Abstract: An audio amplifier and speaker system are stacked and magnetically coupled together. The audio amplifier is coupled for receiving an audio signal. A first securing assembly is provided on a bottom surface of the amplifier. The first securing assembly may be a foot formed on the bottom surface of the audio amplifier. The speaker is electrically coupled to the amplifier. A second securing assembly is provided on a top surface of the speaker. The second securing assembly may be a receptacle formed in top surface of the speaker. The foot is inserted into the receptacle. The foot and receptacle are magnetically coupled to attach the amplifier to the speaker. The foot has a first electrical connector, and the receptacle has a second electrical connector mated to the first electrical connector to route the audio signal from the amplifier to the speaker.

Abstract: A musical string instrument (12) has a body (21) with a resonate cavity covered by a soundboard (22). A pick guard (34) has a flat surface for mounting to the soundboard of the instrument. Electronic control components (36) are mounted within a housing of the pick guard. The musician can control a preamplifier within the resonate cavity of the body with knobs (58) and push buttons (60) located on the pick guard. A thin, flat, multi-conductor ribbon cable (38) is connected to the electronic control components and routed along a surface of the soundboard and through a sound hole (24) in the soundboard into the resonate cavity of the body. The ribbon cable entering the resonating cavity through the sound hole does not adversely effect the natural response, performance, sound quality, and tonal property of the string instrument and does not require any additional holes be drilled in the soundboard.

Abstract: An input signal is applied to a notch filter having a transfer function that is the inverse of the expected noise signal. The filtered signal is coupled to a first amplifier and the input signal is coupled to a second amplifier. The outputs of the amplifiers are summed. The gains of the amplifiers are oppositely adjusted in response to the magnitude of the input signal. At low amplitude, the filtered signal is amplified more than the unfiltered signal. At high amplitude, the unfiltered signal is amplified more than the filtered signal.

Abstract: A musical string instrument (12) has a body (21) with a resonate cavity covered by a soundboard (22). A pick guard (34) has a flat surface for mounting to the soundboard of the instrument. Electronic control components (36) are mounted within a housing of the pick guard. The musician can control a preamplifier within the resonate cavity of the body with knobs (58) and push buttons (60) located on the pick guard. A thin, flat, multi-conductor ribbon cable (38) is connected to the electronic control components and routed along a surface of the soundboard and through a sound hole (24) in the soundboard into the resonate cavity of the body. The ribbon cable entering the resonating cavity through the sound hole does not adversely effect the natural response, performance, sound quality, and tonal property of the string instrument and does not require any additional holes be drilled in the soundboard.

Abstract: An input signal is applied to a notch filter having a transfer function that is the inverse of the expected noise signal. The filtered signal is coupled to a first amplifier and the input signal is coupled to a second amplifier. The outputs of the amplifiers are summed. The gains of the amplifiers are oppositely adjusted in response to the magnitude of the input signal. At low amplitude, the filtered signal is amplified more than the unfiltered signal. At high amplitude, the unfiltered signal is amplified more than the filtered signal.

Abstract: A combination of limited data, 3D linear interpolation, and a unique simulation circuit are combined to provide a programmable tone control that can simulate any desired tone stack. In accordance with one aspect of the invention, it has been found that a reduced number of data points plus interpolation provides sufficiently accurate coefficients for simulation. The data points are obtained from measurements of the actual operation of the analog tone stacks to be simulated. A second aspect of the invention is the simulation circuit controlled by the coefficients to accurately reproduce the operation of any given tone stack. The simulation circuit uses two programmable filters and three variable gain amplifiers to simulate a tone stack. The cut-off frequency of each filter and the gain of each amplifier are determined by coefficients extracted by interpolation from stored data.