Category «Audio»

Sound-Controlled Relay

This is a relay circuit that detect the presence of sound to activate the relay. You can use this sound-controlled relay as voice operated switch, light control, toys, or any other application that can be controlled by a switch. Just replace the switch with  this relay and now you have a sound-controlled device. This circuit …

Optical Theremin

Normally, Theremin works by detecting hand proximity using capacitive coupling method. A Theremin circuit shown in the schematic diagram below use different method to control the pitch. The oscillator of this tone generator, both the volume and frequency  are controlled using LDRs, a light sensitive electronic component, so we can call this circuit an optical …

Simple Digital Theremin

Theremin circuit shown in this schematic diagram uses digital component, so we can call it a digital Theremin. This circuit employs  logic inverter 74C04 or CD4069 hex inverter and CD4046 phase-locked-loop (PLL) IC. The CD4069 logic inverter is operated as a fixed-frequency oscillator with  frequency around 100kHz. The CD4046 is operated as a variable frequency …

Single Chip Theremin Circuit

This schematic diagram show a single chip Theremin circuit.  Theremin is an electronic music instrument which sense hand movement to control the tones/frequency.  This Theremin circuit uses two separate Colpitts LC oscillators to produce a beat frequency. The frequencies of  two Colpitts LC oscillators are mixed and then rectified. This rectification  demodulate the mixed signal …

22W Amplifier for 12V Power Supply Systems

This is a 22-W Amplifier circuit that is designed for or 12-V DC power supply Systems. There are many application for  this circuit,  such as in car audio  application. In car electrical  power supply system, the 12V power supply will be provided by the host vehicle’s battery. The capacitor C3 is used to give ripple …

Funk (Twang) Guitar Effect Box

This is an audio effect circuit that give extra oscillation to your guitar, percussive, or semi percussive instruments, you can call it a funk box. This  guitar effect circuit is basically a damped oscillator that is set slightly below its critical oscillation point.  The oscillator part is constructed by feeding back the output signal through …

Audio Power Amplifier for AM Radio

This is an AM radio power amplifier circuit. What is different with other general amplifier is that this circuit has a low-pass filter (passive type), built using R1C1 to limit the input-output frequency response. Additionally, a ferroxcube K5-001-001/3B with 3 turns of wire is used as ferrite bead  at output filter. All components should be …