Audio Filters

Quick view of Amplifier Compressor MC3340P

This audio compressor circuit use a MC3340P as a variable gain amplifier. The output is rectified and TR2 controls the gain of the ICL ..

Automatic audio fader circuit

Automatic audio fader circuit

The automatic fader drops at the background music while the narration is in place. The control input through RIO, a preset audio level control, into an emitter-follower buffer stage CQI). The buffer provides high input impedance and ensures that the source impedance is low enough to drive the rectifier and smoothing circuit, consisting of DI, D2, and C5. The smoothed output drives a simple LED circuit. LD and R8 form an IR input pad through which the output is fed through C6 and C7 to the output jack. ..

Active crossover circuit with TL074

Active crossover circuit with TL074

An audio source, like a mixer, preamp, EQ, or a recorder, is fed to the input of the Electronic Crossover Circuit. This signal is either AC or coupling, depending on the setting of switch 51, the non-inverting input of buffer amplifier Ul-a, a section of a quad BIFET, low amp TL074 noise made by Texas Instruments op. This stage has a gain of 2, and its output is distributed to both a low pass filter made by R4, R5, C2, C3, and Uld op-amp, and a high-pass filter made by R6, R7, C4 , C5, and op amp ULC. These are12 dB / octave Butterworth filters. The response of the Butterworth filter was chosen because it gives the best compromise between the damping and phase. ..

Automatic level control with NE570

Automatic level control with NE570

The NE570 can be used to make a high performance compressor FTA, except that the rectifier is connected to the input. This makes gain inversely proportional to the input level so that a drop of 20 dB input level will produce an increase of 20 dB gain. The output remains at a constant level. As shown, the circuit will maintain an output level of ± 1 dB for an input range of + 14 to -43 dB at 1 kHz. ..

Q-multiplier filter circuit

Q-multiplier filter circuit

This circuit is selective for the tuning adjustment between two closely spaced tones audio. The frequency is dependent on the selective value capacitors and resistors in the feedback circuit between the collector and base of Q1. With the values shown, the frequency can be "tuned" to a hundred cycles or so-around 650 Hz Ri and R2 should be grouped. R3 potentiometer transmitter determines the sharpness of the response curve. ..

Overload speaker protection circuit

Overload speaker protection circuit

The circuit input is taken from the terminal loudspeaker or amplifier output jacks. If the right channel is large enough to charge C1 to a potential which exceeds the breakdown voltage of the emitter of Ql, a voltage pulse appears in R7. Similarly, if the left channel signal is large enough to charge C2 to a voltage that is greater than the breakdown voltage of the emitter of Q2 ", a pulse appears in R7. The pulse triggers in R7 5CRI. A door sensitive SCR (LGT less than 15 RNA or IGT is the gate-trigger current) that locks in a conducting state and energizes Ryl. The action of the relay will interrupt the speaker circuit. and silence follows you must alert on the problem. ..

Audio compressor circuit

Audio compressor circuit

The amplifier drives the base of a common emitter PNP MPS6517 operating with a voltage gain of about 20. RL control varies the quiescent point of the transistor Q, so that varying amounts of signal exceed the level of V r, diode D 1 rectifies the positive peaks Ql output is only when these peaks are more larger than r V "'" 7. 0 volts. The result is filtered ex Rx. s, controls the charging time constant or time of attack. Cx is involved in two loading and unloading. R2 (150 K, the input resistance of the emitter-follower Q2) controls the decay time. ..

FSK Demodulator/Tone Decoder with RC2211N

FSK Demodulator/Tone Decoder with RC2211N

A monolithic phase locked loop for data communications. The IC contains a basic phase locked loop for tracking an input signal within the pass band, a quadrature phase detector which provided carrier detector and an FSK voltage comparator which provides FSK demodulation. In the circuit shown, the IC is used as an FSK demodulator such as would be found in the receiver circuit of a modem...

Feedback Band-Pass Filter

Feedback Band-Pass Filter

One application of this handy circuit is a graphic equalizer, created by feeding a signal to a number of parallel band-pass filters each tuned to a different frequency; typically octaves apart. Then, you can adjust the strength in each band via a front panel potentiometer. The outputs of all the filters are then summed to create overall frequency response of the equalizer...

Bandpass Filter schematic

Bandpass Filter schematic

A bandpass filter passes a range of frequencies while rejecting frequencies outside the upper and lower limits of the passband. The range of frequencies to be passed is called the passband and extends from a point below the center frequency to a point above the center frequency where the output voltage falls about 70% of the output voltage at the center frequency. These two points are not equally spaced above and below the center frequency but will look equally spaced if plotted on a log graph. The percentage change from the lower point to the center will be the same as from the center to the upper, but not the absolute amount...

Opamp Filters schematics

Opamp Filters schematics

The figures below illustrate using opamps as active 2nd order filters. Three 2nd order filters are shown, low pass, high pass, and bandpass. Each of these filters will attenuate frequencies outside their passband at a rate of 12dB per octave or 1/4 the voltage amplitude for each octave of frequency increase or decrease outside the passband. ..

Tone Control circuits

Tone Control circuits

There are two types of tone control circuits, passive and active. The passive kind consist of the pots, resistors and capacitors. There is an amplifier tube before the tone circuit and another tube amplifier after the tone circuit but there are no tubes directly involved in the tone control circuit itself. In the active kind there are amplifying devices involved in the tone control circuit. A circuit which looks the same as a passive circuit is placed in the feedback loop of an amplifier stage. This kind of circuit is common place in semiconductor based amplifiers because the amplifying devices take up little space and power. ..

Two way Loudspeaker cross-over

Two way Loudspeaker cross-over

The resistance of loudspeakers is characterized in a frequency depending on the destination and their press. Loudspeakers are distinguished, as for the destination, in loudspeakers of low frequencies, woofer intermediate, mid-range and high tweeter. Their resistance in W is 4W, 8W and 16W. Cross-over that we present it is intended for loudspeakers 8W. The loudspeakers are distinguished by various characteristics that him make distinguish between them. That characteristics that us interest for the manufacture that we make, are their complex or more simply resistance and diagram that us gives the relation of attribution of sound as for frequency (sensitivity)...

Low pass filter for Subwoofers

Low pass filter for Subwoofers

In the form it appears the theoretical circuit of filter. In first glance we see three different circuits that are mainly manufactured round two operational amplifiers. This circuits constitute mixed, amplifier with variable aid and a variable filter. The manufacture end needs a circuit of catering with operational tendency of catering equal with ±12. the operational amplifiers that constitute the active elements for this circuits of are double operational type as the TL082 and NE5532. The operational these amplifiers belong in a family provided with transistor of effect of field IFET in their entries. Each member of family allocates in their circuit bipolar transistor and effect of field. This circuits can function in his high tendency, because that they use transistor of high tendency...

Subsonic audio Filter

Subsonic audio Filter

The circuit shown is completely conventional. The Q of the filters has been optimised to allow a higher input impedance than would otherwise be possible, with the final Q of the two filters being almost exactly 0.707 (i.e. a traditional Butterworth filter). Although in theory the tolerance of both resistors and capacitors should be 1% or better, in reality it is not that important. 1% metal film resistors are recommended (as always) but only for lowest noise, and capacitors are standard (i.e. 5% or 10%) tolerance. Yes, this will cause the response to deviate from that shown below (see Figure 2), but compared to other errors in the system (recording EQ, room LF node problems, etc.) these may be considered minor. ..

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