Abstract: An audio amplifier is provided that adjusts the supply voltage rails communicated to a power amplifier circuit according to the circuit's output. The amplifier compares the output voltage from the power amplifier to a predetermined voltage range to determine if the output voltage is or is not within a predetermined range. If so, the audio amplifier reduces the supply voltage rails for the power amplifier circuit to reduced values. When the output voltage from the power amplifier moves outside the predetermined range, the supply voltage rails return to maximum levels. Whenever the output voltage from the power amplifier is not within the predetermined range, the audio amplifier maintains the supply voltage rails at maximum levels. By reducing the supply voltage rails for the power amplifier circuit, less power is dissipated by the power amplifier circuit, thereby generating less heat in the audio amplifier.

Abstract: An audio amplifier drives a load in the form of a sound producing loud speaker exhibiting a frequency variable impedance characteristic over a range of audio frequencies. Voltage and current feedback circuits respectively establish a minimum voltage feedback and a discrete feedback characteristic. A presence feedback circuit coupled to ground reduces feedback in discrete steps with increasing frequency above a selected level and a resonance feedback circuit coupled in parallel with the amplifier circuit coupled in parallel with the amplifier reduces voltage feedback in discrete steps with decreasing frequencies below a selected level. The controls are responsive to a digital interface for providing discrete settings.

Abstract: An audio amplifier drives a load in the form of a sound producing loud speaker exhibiting a frequency variable impedance characteristic over a range of audio frequencies. Voltage and current feedback circuits respectively establish a minimum voltage feedback and a discrete feedback characteristic. A presence feedback circuit coupled to ground reduces feedback in discrete steps with increasing frequency above a selected level and a resonance feedback circuit coupled in parallel with the amplifier circuit coupled in parallel with the amplifier reduces voltage feedback in discrete steps with decreasing frequencies below a selected level. The controls are responsive to a digital interface for providing discrete settings.

Abstract: An enclosure has one or more loud speakers therein adjacent the front of the enclosure; and the back of the enclosure defines an opening. A pair of tilt members are mounted on inner surfaces of the enclosure at opposite sides thereof for sliding and rotating movement with respect to the enclosure. The tilt members each include an elongated straight portion and an offset portion at one end of the straight portion. The tilt members are stored completely within the enclosure and may be adjusted to extend through and rearwardly of the opening at the rear of the enclosure to engage a support surface. A locking member locks each tilt member in adjusted position. Electronic means for operating the loud speakers may be disposed within the enclosure at the top thereof.

Abstract: In a power amplifier, a control device employing a dual ganged potentiometer is connected in the feedback circuits of successive amplifier stages to increase the gain of the front end stage while simultaneously reducing the gain in a subsequent stage when the control is turned down. A distortion circuit, such as a tube compression circuit, is coupled between the stages. When the control is turned down, the compression circuit is activated at a lower level that effectively reduces the output power of the second stage. Presence and resonance controls may be provided to tailor high and low frequency damping factor of the second stage and function until the compression circuitry is activated. A ripple reduction filter is provided in a filtered supply for the drivers in the second or power amplifier stage.

Abstract: A multi-stage solid state amplifier emulates the distortion associated with grid current flow in a multi-stage tube amplifier by means of a clipping device in the circuit between each series connected stage. In a particular embodiment, each stage includes a field effect transistor (FET) and the clipping device is a diode.

Abstract: A multi-stage solid state amplifier emulates the distortion associated with grid current flow in a multi-stage tube amplifier by means of a clipping device in the circuit between each series connected stage. In a particular embodiment, each stage includes a field effect transistor (FET) and the clipping device is a diode. In another embodiment, each stage includes a Darlington connected pair of transistors. An input diode and a multilevel biasing circuit emulates a tube circuit input.

Abstract: The present invention employs gain compensation such that when the amplifier is in the clean mode, the gain is at a selected level and when the amplifier is in the lead mode gain is decreased. In one embodiment a selectable brightness control is employed to raise the high frequency response in the clean mode. In another embodiment, a selectable gain boost control is employed to increase the gain in the lead mode. At least one frequency selectable means is provided in a post distortion stage output circuit for varying the frequency response of the output in the lead mode.

Abstract: Separate audio amplifier channels are provided with separate input signal level controls so that the output of one channel is unaffected by the input signal level of the other channel, and vice versa. A switch controls selection of the desired channel. Three channels also be provided and first and second switches control selection of any one of the three channels. As before, separate input signal level controls are provided for the three channels so that each is unaffected by the signal level control of either of the others. Two channels may be distortion channels, each with an input level control and also with an output level control. One channel may be a clean sound channel.

Abstract: Separate audio amplifier channels are provided with separate input signal level controls so that the output of one channel is unaffected by the the input signal level of the other channel, and vice versa. A switch controls selection of the desired channel. Three channels may also be provided and first and second switches control selection of any one of the three channels. As before, separate input signal level controls are provided for the three channels so that each is unaffected by the signal level control of either of the others. Two channels may be distortion channels, each with an input level control and also with an output level control. One channel may be a clean sound channel.

Abstract: An amplifier circuit for use with a guitar. It has two modes, a "clean" output mode, and a "super-distortion" mode, which mode has independent gain control prior to a distortion stage. There is also post distortion gain control.