805 Vacuum tube transformer push power amplifier circuit

Published:2011/5/13 4:49:00 Author:May | Keyword: power amplifier, Vacuum tube, transformer push | From:SeekIC

The 805’s features of high essential resistance leads to that the inductance value output transformer needed is larger. In addition, the other problem caused by it is that output impedance is too high and damping coefficient is decreased. It is a common 805 circuit without transformer secondary sampling negative feedback. Its damping coefficient is 10K/tube essential resistance (10K)=1 and is lower when output transformer’s primary impedance is 10K. And it is lacking proper controlling force to speaker. Low frequency has lager quantity but low quality. Also, the damping coefficient of 300B vacuum tube with 700Ω essential resistance is 3.5K/700Ω=5 and it has effective controlling force to speaker when it adopts 3.5K output transformer. So, the 805 class essential resistance tube should add negative feedback which the sampling point is output transformer’s primary, and the familiar is negative feedback loop. It can make the essential resistance of 805 decreasing some by suitable decreasing the working voltage (suitable decrease output power) and improving 805 working current (with litter influence the designing and making of output transformer). But it is not the main method.



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