Sound-Level Meter

The NE604"s signal-strength indicator section is used, based on an internal logarithmic converter. This enables a linear ...

Stereo Audio Power Meter

This circuit is used to meter the audio power output of an amplifier feeding a speaker. RY1 is actuated if excess ...

Sound-Level Meter

An electret microphone feeds an audio amplifier/rectifier combination. The amplifier has switchable gain. The rectifier o...

Balance Indicator

If your amplifier is fitted with two level controls, it actually offers you a balance control and a level control. A draw...

Audio Amplifier Volume Indicator

The indicator is intended for use with an audio amplifier or preamplifier, but it can also be used in othe...

White Noise Generator

Germanium transistor Ql is used as a noise generator in the audio range. Ul acts as a high-gain amplifier. Ql is not ...

Scratch Filter

Designed to produce 12-dB/octave roll-off above the 10-kHz cutoff frequency, this LP active filter will help reduce needle s...

Turntable Rumble Filter

Many record players unfortunately exhibit two undesired side effects: rumble (noise caused by the motor and the turntable) and other low-frequency spurious sig...

Audio Compressor/Audio-Band Splitter

This 2-band compressor splits the audio into high and low frequencies and allows independent adjustmen...

Preamplifier For Magnetic Phono Cartridges

This amplifier is intended to be added to preamplifiers that have no phono input. Such a phono i...

Receiver Audio Circuit

This simple receiver AF amplifier can supply several hundred milliwatts to an 8- speaker. The gain is about 200X. If...

Bull Horn

This bull horn uses U1 as a driver stage and U2 as an output driver. U1 is set up for a gain of 200. The microphone should have a...

Voice Scrambler/Disguiser Circuit

This circuit uses two balanced modulators to produce a DSB signal and then reinsert the carrier, except t...

Voice Scrambler/Descrambler

This circuit uses an NE602 as an inversion mixer. U2 is set to run at about 2.5 to 3.5 kHz. U3 drives a loudspe...

Derived Center-Channel Stereo System

A simple method of deriving a center or third channel without the use of an extra transformer or ampli...

Audio Ditherizing Circuit For Digital Audio Use

By adding a small amount of noise to a signal to be digitized (about 0.7 bit): where: n = #...

Musical Envelope Generator And Modulator

A gate voltage is applied to initiate the proceedings. When the gate voltage is in the ON state, Q...

Analog Delay Line (Echo And Reverb)

This circuit uses an SAD 512D (Reticon) chip, which is a 512-stage analog shift register. By varying th...

Vocal Eliminator

Otherwise properly mixed sounds often suffer from a predominant solo voice (which might, of course, be the intention). If ...

Audio Equalizer

Designed for communications use, this equalizer circuit uses a Mitsubishi M5226P audio equalizer IC to adjust frequency res...