Audio Fader
In this circuit, Ql is a simple amplifier that has its gain controlled by a variable emitter resistance supplied by FET Q2. In ...
Audio-Frequency Doubler
Often the frequency of a signal must be doubled: modulator/demodulator chip LM1496 is an ideal basis for this. From...
Allophone-generator
The circuit, a general-purpose system with many uses, vocalizes 59 allophones contained in the speech processor. After filtering and amplification, its pulse-c...
Tremolo
This simple circuit can color the sound coming from your audio system. Clocking for the circuit is provided by an oscillator built from one quarter of a 4093...
Electronic-tremolo
The tremolo effect is generated by a repeating volume change at a rate usually between 1 and 15Hz. The timer produces a low frequency square wave that is smoot...
Magnetic-phono-preamplifier
This simple stereo amplifier uses a National LM3871C. The pin numbers in parentheses are for one channel, and those not in parentheses are for the other chan...
Equalized-preamp-for-magnetic-phonograph-cartridges
This circuit uses a CA3130 BiMOS op amp. Amplifier is equalized to RIAA playback frequencyresponse specifications. ...
Rumble-scratch-filter
This is a variable bandpass amplifier with adjustable ...
Wien-bridge-filter
Most audio tone controls affect midband gain, and !bey often create booming or hissing sounds when activated. You can avoid tbese problems by using a dual Wien...
Ten-band-octave-equalizer
A series of active rffilters using National LM3481C comprises a ten-band graphic equalizer. Cl, C2, Rl, and R2 ...
Ic-preamplifier-tone-control
The circuit is a form of the so-called ""Americanized" version of the Baxandall negative-feedback tone control. At very low frequencies, the reactance of the c...
Telephone-amplifier
Audio from the telephone is inductively coupled to the base of Ql. which is used as a preamp. The preamp provides a gain of about 75 dB, to boost the input sig...
Speakerphone
This circuit consists of two audio channels, a control circuit, and a hybrid irlterface circuit. The gain of each audio channel is con· trolled by the contr...
Sound-activated-switch
A sensitive electret microphone picks up the sound and feeds the signal to a two-stage amplifier circuit, consisting of Ula and Ulb. The amplified output of ...
Voice-operated-switch
The sound picked up by SPKRl, which acts as a microphone, is fed to transistor amplifier Ql. The output of Ql is applied across coupling transformer T1 and i...
Sound-activated-switch
Al and A2 are two sections of a quad comparator. The first, Al, functions as an amplifier and detector. Resistors R~and R6 set the gain at 100; the output of A...
Race-car-motor-crash
For two simultaneous race-car sounds. ...
Chug-chug
A CA3240 dual MOSFET-input device is used as a white-noise source. Op amp IC2 is used as a driver stage for the push-pull output stage formed by Q5 and Q6. Tra...
Fuzz-box
The 741"s maximum gain of 20,000 is pushed to nearly 3 million dB, and therefore distorts the output. That distortion provides the fuzz sound. ...
Sound-effects-generator
A variable dock-pulse generator is made up of two sections of IC1 (a 4069 CMOS hex inverter). Rl, Sl, and capacitors Cl through C6. By adjusting Rl and switchi...