Controlling the performance of a thermionic tube
First Claim
1. A method of controlling the performance of a thermionic tube having a cathode, a plate and a grid that is configured to provide amplification of an audio derived signal including the application of a grid bias voltage to said grid, comprising the steps of:
- detecting the absence of an input audio signal; and
, in the absence of an input audio signal;
measuring output current between a cathode and a plate of the tube to identify an actual output current value;
comparing said actual output current value against a preferred output current value; and
adjusting a grid bias voltage so as to bring said actual output current value towards said preferred output current value.
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Accused Products
Abstract
Controlling the performance of the thermionic tube (102) having a cathode (103), a plate (104) and a grid (105) is disclosed. The tube is configured to provide amplification of an audio derived signal (106) and is arranged to apply a grid bias voltage to the grid. The absence of an input audio signal is detected whereafter output current between cathode and plate is measured to identify actual output current. The actual output current is compared against a preferred output current and the grid bias voltage is adjusted so as to bring the actual output current value towards the preferred output current value.
8 Citations
20 Claims
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1. A method of controlling the performance of a thermionic tube having a cathode, a plate and a grid that is configured to provide amplification of an audio derived signal including the application of a grid bias voltage to said grid, comprising the steps of:
detecting the absence of an input audio signal; and
, in the absence of an input audio signal;measuring output current between a cathode and a plate of the tube to identify an actual output current value; comparing said actual output current value against a preferred output current value; and adjusting a grid bias voltage so as to bring said actual output current value towards said preferred output current value. - View Dependent Claims (2, 3, 4, 5, 6, 7)
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8. An apparatus for controlling the performance of a thermionic tube when amplifying an audio signal, in which each thermionic tube has a cathode, a plate and a grid for receiving a grid bias voltage and, in use, said thermionic valves are attached to a circuit board within an audio amplifier comprising:
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a housing for attachment to a circuit board; power terminals for connection to a power supply; at least one input terminal for receiving a representation of actual output current between a cathode and a plate of a tube being controlled; at least one output terminal for supplying a grid bias voltage to said tube being controlled; a detection device for detecting the absence of an audio signal; and a processing device for comparing said representation of actual output current against a preferred output current value and adjusting the grid bias voltage so as to bring the actual output current towards the preferred output current when no audio input signal is present. - View Dependent Claims (9, 10, 11, 12, 13, 14, 15)
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16. An audio signal amplifier, comprising:
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one or more input terminals for receiving one or more audio frequency input signals; one or more output terminals for supplying one or more amplified output signals via one or more output transformers; a plurality of thermionic tubes, each having a cathode, a plate and a grid, in which the flow of current between said cathode and said plate is controlled by an input voltage applied to said grid and a bias voltage applied to said grid; and a performance control device for monitoring cathode currents when there is no audio input signal present and adjusting said grid bias voltages so as to adjust cathode current flowing through each thermionic tube. - View Dependent Claims (17, 18, 19, 20)
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Specification