Cassette Recorder:  (schematic added 10/06)

Cd ROM Drive as Digital Audio CD Player:  (electronic Circuit / Schematic added 10/04)

CD/DVD Drive:  Intersil Application Block Diagram  (app note added 6/06)

Color Organ #1:  make different colored bulbs light at different frequencies of music, connects to speaker outputs (added 4/02)

Color Organ #3:  makes3 Light to blink and flash to music (added 4/02)

Color Organ Circuit:  (electronic circuit added 10/06)

Color Organ Light :  This circuit works REALLY well. Notice how it will fire even in complete silence. This provides a sort of automatic gain control.   (added 2/05)

Color Organ:  I have had many requests for this circuit. It was a very popular unit years ago. The basic idea of the project is to make different colored bulbs light at different frequencies of music. The circuit connects to the speaker outputs of your stereo or to the back of your speaker. The music passes through the transformer and the volume level is adjusted by the 5k ohm pot. Each light bulb is turn on by a different frequency of sound based on the resistor & capacitor combination in the gate circuit of the SCR. If the resistors R1, R2, or R3 are changed, the frequency of sound that will trigger the SCR will change. The isolation transformer is for protection. (added 09/05)

Colour (Sound) Organ:  (electronic circuit added 4/05)

Compressor using photoresistor:  This design has a few things that make it stand out as a typical beginner's design, but I remember it worked amazingly well. I plugged an electric bass into it and I could pluck a string, put down the bass, and walk away and come back 15 minutes later with the note still playing. Finger and fret noises jumped out while hard-played notes  were crushed into submission.... (circuit design added 7/06)

Condenser microphone hookup:  (circuit diagram added 2/07)

Connect Line-Level Signal to Phono Input :  The circuit does two functions: signal level attenuation and inverse RIAA filtering. The signal attenuation is needed to convert the 500 mV signal to 2.5 mV signal. The inverse-RIAA filtering is needed to make the frequency response of the system flat (same equalization that is used when music is transferred to vinyl in the studio). The picture blow shows the frequency response of the ideal inverse-RIAA filter (added 11/05)

Connecting Speaker Signals to Line Level Inputs:  The circuit is designed to work with typical HIFI amplifiers where negative speaker connector (black) is connected to amplifier ground. Be careful here because some modern amps have both terminals actively driven. Connecting either one to a common reference could cause the output stage to smoke....  (added 11/05)

DC Fault Protection Circuit for Audio Amplifiers:  Circuit ideas how to replace traditional CD protection relays with MOSFETs (added 4/02)

Design Makes Handy Audible Circuit Tracer:  01/09/03 EDN Design Ideas  /  (added 1/05)  The circuit tracer in Figure 1 is a handy tool for finding connectivity paths on a pc board. Because the sense voltage you use to measure the path is lower than a transistor's VBE voltage, you can use the design in circuits containing semiconductor elements without affecting the measurement. The tracer's output takes the form of audio tones....

Digital Delay Unit For Surround Sound:  (diagram added 2/07)

Digital noise generator (PDF):  (electronic circuit added 2/07)

Digital Projector:  Intersil Application Block Diagram  (app note added 6/06)

Digital volume control:  (circuit diagram added 1/07)

Direct Injection Box for Recording and Psystems:  passive and active DI-box designs (added 4/02)

Distortion Analyser:  (electronic circuit added 7/03)

Distortion Analyzer:  (schematic / circuit added 10/06)

Distortion Plus:  (schematic added 10/06)

Doorphone intercom:  (schematic / circuit added 2/07)

Dual Voltage Controlled Filter w/Modulator:  (schematic / circuit added 2/07)

Dual Voltage Controlled Oscillator w/Modulator:  (schematic diagram added 2/07)

DVD Recorder:  Intersil Application Block Diagram  (app note added 6/06)

Dynamic microphone to electret microphone input:  (circuit diagram added 2/07)

Electret microphone powering circuits:  (circuit added 2/07)

Electronic canary:  (electronic circuit added 2/07)

Electronic siren 2:  (diagram added 2/07)

Equalizer Fuzz:  (schematic added 10/06)

Esp Sim Sound Impairment Monitor):  a method of determining just how much your amplifier modifies the original signal (added 4/02)

Fast Audio Peak Limiter:  (schematic / circuit design added 9/02)

FET audio mixer:  (electronic circuit added 2/07)

Fuzz-Box:  All-FET design.  Valve-like distortion behavior (added 3/05)

Guitar Effect Circuit  (aaroncake):  Wah, Fuzz and sustain  (added 4/02)

Guitar Effect Circuit (ee.washington.edu):  (electronic schematic / circuit added 4/02)

Guitar Reverb Circuit:  (electronic circuit added 4/05)

Guitar Reverb Effect Version 2:  (diagram added 2/07)

Guitar Reverb Pedal:  (schematic / circuit design added 9/02)

Guitar Tremolo Unit:  (circuit added 7/02)

Guitar Vibrato Unit:  (schematic / circuit design added 9/02)