Abstract: An audio amplifier includes an output stage including a first toroidal transformer with a first pair of secondary windings that are coupled in parallel across an output terminal. The output stage further includes a second toroidal transformer with a second pair of secondary windings that are connected in a series combination that is coupled across the output terminal.

Abstract: An oscillator circuit comprises a push-push oscillator and a differential output, comprising a first and a second output circuit. The push-push oscillator has a first and a second branch. Each of the first and second branch comprises an own voltage divider branch of a common bridge circuit. Each of the first and second voltage divider branches comprises an own pair of micro-strip lines connected in series. Each of the first and second voltage divider branches has an own tap. Both taps are connected to each other by at least one of a first capacity and a micro-strip line. The differential output comprises a first and a second output terminal. The first output terminal is connected via the first output circuit to a first node. The second output terminal is connected via the second output circuit to a second node. Each of the first and second nodes of the push-push oscillator is a common node of both of the first and the second branches.

Abstract: The present disclosure relates to coupled circuits and methods of coupling circuits having a power supply wherein a plurality of transistors are inductively coupled directly to the power supply for providing a single DC supply voltage directly to each of the plurality of transistors, and wherein a plurality of transformers have primary and secondary windings, the primary and secondary windings providing, at least in part, inductive loads for inductively coupling the plurality of transistors to the power supply, the plurality of transformers also providing an AC signal path for coupling neighboring ones of the plurality of transistors together.

Abstract: A vacuum tube power amplifier with a user-operable switch and a single output transformer which selectively provides push-pull or single ended configurations for driving a loudspeaker.

Abstract: An amplifier is described including a pair of cathode-coupled pentode vacuum tubes. A first pentode of the pair includes a control grid configured to receive an input signal. A second pentode of the pair includes a control grid configured to be coupled to an input reference signal. A cascaded voltage regulator includes a first stage configured to generate a plate reference voltage for providing voltage to a plate of each pentode. The regulator includes a second stage configured to generate a screen reference voltage based on the plate reference voltage for providing voltage to a screen grid of each pentode. The amplifier can also include a push-pull output stage having a servo circuit configured to adjust the control bias signal for one of a pair of vacuum tubes included in the stage until the plate currents in the pair of tubes are substantially equal.

Abstract: An amplifier is described including a pair of cathode-coupled pentode vacuum tubes. A first pentode of the pair includes a control grid configured to receive an input signal. A second pentode of the pair includes a control grid configured to be coupled to an input reference signal. A cascaded voltage regulator includes a first stage configured to generate a plate reference voltage for providing voltage to a plate of each pentode. The regulator includes a second stage configured to generate a screen reference voltage based on the plate reference voltage for providing voltage to a screen grid of each pentode. The amplifier can also include a push-pull output stage having a servo circuit configured to adjust the control bias signal for one of a pair of vacuum tubes included in the stage until the plate currents in the pair of tubes are substantially equal.

Abstract: A musical amplifier that includes a vacuum tube and a transistor. The vacuum tube is connected to the gate of the transistor, so that the current flow through the transistor is controlled by the vacuum tube. According to one example of the invention, the vacuum tube-transistor arrangement is set up in a “push-pull” arrangement, where a vacuum tube-transistor combination controls positive voltages, and another vacuum tube-transistor combination controls the negative voltages delivered by the system, the system output being at approximately zero voltage when not under load. Also, the use of the “Edison effect,” referred to as “thermionic emission” from vacuum tubes to variably regulate output transistor bias current resulting in substantially reduced total harmonic distortion is also disclosed.

Abstract: A novel drive stage provides with low distortion a large amplitude signal, such as required for driving a cathode-follower output stage of a power amplifier. The drive stage comprises an amplification substage and a load substage. Each substage comprises two series connected vacuum tubes. Each substage is provided with a respective voltage divider network to provide that the two tubes of each substage share approximately equally both the quiescent static voltage and the dynamic voltage of the substage. The load substage coacts with the amplification substage to provide a novel mu-follower or SRPP circuit having approximately twice the voltage swing of a conventional circuit. This approximately quadruples the maximum power output of the cathode-follower amplifier.

Abstract: A cathode-follower power output stage is driven by a novel drive stage to provide with low distortion the large signal required to drive the output stage. The drive stage comprises two series connected vacuum tubes which share the large static and dynamic voltages of the drive stage so as to provide a drive signal having a large voltage swing, without generating audible distortion and without subjecting the drive stage tubes to excessively high voltages. The plate of a first drive tube is connected to the cathode of the second drive tube. A load impedance is connected from a B+ power supply terminal to the plate of the second drive tube. The grid of the second drive tube is driven by a signal responsive voltage divider network driven by the plate of the second drive tube.