Amplifiers – With control of power supply or bias voltage – Control means for anode of screen grid circuit
Patent
1990-08-10
1992-02-25
Mullins, James B.
Amplifiers
With control of power supply or bias voltage
Control means for anode of screen grid circuit
330202, 381118, 381120, H03F 100
Patent
active
050917005
ABSTRACT:
A method enables a musician to reduce the voltage level between a nominal level which is supplied to power an audio power amplifier including at least one vacuum tube power output device and a reduced level, by controlling AC input voltage level of an AC to DC power supply via an input transformer having a primary winding connected to receive nominal AC voltage from the AC power mains, a high voltage secondary, and a low voltage secondary for directly supplying heater power to the vacuum tube power output device. The method comprising the steps of: overwinding the primary winding of the input transformer with respect to the AC voltage level of the supply mains, providing a tap in the overwound primary at a location which corresponds generally to the AC voltage level of the supply mains, and providing a switching means for switching between the tap corresponding to the AC voltage level of the supply mains to provide nominal full power supply to the audio power amplifier to achieve nominal sound reproduction characteristics during musical play, and the full winding of the overwound primary in order to provide a fraction of the AC voltage level of the supply mains to provide reduced power supply to the audio power amplifier to achieve altered sound reproduction characteristics during musical play.
REFERENCES:
patent: 2082478 (1937-06-01), Beers
patent: 4211893 (1980-07-01), Smith
patent: 4701957 (1987-10-01), Smith
patent: 4713624 (1987-12-01), Smith
Harrison David B.
Mullins James B.
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