CIRCUIT || Stereo Headphone Amplifier

Here’s a top-class headphone amplifier that can drive high or low-impedance phones to full power levels, with very low noise and distortion. For best performance, it can be teamed with the Stereo Preamplifier described last month. Alternatively, it can be used as a standalone unit, requiring only a power supply and a volume control potentiometer for use with any line-level signal source (CD/MP3 player). It even includes dual outputs, so you can listen with a friend!

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CIRCUIT || 7 MHz CW/AM QRP TRANSMITTERS

The circuit of a 7MHz C W / A M QRP transmitter described here can be used to transmit either CW or audio frequency modulated signal over a 7MHz carrier.

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CIRCUIT || 2-LINE INTERCOMCUM- TELEPHONE LINE CHANGEOVER CIRCUIT

2-LINE INTERCOMCUM- TELEPHONE LINE CHANGEOVER CIRCUIT

The circuit presented here can be used for connecting two telephones in parallel and also as a 2-line intercom. Usually a single telephone is connected to a telephone line. If another telephone is required at some distance, a parallel line is taken for connecting the other telephone. In this simple parallel line operation, the main problem is loss of privacy besides interference from the other phone. This problem is obviated in the circuit presented here. Under normal condition, two telephones (telephone 1 and 2) can be used as intercom while telephone 3 is connected to the lines from exchange.

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