Karaoke amplifier mixes and amplifies both inputs and give out put to a load or speaker. The circuit under discussion consists of an amplifier with 6 band Graphic equalizer. It consists of power supply, mixer / pre amplifier, graphic equalizer and power amplifier stages. The circuit will include following essential elements
1. Two inputs, 1 for microphone and a second for Line input, which could be mixed and boosted with a common emitter amplifier stage.
2. A six-band graphic equalizers stage.
3. A common emitter voltage boost amplifier stage.
4. A common collector power amplifier.
5. Circuit works from mains power supply.
Detailed circuit operation is given as under:-
The power supply is connected to pre amplifier and power amplifier blocks. The Transformer T1 is a simple step-down transformer which takes 240 V Ac current and gives out 9.5 V Ac at current rating of 1.3 amps approximately. The circuit requires steady DC current therefore output of transformer is applied to rectifiers. Transformer works on the principle of mutual induction of two coils. When current in the primary coil is changed, the flux linked to the secondary coil also changes. Consequently, an EMF is induced in the secondary coil. The transformer T1 consists of a rectangular core of soft iron in the form of sheets insulated from one another. Two separate coils of insulated wires, a primary coil and a secondary coil are wound on the core. ...