier that may be used with either Electret Condenser Microphone (ECM) inserts or dynamic inserts, made with discrete components.

Guitar Control

Stand-alone, 9V battery powered unit. Three-level input selector, three-band tone control

Computer Microphone

This circuit was submitted by Lazar Pancic from Yugoslavia. The sound card for a PC generally has a microphone input, speaker output and sometimes line inputs and outputs. The mic input is designed for dynamic microphones only in impedance range of 200 to 600 ohms.

Room Monitor

This circuit allows audio monitoring of a remote location and so doubles as a room monitor or baby alarm.

Speaker Mic Circuit

This circuit takes an ordinary loudspeaker and allows it to be used in reverse, as a microphone.

Guitar Preamp with Tone Controls

An electric guitar pre-amp with tone controls using dual supplies. The guitar pickup is high impedance, therefore good quality screened cable must be used between guitar pickup and the preamp.

Hi-Fi Preamplifier

This circuit has an exceptionally fast high frequency response,as demonstrated by applying an 100kHz squarewave to the input.

Low Voltage Preamplifier

A low voltage preamplifier optimized for 3 Volt operation.

Dynamic Microphone Preamp

A low noise pre-amplifier suitable for amplifying dynamic microphones with 200 to 600 ohm output impedance.

Op-Amp Mic Preamp

A high quality microphone preamplifier using a single power supply, suitable for dynamic or electret microphones. The op-amp used can be any low noise, high performance type, e.g. NE5534,TL071, OPA 371 etc.