Abstract: A sub-harmonic generator includes: an input filter operable to receive an input signal containing frequencies from among a first range and to produce a first intermediate signal containing frequencies from among a second range; a signal divider circuit operable to receive the first intermediate signal and to produce a square wave signal containing square wave signal components at fundamental frequencies from among a third range, the third range of frequencies being about one octave below the second range of frequencies; a wave-shaping circuit operable to receive the square wave signal and to produce a second intermediate signal containing sinusoidal signal components from among frequencies corresponding to the respective fundamental frequencies of the square wave signal components; an RMS detector operable to produce an RMS signal corresponding to an instantaneous amplitude of the first intermediate signal; and a voltage controlled amplifier operable to amplify the second intermediate signal by an amount prop

Abstract: A bridge for attaching strings to a musical instrument. The bridge has a body comprised of a base and a main portion with saddle chambers formed in the main portion. Holes are formed within the saddle chambers. Each saddle chamber houses a saddle members therein. The saddle members have adjusting elements that both adjust the position of the string by changing the position of the saddle member, and adjust the position of the string on the saddle member. A plurality of coupling screws secure the bridge to the body of the instrument. Strings are threaded over the saddle member, through the bridge and out through the compression screws where they are secured or knotted.

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: A guitar bridge having a body comprised of a base and a main portion with a plurality of slots formed in the main portion of the body. A plurality of holes are formed in the body and located within the plurality of slots. A resonance chamber is formed in the main portion of the body. A plurality of coupling screws secure the body of the bridge to the body of the musical instrument. Strings are threaded through the bridge and through the compression screws so that dual compression of the bridge is achieved with the use of a two-way pressure system formed by the pressure of the coupling screws and the instrument strings.

Abstract: A digital amplifier having an input for receiving an input signal employs an oscillator for producing a reference pulse signal and a sawtooth signal. A first generating circuit coupled to the oscillator is responsive to the reference pulse signal for producing a first pulse signal of a first polarity. A second generating circuit coupled to the first generating circuit is responsive to said first pulse signal for producing a second pulse signal of a polarity opposite the first polarity. A comparator responsively coupled to the input and said oscillator compares the input signal and the sawtooth signal and produces a comparator output signal operable between first and second states, for toggling the comparator output signal between the first and second states each time the input signal equals the sawtooth signal. The comparator output is maintained in the first or second state when the input signal exceeds the sawtooth signal.

Abstract: A remotely controlled microphone amplifier has a first amplifier stage with a variable gain circuit operatively connected in the overall feedback loop of the first stage for controlling the gain in first increments. A unity gain second amplifier stage has variable attenuator operatively coupled between the output of the first amplifier stage and the input of the second amplifier stage. The variable attenuator controls the input to the second stage in second increments less than the first increments. The overall gain is linearly adjustable and varies in equal increments.

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: A phase plug for a horn loaded speaker has a frustro-conical body with a spherical entrance end and a planer outlet end. The plug is formed with radial channels. The entrance of the phase plug and the speaker diaphragm are conformal and the channels have generally equal aperture area from the entrance to the outlet, or slightly increasing aperture areas so as to minimize diffraction The truncation surface is defined by the intersection of the sidewalls of the conical body and the cone angle of the horn.

Abstract: A loudspeaker horn has straight wall section and a curved wall section. The straight wall section has diverging walls defining a coverage angle and the curved wall portion is connected to the straight wall portion at a point tangent thereto, and has a proximal end disposed perpendicular to the plane of the throat entrance. At least one coverage angle in orthogonal planes has a common apex in the plane of the throat entrance and along the horn axis.

Abstract: A circuit for increasing damping factor in an audio amplifier adapted to be coupled to a load by output feed and return leads and components having an impedance causing a reduction in the damping factor, employs a balanced feedback network having first and second inputs and first and second outputs. The first input is coupled to a selected one of the feed and return lead near the output terminal and the second input is coupled to the same lead remote from the output terminal to thereby establish a series impedance between said first and second inputs representative of impedance of the selected output lead. The first output is coupled to the non-inverting input of the amplifier and the second output is coupled to the inverting input of the amplifier. The balanced feedback network positively feeds back a representation of the impedance to compensate therefor and thereby raise the damping factor of the amplifier. In an alternative embodiment, an isolating transformer is employed in the balanced feedback network.

Abstract: A compound differential circuit detects the highest relative signal of a plurality of input signals. Peak detector circuits including a sensing diode and a capacitor, are employed to produce a control signal. A switch receives the corresponding control signal. One switch is active at a time in response to the highest control signal. An LED connected to the activated switch is illuminated so that a visual indication of the highest input signal is displayed. In another embodiment, a feedback sensor for a graphic equalizer is disclosed.

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 power amplifier has a distortion control circuit responsive to a clipping detector for loading said amplifier input with a signal sufficient to reduce the input to the tube grids to a level below clipping.

Abstract: A proportional, multichannel gain sharing audio circuit has a gain control in the computing leg so that additional weight may be accorded the channel so that the channel is allocated greater gain in proportion to the total amount of signal available to all of the channels combined. Weighting may be adjustable and more than one channel may have such a feature, so that a hierarchy of priority is possible.

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: A drum having improved acoustic characteristics includes a rigid annular bridge at one or both ends of a thin resonant annular shell attached to the bridges. A drum head is mounted on the bridge by a tension mechanism attached only to the bridge, and the drum is mounted on a drum stand by mounting hardware attached only to the bridge, leaving the shell free of load bearing and tensive and compressive forces and making the shell resonate more effectively. The bridge is machined from a solid block of wood formed of horizontal laminations. A microphone can be mounted on the inside of the bridge, with electrical leads exiting the drum through the mounting hardware. A snare drum having a thick body instead of a resonant shell is machined in the same way and has internal head tension members that make it possible to have a thicker body.

Abstract: An augmentation amplifier includes a first power amplifier stage having an output adapted to be coupled to one side of a load. A second amplifier of negative unity gain has an output coupled to the input adapted to be of the first amplifier and its input coupled to the other side of the load. The circuit may be switched to bypass the bridge and modular units may be employed together. The system is particularly adapted for a powered speaker system for use with a computer sound card.