RED Free Circuit Designs - Audio

Audio Circuits

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Fasteners & Fixing Elements	Audio Mini-MosFet Audio Amplifier Including Preamp, Tone Controls and Regulated dc PS 18 Watt into 8 Ohm - 30W into 4 Ohm loads 18 Watt Audio Amplifier High Quality very simple unit No need for a preamplifier 25 Watt MosFet Audio Amplifier High Quality simple design No need for a preamplifier 60 Watt MosFet Audio Amplifier High Quality, powerful unit: 90W into 4 Ohm Also suited as guitar or bass amplifier 10W Audio Amplifier with Bass-boost High Quality, very simple design No need for a preamplifier Mini-box 2W Amplifier Designed for self-powered 8, 4 & 2 Ohm loudspeakers Bass-boost switch 3 - 5 Watt Class-A Audio Amplifier Behaves like a one-valve operated amplifier Simple circuitry - No cross-over distortion Modular Audio Preamplifier High Quality, Discrete Components Design Input and Tone Control Modules Phono Preamplifier Simple circuitry suitable for moving-magnet cartridges Passive high-frequency equalization Stereo Preamplifier with Bass-boost High Quality, simple design 20 to 30V supply Automatic Loudness Control Simple add-on module Switchable "Control-flat" option Portable Microphone Preamplifier High headroom input circuitry 9V Battery powered Headphone Amplifier High Quality unit No need for a preamplifier Portable Headphone Amplifier 3V Battery powered High Performance unit Portable Mixer High-quality modular design 9V Battery powered - Very low current drawing Three-Level Audio Power Indicator Battery-operated 3 LED display Simply connect it to loudspeaker output Six-LED Bar Power Indicator Useful to monitor audio power delivered to loudspeakers No power supply - no setup required Precision Audio Millivoltmeter Measures 10mV to 50Volt RMS in eight ranges Simply connect to your Avo-meter set @ 50µA range Sound Pressure Level Meter Suitable for home-cinema setup 9 Volt operated portable unit 1KHz Sinewave Generator Simple circuitry, low distortion, battery operated Variable, low impedance output up to 1V RMS
Award winner! Published on ELECTRONICS WORLD "Circuit Ideas" February 2003 issue, page 38	Low-distortion Audio-range Oscillator Generates very low-distortion sine waves up to 1V RMS No thermistors required - No settling time
	Simple Squarewave Generator Three switchable frequencies: 100Hz, 1KHz, 10KHz 1.5V battery operated, minimum parts counting
This circuit won £50 and was published on ELECTRONICS WORLD "Circuit Ideas" February 2000 issue, page 135	Self-powered Sine to Square wave Converter Converts sine to square waves without a power-source Useful as a test instrument for audio purposes
	Amplifier Timer Turns-off your amplifier when idle for 15 minutes Fed by amplifier tape-output Amplified Ear Useful to listen in faint sounds 1.5V Battery operation Full-duplex Intercom No complex switching required Simple circuitry, 6-12V supply Telephone call Voice Changer Voice manipulation device specially intended for props 9V Battery operation Intercom with fader Suitable for tandem bicycles and motor cycles Connects to iPod and similar MP3 audio players Mini Mixer Small portable device - 9V battery operation Three high/low-sensitivity switchable inputs Portable 9V Headphone Amplifier High Quality One-IC unit Low current consumption Speech Amplifier Box Small portable device - 6V battery operation Suitable for teachers, lecturers, tourists' guides etc. Audio Clipping Indicator Detects clipping in preamp stages, mixers, amplifiers etc. Single LED display - 9V Battery supply unit

Last updated: 6 July 2008

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