Build A Simple Twin Tee Phase Shift Audio Oscillator and Audio Amplifier

  
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Above is a schematic diagram of a type of audio oscillator known as a twin `T` phase shift oscillator. It gets its name from the phase shift network made up of R3, R4 and C3 plus C1, C2 and R2 which shifts the phase of the signal fed back from the collector to the base by 180 degrees for the feedback to make the oscillator oscillate. You will noti
Build A Simple Twin Tee Phase Shift Audio Oscillator and Audio Amplifier - schematic

ce that the emitter of Q1 is not connected. Bringing this connection to ground will turn on the oscillator or "key it" as it`s called. You could connect this to a telegraph key and make a code practice oscillator. Now we need to be able to connect a speaker to it so we can hear the tone. To do this we need an audio amplifier, this is in order to have enough power from the oscillator to drive a small speaker. This part of the project uses an intergrated circuit or `IC` as the active component. IC`s contain many parts such as transistors, diodes and resistors all inside a very small package. This IC is designed to be an small low power audio amplifier and is not too easily damaged. Build these circuits one at a time or put them all on the same board. If you build them separately be sure to keep the connecting cables as short as possible. On the right is a diagram of the LM386 IC. Use this to find the correct pins to solder to. Actually, it`s best to use an IC socket and not to solder directly to the pins of the IC. Also make sure that all the grounds are tied together on all the boards if you do it in pieces. Government Surplus Auctions are an amazing source of cheap parts and good equipment! You might even find a car or a boat you always wanted for next to nothing! Get their list of auctions for your area. This is a little off the subject, but if you have ever heard of Nikola Tesla you might know about his involvement with...



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