15W Valve Modulator Amplifier circuit

Posted on May 3, 2017

The output of this modulator consists of two 6AQ5 lamps in a PUSH-PULL arrangement with a maximum output of 15W. 6C4 is used as a reversing lamp. The pre-amplifier role is played by the double-stage ESC83. The potentiometer R1 performs voice volume adjusters and a crystalline microphone is connected to the amplifier input. The amplified frequency band extends from 50C / S to 10KC / S. At these extreme frequencies amplification drops 0.7% by 3DB.

15W Valve Modulator Amplifier circuit
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The deformation of the amplifier is approximately 8%. The T1 transformer has a primary impedance of 10KΩ, and the transformer ratio is about 1. Naturally, the transformer core is estimated at 15W. The power supply uses the 5U4 lamp as a rectifier. The power adapter has a primary 220V and secondary 2 x 300V for 150mA, 6.3V for 2A and 5V for 2A. The smoothing filter choke is 10H for 15mA. It is possible with this modulator to form from the protective grid a transmitter of up to 100 Watts, with a modulation depth of 90% to 100%.

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