Low cost Mic Mixer

Description This is the schematics of a low cost mic mixer that can be assembled from the components in your junk box.This two channel mike mixer is designed for handling high impedance dynamic microphones.Transistor Q1 can be any general purpose pnp transistor like BC177 or BC157B. Resistor R5 biases the transistor while R3 and R4 provides channel isolation. How ever better the transistor quality better the performance.  C1 and C2 performs the job of input coupling and DC isolation while C4 is the output DC decoupling capacitor.Resistors R1 and R2 can be used for the level control of input signals….

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USB sound card

Description. Designing and building a USB sound card is no longer a head ache because we have got the PCM 2702 integrated circuit from Texas Instruments. The PCM2702 is an integrated 16 bit digital to analog converter that has two digital to analog output channels. The integrated interface controller of PCM2702 is compliant to the USB 1.0 standards. The IC can handle sampling rates of 48 KHz, 44.1 KHz and 32 KHz. The IC also has a number of useful features like on-chip clock generator, digital attenuator, play back flag, suspend flag, zero flag, mute function etc. The most interesting…

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40W amplifier using TDA1514

Description. Many electronic circuits dealing with audio amplifier circuits have been published here. This is just another one and here we use the TDA 1514 high performance hi-fi amplifier from Philips. The IC has a bunch of useful features like thermal protection, mute-standby facility, low harmonic distortion etc. The amplifier operates from a dual +25/-25 V DC power supply and can deliver 40Watts output power to an 8 ohm speaker. The audio signal to be amplified is fed to pin 1 of the IC and the capacitor C2 acts as a DC de-coupler. The resistors R3 and R4 determine the…

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3 way active cross- over network

Description. Here is the schematic of a 3 way active cross- over network circuit that finds a lot of application in audio amplifier systems. The heart of this circuit is National Semiconductor’s IC LF353 which is a dual JFET input operational amplifier with internally compensated input offset voltage. The IC LF353 has high bandwidth, low offset currents, and low input bias current due to the JFET based input stage. The working of the circuit is very simple and straight forward. Two LF353 ICs are used here. The input audio signal is first buffered using the opamp IC2a and POT R7…

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2 x 32 Watts stereo amplifier

Description. The circuit given here is of a 2 x 32 Watt stereo amplifier using the famous TDA2050V IC from ST Microelectronics. The TDA2050V is an integrated monolithic 32 watt class AB audio amplifier IC available in the Pentawatt package. The IC has lot of good features like low distortion, short circuit protection, thermal shut down etc. Two TDA2050V ICs are used here, one for each channel. For each channel the input audio signal is fed to the non-inverting input of the IC through 1uF (Non-Polarized electrolytic) capacitor and this capacitor performs the job of DC decoupling. The ratio of…

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4 X 15 Watt power amplifier

Description. A lot of electronic circuits in the domain of audio amplifiers are already been published here. This circuit is a little different because it is a four channel amplifier. Each channel of this amplifier can deliver an output of 15Watts into a 4 ohm speaker. The amplifier can be operated from a single 12V DC supply and this makes it possible to use this amplifier in car audio applications too. The circuit is based on the 15W BTL X 2 channel audio power amplifier IC TA8215 from Toshiba. Even though chip is specifically designed for car audio applications it…

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How to make a Rheostat

I have already explained in detail the working of a rheostat. To know more about the component click on the link below. TAKE A LOOK : POTENTIOMETER AND RHEOSTAT – WORKING AND COMPARISON Although the below explained process is not applicable for any electronic circuits, you will clearly get a clear idea on how a rheostat works. Components The components needed for the connection are Flashlight bulb and socket [1] Dry cell lantern battery/D-cell battery [2] Wire [About 15 to 17 inches and another one 2 inches] Spring [1] Wire Clippers [A pair] A typical spring can be obtained from…

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Automatic cooler fan for amplifiers

Description. The schematic of an automatic cooler fan for audio amplifiers is given here. The circuit automatically switch ON the cooler fan whenever the temperature of the heat sink exceeds a preset level. This circuit will save a lot of energy because the cooler fan will be OFF when the amplifier is running on low volume. At low volume less heat will be dissipated and it will not trigger the cooler fan ON. The temperature is sensed using an NTC (negative temperature coefficient) thermistor R2. Junction of thermistor r2 and resistor R1 is connected to the inverting input (pin3) of…

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Police siren using NE555

Description. A lot of electronic circuits using NE555 timer IC are already published here and this is just another one.Here is the circuit diagram of a police siren based on NE55 timer IC. The circuit uses two NE555 timers ICs and each of them are wired as astable multivibrators.The circuit can be powered from anything between 6 to 15V DC and is fairly loud.By connecting an additional power amplifier at the output you can further increase the loudness. IC1 is wired as a slow astable multivibrator operating at around 20Hz @ 50% duty cycle and IC2 is wired as fast…

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Speaker protector

Description. When the amplifier is switched on, the speaker gets popped up by a high voltage and you can hear a loud thud sound from the speaker. This stuff is very harmful to the speaker and it drastically reduces the speaker’s life. The circuit shown here connects the speaker to the power amplifier output only after a few seconds the amplifier is powered ON. A simple transistor based time delay circuit is used for attaining the purpose. The circuit is so connected to the existing amplifier that, when the amplifier is powered on the bridge D1 also gets powered through…

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