Audio 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

60W Guitar Amplifier

Bass, Treble, Harmonic modifier and Brightness controls. Output power: 40W into 8 Ohm and 60W into 4 Ohm loads

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.

Amp with Tone Controls & Soft Switching

Built around an LM380, this amplifier includes tone controls and electronic "soft switching". The soft switching circuitry ensures power is built up gradually eliminating the dc thump.

15 Watt Amplifier

A 15 watt amplifier made using discrete components. Sergio designed this circuit for his Electronics Level II course.

Quadraphonic Amplifier

This is a four channel amplifier ideally suited for use with quadraphonic equipment such as a Sound Blaster Live card. There is no volume control,audio levels being directly controlled from the sound card itself.

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.

Audio VU Meter

This circuit uses two quad op-amps to form an eight LED audio level meter. The op-amp used in this particular circuit is the LM324. It is a popular IC and should be available from many parts stores.