Abstract: An electrical ground plane apparatus for a circuit board having an analog section and a digital section where the analog section of the circuit board has distributed thereon analog circuitry, and the digital section has distributed thereon digital circuitry. The analog section further has a connector which connects the analog circuitry to circuitry external to the circuit board. The circuit board is disposed within a chassis, which is operably connected to earth ground. The electrical ground plane apparatus includes an analog ground, a digital ground and a coupling circuit. The digital ground is operably connected to the analog ground at a location proximate the power supply connection and the analog ground is operably connected to the chassis through a coupling circuit. The coupling circuit is located proximate the connector so as to substantially minimize the flow of RF energy into the connector and, in turn, into the external circuitry.

Abstract: An improved method for correcting errors in a sequence of digital audio data for use in a system having a compact disc player device and a digital signal processor. A compact disc player device reads a compact disc and outputs digital audio data as a series of digitized samples and detects erroneous samples. An error correction apparatus implements a finite impulse response filter. The method achieves a low level of interpolation error within the corrected output of the finite impulse response filter by assigning zero-valued filter coefficients to digital audio samples that are likely to be erroneous due to their proximity to a known erroneous digital audio sample.

Abstract: An amplifier calibration apparatus for use in an audio device which processes an audio signal. The audio device includes a manual volume control for manually altering the gain of the signal. An amplifier which may include a digital potentiometer serves to alter the gain of the audio signal in response to a control signal. The amplifier calibration apparatus, which serves to automatically calibrate the amplifier, includes a controller; a waveform generator, which generates a known waveform, and a comparator circuit. The known waveform is fed into the amplifier and the resulting amplifier output is fed into the comparator circuit. The comparator compares a constant signal to the amplifier output resulting in a comparison output indicative of any difference between the two signals. The comparison signal is operably connected to the controller such that the controller can calibrate the full scale point of the amplifier.

Abstract: An improved CD transport apparatus wherein said apparatus incorporates a digital signal processor for processing digital audio signals read from a compact disc. The digital signal processor additionally serves to alter the gain of the digital audio signal when various control operations are commanded by the user so as to minimize audibility of extraneous noises which accompany such control operations and the potential damage which may be caused to audio components. The improved CD transport apparatus further includes a cueing switch for causing movement of the CD pickup only during movement of the cueing switch and a shuttle switch for causing movement of the CD pickup only when the shuttle switch is in an active position.

Abstract: A digital-to-analog converter--preamplifier apparatus serving as an interface between a source of digital audio signal data and an amplifier is disclosed. A digital stage receives multiple digital audio signal inputs, a selected one of which is analyzed by a digital audio interface receiver, processed by a digital signal processing device and a delta-sigma modulator prior to passing to the analog stage for conversion from the digital domain into left and right channel analog audio output signals. Volume control is performed on the audio signal in both the digital domain and the analog domain in order to optimize performance and minimize noise. The present invention automatically adjust for input word lengths of greater than 18-bits.