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 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: In this hybrid amplifier circuit the vacuum tube is direct coupled or DC coupled to the output of a solid state amplifier in a cathode follower configuration. An automatically operative bypass component, such as a Zener diode, LED, transistor junction or relay, diverts the signal output of the solid state amplifier around the vacuum tube stage when bias conditions or other vacuum tube operating conditions signify that the vacuum tube is still warming up or for some reason inoperative. Thus the hybrid circuit produces amplification at full volume and at low distortion even while the vacuum tube is warming up. The vacuum tube provides a desirable warming coloration to the sound that may be user adjusted by controlling the level of closed loop feedback within the circuit. Lower total harmonic distortion is achieved in a pentode vacuum tube device by direct coupling the screen and control grids. Lower voltage use of power pentodes wired in nonconventional "triode mode" is achieved.

Abstract: The direct coupled solid state-vacuum tube hybrid circuit matches a high impedance audio source to a low impedance audio destination. The resulting device supplies essentially unit gain and has both single ended and balanced outputs. The solid state operational amplifier and vacuum tube devices are DC coupled and supplied from a common low voltage DC power supply. The vacuum tube is incorporated directly in the feedback loop of the operational amplifier and a suitably chosen dampening resistor allows the circuit to provide vacuum tube characteristic warming effects without unwanted distortion or tube microphonics.

Abstract: The distortion pedal for electric guitar and other electronic musical instruments employs vacuum tube circuitry operated by low voltage "battery eliminator" DC power supply. A pull-up resistor biasing circuit on the vacuum tube grid improves input and output impedance and circuit headroom while providing good control over the harmonic content and sustain.

Abstract: A closed loop bipolar transistor driver is coupled to an open loop MOSFET output stage. The closed loop driver amplifier operates within a higher voltage range than the open loop MOSFET output amplifier. The closed loop driver stage is capable of driving the MOSFET output stage into saturation and the MOSFET output stage thereby produces a desirable vacuum tube-like sound characterized by warm, even harmonics. Feedback is used to maintain the closed loop driver circuit in a linear operating regime thereby preventing undesirable hard clipping associated with bipolar transistors when they are overdriven.