Single Chip Theremin Circuit

 This schematic diagram show a single chip Theremin circuit.  Theremin is an electronic music instrument which sense hand movement to control the tones/frequency. This Theremin circuit uses two separate Colpitts LC oscillators to produce a beat frequency. The frequencies of  two Colpitts LC oscillators are mixed and then rectified.

Tremolo Effect Circuit for Electric Guitar

 

Tremolo circuit is a kind of sound effect. We can see this type of effect is applied  in guitar effect pedals.  Tremolo effect is produced if we modulate the amplitude of an audio signal. The shape of modulating signal can vary from square wave, sawtooth wave, or sine wave. When we use a square wave, then the effect produce a knocking-like sound which might be perceived like a percussive instrument.

Compact 3W BTL Audio Power Amplifier Schematic TDA7056

 Bridge-tied-load (BTL) configuration in an amplifier is basically a H-network  with the loud-speaker as the “bridge” between two active valve or switcher. This configuration allow a full alternating current signal to be produced at the load (loudspeaker) without a transformer or a symmetric power supply. Here are some benefits of BTL configuration:

Audible Logic Probe/Indicator Circuit

Logic indicator circuit / logic probe is used to identify logic level at any point of logic circuitry. The indicator can be visual (using LED, LCD, of 7 Segments) or auditory (using beeper or speaker). This circuit has a audible indicator, with the help of  a loudspeaker to produce indication tone.  Using the opamp,U1, as schmitt trigger, the Audio oscillator Q3-Q1-Q2 is isolated from TTL. Beside that, the op amp also acts as high input impedance inverter. The R8-R9 is used to set reference level at +16.6V which is a midway between low and high logic level. The Q3-Q2 will generate tone that indicate a high logic when the probe voltage is above +1.6V. If the probe voltage is below +1.6V then the  OP-amp output will saturate the Q1 and disables Q3-Q2 to cut off tone. Here is the schematic diagram of the circuit:

Tips for Increasing Bass Sound for Car System Sounds

To improve the quality of the car's sound system is to replace standard audio devices. The speaker is the audio device that is most often replaced, the reason for the user is because the sound quality standard speakers are not maximal. In addition to the poor sound quality, if the music volume is loud the speaker sound is not strong enough. 

Let's look at this article how the Power Amplifier & Subwoofer makes the power more maximal The second reason is because replacing speakers is more practical and installation is faster. The market can easily be bought at a fairly affordable price. But do not just buy speakers if you do not understand the specifications of the speaker, not even better, the results of the sound that is not in line with expectations. 

Car Audio Power Bridging Terms

Not only getting married is there a condition, bridging also has conditions. Because if you do not comply with these conditions then your power can be broken down in just a few hours or just a few songs with no maximum. Then what are the conditions? These conditions have been written by the manufacturer, so you should read the manual that indicates the condition if the power is in the cartridge. 

Then what are the conditions? These conditions have been written by the manufacturer, so you should read the manual that indicates the condition if the power is in the cartridge. In refilling the car audio power, we should not arbitrarily connect the cable, it must be right between the pluses and minuses - that's the first condition.

Bridging Car Audio Power

The method used in creating bridge audio power in a car.

a. stereo 2 channel bridge into 1 mono channel.The first method of car power audio bridging is combining 2 channel stereo output into 1 mono output to push 1 subwoofer speaker - this is called mono bridging. This means that under normal conditions a 2 channel power is for 2 4Ω speakers. Now, after a mono power cartridge is only to push a speaker, with impedance 2Ω; this of course the power of (rms) power will double. 

Note that the fewer speaker barriers, the power amp rms will increase as well; but with a note that this is also supported by the power amplifier. For example: A 2 channel stereo power amplifier has an output specification of 2x100watt @ 4Ω, bridge mode 1x400w @ 2Ω. This means that if the power is mono cartridge, we can use double coil speakers set to 2Ω, with output power to the speaker by 400 watts. Do you have to play at 2Ω only? The answer depends on the power, if you have stability playing at 1Ω or 4Ω there will certainly be no problem. 

Binaural Synthesizer/Mono to Stereo Converter Small Speaker/Phones Circuit

This is simple circuit can be used to drive two high-impedance loudspeakers or stereo phones, taking monophonic input (one channel), to produce a stereo signal which spread along the midway between loudspeakers when the input signal contain many frequency components. This is the figure of the circuit;

This circuit has two channels, left and right, right channel has high-pass active filter and left channel has low-pass active filter with cut off 750Hz. This circuit is designed for low to high-impedance speaker or phones. In the schematic diagram below, you can see the output is passed through a series resistor. Without this resistor, uncontrolled oscillation might occur on the output channel when low impedance 8-ohm loudspeakers or phones are connected to the outputs directly. Op amps will drive 8-ohm loads with low volume levels, but give ample volume with 2000-ohm phones, so the higher the impedance the higher the power.

Audio Monitoring Circuit

This is a design schematic of audio monitoring system which the transmitter will pickup sound from one location and the receiver at other location will reproduce it. The receiver and transmitter of the circuit is connected by one set of wire. And in here the power supply and transmitted signal is share in the same wire. This is a figure for a complete design schematic.


The operation of the circuit is the audio signals picked up by the microphone will be amplified by the double stage amplifier build around transistors Q1 and Q2.The POT R2 controls gain of the amplifier. The power supply for this circuit is drawn from the interconnection lines itself. The capacitor C4 bypasses all audio frequencies & noise from the line and ensures pure DC for the circuit. The output of the amplifier (audio signal) is coupled to the line via the capacitor C6. At the receiver end the capacitor C7 extracts the audio signal from the line and feds it to the inverting input of IC1 (TL071) which is wired as a voltage amplifier. Output of IC1 is given to the input of IC2 (LM386) which is a integrated power amplifier.IC2 provided necessary current gain to drive the speaker. The POT R14 can be used control the gain of receiver. Capacitor C11 isolates audio frequencies and noise from the power supply of both the ICs.

Dual Input Far Field Noise Suppression Microphone Amplifier Circuit

This is a circuit diagram for microphone amplifier. This circuit is using LMV1090 as based op amp signal in the circuit. This is the figure of the circuit;

The LMV1090 is a fully analog dual differential input, differential output, microphone array amplifier designed to reduce background acoustic noise, while delivering superb speech clarity in voice communication applications. The LMV1090 preserves near-field voice signals within 4cm of the microphones while rejecting far-field acoustic noise greater than 50cm from the microphones. Up to 20dB of far-field rejection is possible in a properly configured and using ±0.5dB matched microphones. [Schematic circuit source: National Semiconductor Notes].

Dual Channel Digital Volume Control Circuit

This circuit is design for control the volume audio. This circuit for replacing your manual volume control in a stereo amplifier. This circuit is control by three IC, there are 555 timer, 74LS193, and 4066. This is the figure of the circuit.

IC1 timer 555 is configured as an astable flip-flop to provide low-frequency pulses to up/down clock input pins of pre-stable up/down counter 74LS193 (IC2) via push-to-on switches S1 and S2. To vary the pulse width of pulses from IC1, one may replace timing resistor R1 with a variable resistor. Operation of switch S1 (up) causes the binary output to increment while operation of S2 (down) causes the binary output to decrement. The maximum count being 15 (all outputs logic 1) and minimum count being 0 (all outputs logic 0), it results in maximum and minimum volume respectively.

Computer Microphone Circuit

This circuit was submitted and design by Lazar Pancic from Yugoslavia. The sound card for a PC generally has a microphone input, speaker output and sometimes line inputs and outputs. The mic input is designed for dynamic microphones only in impedance range of 200 to 600 ohms. Lazar has adapted the sound card to use a common electret microphone using this circuit. He has made a composite amplifier using two transistors. This is the figure of the circuit.

This is the explanation about the principle work of the circuit. The BC413B operates in common emitter to give a slight boost to the mic signal. This is followed by an emitter follower stage using the BC547C. This is necessary as the mic and circuit and battery will be some distance from the sound card, the low output impedance of the circuit and screened cable ensuring a clean signal with minimum noise pickup.

Automatic Loudness Control Circuit

This is a simple design for automatic loudness control in audio. A simple approach to this problem can be done inserting a circuit in the preamplifier stage, capable of varying automatically the frequency response of the entire audio chain in respect to the position of the control knob, in order to keep ideal listening conditions under different listening levels. This is a figure of the circuit.


The circuit is shown with SW1 in the "Control-flat" position, i.e. without the Automatic Loudness Control. In this position the circuit acts as a linear preamplifier stage, with the voltage gain set by means of Trimmer R7. Switching SW1 in the opposite position the circuit becomes an Automatic Loudness Control and its frequency response varies in respect to the position of the control knob by the amount shown in the table below. C1 boosts the low frequencies and C4 boosts the higher ones. Maximum boost at low frequencies is limited by R2; R5 do the same at high frequencies.

This is a list component that must using for built the circuit.
P1 10K Linear Potentiometer (Dual-gang for stereo)

R1, R6, R8 100K 1/4W Resistors
R2 27K 1/4W Resistor
R3, R5 1K 1/4W Resistors
R4 1M 1/4W Resistor
R7 20K 1/2W Trimmer Cermet

C1 100nF/63V
C2 47nF/63V
C3 470nF/63V
C4 15nF/63V
C5, C9 1µF/63V
C6, C8 47µF/63V
C7 100pF/63V

IC1 TL072 Dual BIFET Op Amp

SW1 DPDT Switch (four poles for stereo)

Intelligent Trailing Switch Circuit

This is a design effective circuit in which the equipments connected at the so called trailing sockets will run only if the equipment connected at the control socket is switched on. For example, let’s connect a motor is connected to the control socket and a lamp is connected at the trailing socket. The lamp will glow only when the motor is running. This is the figure of the circuit.


Explanation of the operation circuit is when the load connected at the control circuit is switched on, the load current flows through the diodes and as a result there will a voltage drop across the diodes. This voltage drop is sufficient enough to switch on the sensitive triac T1 and the equipments connected at the trailing sockets gets power supply. The components R2 and C1 forms a snubber circuit which protects the triac from transient fluctuations. The triac T1 must be a 600V, 8A, high sensitive gate type like TIC 225M. Fit the triac with a heat sink. The maximum load that can be connected at the trailing socket is 1000W. Take at most care while handling this circuit as it is connected to 230V AC.

Almost all equipments like motors, drills, blenders, fan, old TV, radio, amplifiers etc can be connected at the control socket. In case of modern TV, computers, amplifiers, etc the power switch does not completely isolate the equipment and the equipment will draw a small amount of current in the standby mode which is sufficient enough to trigger the triac. Such equipments cannot be used on the control socket because it makes the trailing equipments ON even if the control equipment is OFF.

Audio Clipping Indicator Circuit

This is a design circuit can be used to identify whether there is a clipping in a particular wave form. Clipping is a phenomenon in which the amplitude of a particular waveform drops before it reaches the expected limit. This circuit glows an LED as an indication if the signal under test has clipping. The circuit is very useful in sorting out distortion problems in amplifiers. This is a figure of the schematic.


The circuit is based on a window comparator based on the two op amps inside the IC1 (TL082). Operation this circuit is based on the circuit detects the positive or negative peak value reached by the input signal. The output of the op amp is combined by the two diodes D1 & D2 and drives the transistor Q1 to glow the LED.

The capacitor C5 is employed to induce a small time delay in order to detect very fast and short peaks. The POT R1 can be used to set the level of clipping at which the LED has to glow. The circuit can be used with almost all sorts of mixers, power amplifiers and preamplifiers. The circuit can be powered from a 9V PP3 battery. The POT R5 can be use to calibrate the circuit.

Audio Remote Security and Monitor

This is a audio security monitor circuit. This circuit is built by two IC, LM386 and TL071. This design is a simple design that can use this in the garden and listen for any unusual sounds, or maybe just wildlife noises. If you have a car parked in a remote location, the microphone will also pick up any sounds activity in this area. The cable may be visible or hidden, screened cable is not necessary and you can use bell wire or speaker cable if desired. In this figure is show a circuit and how the circuit done.

The work of this circuit is starting the power supply. This circuit used 12V as a standard power supply voltage, or a 12V car battery may be used. The circuit is in two halves, a remote microphone preamp, and an audio amplifier based around the National Semiconductor LM386 audio amplifier. The remote preamp uses an ECM microphone to monitor sound. A direct coupled 2 stage amplifier built around Q1 and Q2 amplify the weak microphone signal. Preset resistor R2 acts as a gain control, and C1 provides some high frequency roll off to the overall audio response. Q1 is run at a low collector current for a high signal to noise ratio, whilst Q2 collector is biased to around half the supply voltage for maximum dynamic range. The power supply for this preamp is fed via R10 and R6 from the 12V supply. C4 ensures that the preamp power supply is decoupled and no ac voltages are present on the power lines. The amplified audio output from Q2 collector is fed into the supply lines via C6 a 220uF capacitor. The output impedance of Q2 is low, hence the relatively high value of C6. C6 also has a second purpose of letting the output audio signals pass, whilst blocking the dc voltage of the power supply.

At the opposite end, C7 a 10uF capacitor, brings home the amplified audio to the listening location. The signal is first further amplifier by a x10 voltage gain amplified using the TL071. C8, a 22pF capacitor again rolls off some high frequency response above 100kHz. This is necessary as long wires may pick up a little radio interference. After amplification by the op-amp, the audio is finally passed to the LM386 audio amplifier. R14 acts as volume control. R13 and C12 prevent possible instability in the LM386 and are recommended by the manufacturer. Audio output is 1 watt into an 8 ohm loudspeaker.

Reduces noise and ripple circuit for audio band

The circuit in the figure is reduces noise and ripple circuit by at least 35 dB over the audio range of 100 Hz to 20 kHz. This reduces noise and ripple circuit provides a clean source of 5V power for driving audio circuits in portable applications such as cellular phones and multimedia notebook computers. Most linear regulators reject noise only to about 100 Hz, and the bulk of a low-frequency passive filter is unwelcome in portable applications. The figure is show below;


The principle work of the circuit accepts noisy VCC in the range of 4.5 to 6V and produces quiet VCC at a dc level 7% lower than the input. For example, the circuit produces 4.65V at 1A from a nominal 5V source, with only 200 µA of quiescent current. The layout is small; the circuit consists of one SOT-23 transistor, one shrink SO-8 op amp, and a few passive components. The largest capacitor is 10 µF, and the resistors can be 0.1W or surface-mount 0805. The circuit acts as a wide-bandwidth buffered voltage follower (not a regulator) with a dc output level that is 7% below that of VIN. R1 and R3 form a voltage divider that provides the 7% attenuations, and C1 helps to form a 93% filtered replica of VIN at the op amp’s inverting input. The op amp’s small input-bias current (typically 25 nA) allows large resistor values for R1 and R3, yet limits the maximum dc error to only 20 mV. The result is a low-pass filter with a 2-Hz corner frequency that provides 20 dB of attenuation at 20 Hz.

Because the op amp’s common-mode input range extends from rail to rail, its noninverting input can directly sample the output voltage. R2 and C2 filter the op amp’s supply voltage to provide the op amp with a lower output impedance and better power-supply rejection at high frequencies. This filter’s 300-Hz roll-off augments the op amp’s already high 110-dB PSRR.

Telephone Audio Interface Schematic

Audio from a telephone line can be obtained using a transformer and capacitor to isolate the line from external equipment. A non-polarized capacitor is placed in series with the transformer line connection to prevent DC current from flowing in the transformer winding which may prevent the line from returning to the on-hook state. The capacitor should have a voltage rating above the peak ring voltage of 90 volts plus the on-hook voltage of 48 volts, or 138 volts total. This was measured locally and may vary with location, a 400 volt or more rating is recommended. Audio level from the transformer is about 100 mV which can be connected to a high impedance amplifier or tape recorder input. The 3 transistor amplifier shown above can also be used. For overvoltage protection, two diodes are connected across the transformer secondary to limit the audio signal to 700 mV peak during the ringing signal. The diodes can be most any silicon type (1N400X / 1N4148 / 1N914 or other). The 620 ohm resistor serves to reduce loading of the line if the output is connected to very low impedance.