Abstract: Class D amplifiers and methods dynamically modulate the transition zone of a square wave as a function of the input signal. Stated differently, the slew rate of the square wave is dynamically modulated as a function of the input signal. Stated in yet another way, at least one of the rise and fall times of the square wave is dynamically modulated as a function of the input signal. By dynamically modulating the transition zone of the square wave as a function of the input signal, a trapezoidal wave is produced, at least one of the rise and fall times of which are dynamically modulated as a function of the input signal. The trapezoidal wave need not have dead zones. This can reduce and preferably minimize switching losses. The slow rise and fall transition zone rates can also reduce and preferably minimize spurious switching noise at zero and low level modulation. Furthermore, damping network and diode losses may be reduced.

Abstract: An elongated, electrically conductive diaphragm is placed in a strongly magnetic field to produce a linear and an elongated sound source giving a high sound energy. At least two elongated diaphragms are positioned between intermediate and enclosing protected magnet elements, whereby the transverse length of the diaphragms are at least of the same size as that of the intermediate protected magnet elements. In this way, a sound without considerable interference merges at a short distance from the sources of the sound. By placing additional such sources of sound alongside each other, a broad sound source with a surface producing an essentially homogeneous sound field is achieved.