Misc audio (also see Music, Amplifiers, Preamp)

  • Electronic siren
  • Two-tone siren
  • Underwater microphone
  • Code practice oscillator
  • Noise generator
  • Electronic whistle
  • Twin-T Audio Sine Wave Oscillator
  • 1.5V Audio Amplifier
  • Low Power Op-Amp - Audio Amp (Intercom)
  • 555 Tone Generator (8 Ohm Speaker)
  • 3 Transistor Audio Amp (50 milliwatt)
  • Low Frequency Sinewave Generator
  • Automatic Charger for Battery Operated Hi-Fi Preamps
  • Audio level indicator
  • Room noise detector
  • Amplifier timer
  • Bell ring generator
  • Amplified ear
  • Precision audio millivoltmeter
  • Six-channel Mixer and Amplifier
  • Audio Signal Source
  • Analog VU meter
  • Voltage controlled amplifier
  • Audio graphic equaliser
  • Intercom preamp
  • FET audio mixer
  • Microphone mixer
  • Tone control
  • Digital volume control
  • Sound level meter
  • Three band Active Tone Control
  • Automatic gain control (AGC) circuits
  • Audio frequency meter
  • Bull Horn
  • Sound Mixer/Amplifier
  • Very loud beeper (PDF)
  • Digital noise generator (PDF)
  • Tone display system
  • Tube amplifier
  • Condenser microphone hookup
  • Phase shifter
  • Paradoxical Sound Syntheizer
  • Digital volume control
  • Electronic attenuator
  • Speech recorded using ISD2560
  • Precision audio millivoltmeter
  • Automatic loudness control
  • Three channel audio spectrum analyzer
  • Base / treble control circuit using LM1036N
  • Cuckoo sound generator
  • Room noise detector
  • Various tube crossover circuits
  • Bias circuits
  • Audio line isolator
  • Dynamic microphone to electret microphone input
  • Line level signal to microphone input adapter
  • Simple two line output combiner
  • Electret microphone powering circuits
  • Use amplifier phono input as line level input
  • Speaker signals to line level inputs
  • Spring reverb unit
  • Sine wave generator
  • Simple amplifier
  • 3-Band equalizer
  • 6-Input mixer
  • Doorphone intercom
  • Stereo line driver
  • Audio notch filer
  • Peak reading audio level meter
  • Tone control
  • Speaker Microphone Circuit
  • Electronic canary
  • Electronic siren
  • Microphone phantom power supply
  • Voltage Controlled Mixer w/Modulator
  • Dual Voltage Controlled Oscillator w/Modulator
  • Dual Voltage Controlled Filter w/Modulator
  • Stereo Ducker
  • MS Stereo Decoder
  • MS Stereo Microphone
  • RIAA Equalized Stereo Phono Preamp
  • Tube active crossover
  • Improved PL tone decoder
  • Magnetic cartridge amplifier
  • LM358 preamp
  • Sound detector
  • Tone detector
  • Tone generator
  • Warbler
  • Voltage Controlled Panner
  • Low Noise Microphone Preamplifier
  • Bridging Adapter For Power Amplifiers
  • Simple Surround Sound Decoder
  • Simplest Ever Amplifier Bridging
  • Stereo Width Controllers
  • Power Amplifier Clipping Indicator
  • Phono Preamps For All
  • Digital Delay Unit For Surround Sound
  • Parametric And Sub-Woofer Equaliser
  • High Quality Sound Mixer
  • Loudspeaker Protection and Muting
  • Direct Injection Box for Recording & PA Systems
  • Minimalist Discrete Hi-Fi Preamp
  • Signal Detecting Auto Power-On Unit
  • Load Sensing Automatic Switch
  • Amplifier thermal protection
  • Active Sub-Woofer and Controller
  • Balanced Line Driver & Receiver
  • VU And PPM Audio Metering
  • Variable Amplifier Impedance
  • Linkwitz Cosine Burst Generator
  • Low Noise Balanced Microphone Preamp
  • Fast Audio Peak Limiter
  • Subwoofer Equaliser
  • Surround Sound Decoder Mk2
  • Audio mixer