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This is very very simple circuit audio amplifier  based on IC7057T  , you just use 3 components you can make this circuit . And the minimum voltage is 1 Volts , with just 1 Volt  you can operate this amplifier. Maximum voltage 6,5 volts . Maximum Power output 35mW with 32 ohms impedance. See circuit below : Very simple stereo amplifier

The schematic above is amplifier based on ic TA7211P or TA7212P , circuit above using OT transformer as a booster amplifier again. The amplifier suitable used on outside / field, because by using a transformer OT is identical to the PA amplifier. Part List : R  = 1K , 10R , 3K3 C  = 1uF , 10uF , 1n , 68u, 3u3, 2n2 x 2, 100u  IC = TA 7211P / TA7212P Technical information : Max Vcc = 15 VDC Min Vcc  = 4 VDC Po            = 3,4 W Rl            = 8 Ohm Icco         = 16 mA

   4 Transistor FM Transmitter Circuit Diagram Build a  4 Transistor FM Transmitter Circuit Diagram. This 4 Transistor FM Transmitter Circuit Diagram provides an FM modulated signal with an output power of around 500mW. The input microphone pre-amp is built around a couple of 2N3904 transistors (Q1/Q2), and audio gain is limited by the 5k preset trim potentiometer.  The oscillator is a colpitt stage, frequency of oscillation governed by the tank circuit made from two 5pF ceramic capacitors and the L2 inductor. The output stage operates as a 'Class D' amplifier, no direct bias is applied but the RF signal developed across the 3.9uH inductor is sufficient to drive this stage. The emitter resistor and 1k base resistor prevent instability and thermal runaway in this stage.

The MS6714 is a 4 stereo inputs/2-channel outputs digital control Audio Processor for the low voltage operation. Volume, Tone (bass and treble), and balance (left/right) processor are incorporated into a single chip. The MS6714 also has the loudness function and selectable input gain. These functions CAN be built a Hi-Fi Audio system easily. All 2 visit page. functions are programmable via the serial I C bus. The default states of the chip as the power is on are: the volume is -78. 75dB, the stereo 4 is selected, all the speakers are mute and the gains of the input stage, the bass and the treble are 0dB. By MOSA electronics corp. Stereo Inputs And 4-Channel Outputs Volume Tone Balance 

24v DC is a very popular voltage used in industrial settings. This hobby circuit below was designed to accept four different 24v DC alarm input signals, which are then used to drive a single low power beeper. The beeper is a magnetic type with its own oscillator/driver. The four diodes form an “OR” gate so any one of the four inputs will cause the beeper to make noise. A CMOS version of the popular 555 timer is used to strobe the beeper on and off at about 1Hz.   Copyright: Discover Circuits

The September 5 event by Nokia and Microsoft could mark the launch of the first Windows Phone 8 devices. It could be the Nokia Lumia 920, which is rumored to pack some of the best hardware till date on a Windows Phone. Now, The Verge is reporting that this new Lumia device could sport wireless charging, 32GB internal storage and an 8-megapixel PureView camera. The Nokia Lumia 920 [ pictured in yellow ] wireless charging support (Qi wireless power standard) could be provided via an inductive method — lining the device up to the contacts on a charging pad. Apart from this, the Lumia 920 is rumored to sport a 4.5-inch HD screen, a dual-core processor, 1GB RAM, an 8-megapixel camera, and 32GB internal storage. The 8-megapixel camera on the Lumia 920 could still be marketed as the PureView camera, even without the 41-megapixel camera. Yet another Nokia Lumia 820  [ pictured in red ]could make its debut alongside the Nokia Lumia 920. According to the latest leaks from EvLeaks (via Twi...

Testing was done in part 3, this last part is consist of following: Final assembly The front panel assembly can now be  lowered down onto the case. Make  sure that the three ribbon cables are  folded neatly into the space above the  lower PCB and not caught between the  edges of the case or lid.  Fasten the case together with four  M4 screws into the corner holes, then  fit the knobs to the rotary switch and  the pot and the assembly is complete.  Testing the HV crowbar It’s now necessary to check that the HV crowbar circuit is working correctly. To do this, power up the unit, wait a few seconds and then press the Menu Select button. You will get a display like this: Device to Test:▲ 1:Diode/Zener▼ Press Enter and then the Up button. The display will then show: Test parameter:▲ Irev(OPV)▼ Press Enter again. Set the Device Operating Voltage to 25V, using the right-hand knob. Then press the Test On/Off button to start the test. Now careful...

The HA13155 is four-channel BTL amplifier IC designed for car audio, featuring high output and low distortion, and applicable to digital audio equipment. It provides 33 W output per channel, with a 13.7 V power supply and at Max distortion. Circuit diagram: Datasheet for HA13155: Download

Opto-Isolated 4-Channel Triac Board (R) is used for fast switching applications. Ideal for switching mains circuits, lights, appliances and small load. Each circuit is effectively isolated with opto-isolators on each channel, TTL inputs control each channel. Trigger input 2-12 VDC Mains supply input 230 VAC or 110 VAC Output 1 A @ 230 VAC (RMS ON STATE CURREN 4 AMPS EACH CHANNEL) Snubber circuit for inductive load Jumper for common cathode ground Box Header connector for connection of control signal Screw terminal connector for Load Four mounting holes of 3.2 mm each PCB dimensions 139 mm x 73 mm [ ]