This invention relates to a novel method and means for improving the quality of audio sound produced by digital recordings, and more particularly to a combined signal splitting and delay device for removing time domain errors and the like from signals produced by digital audio reproduction systems.
The field of audio recording and reproduction has reached extremely sophisticated levels. At the same time, listener sophistication likewise has increased to the point where serious audiophiles can detect even the slightest distortion in the output of contemporary audio equipment--including, compact disc equipment. Much of the more sophisticated audio equipment currently available in the marketplace is designed to produce a digital rather than an analog recording. While much improved over that of analog signal recordings, nevertheless the signal output of a digital recording, for example, the output from a compact disc player, because of undesirable phase shift, often includes time domain errors which can be displeasing to the above-noted audiophiles.
There are currently available in the marketplace some devices for removing or minimizing time domain errors of the type described, but most of this equipment is extremely expensive, and is designed to process the recorded digital signals in the digital stage. The Wadia Digimaster X-32 digital decoding computer, for example, is designed to solve some of the above-noted problems, but is very expensive and is quite large dimensionally.
As referred to hereinafter, the term "sampling frequency" means the informational sampling frequency at which an analog signal is sampled by the A/D converter which is used to convert an analog signal to a digital signal for the purpose of producing a digital recording of that analog signal. For example, for producing a compact disc recording the sampling rate or frequency normally is approximately 44.1 kHz., while for production of a digital audio tape this frequency is approximately 48 kHz. In any event the sampling frequency or rate as used in connection with this invention is not to be confused with the technique of over-sampling which normally occurs at higher frequencies.
It should be noted also that the sampling frequency utilized in the production of digital recordings also has the effect of introducing some slight, undesirable phase shift in the reconstructed analog output signal which is produced by a D/A converter from a digital recording. This phase lead can result in some slight distortion of the reconstructed audio signal.
Accordingly, it is an object of this invention to provide an improved signal processing method for removing undesirable time domain errors from the output signals of digital recordings such as CD players and the like.
A more specific object of this invention is to provide a novel device of the type described which splits and processes the analog signal produced by a digital source, thereby to improve the resulting audio sound.
Still another object of this invention is to provide a device of the type described which is substantially more inexpensive and simpler to produce than prior signal processing devices.
Other objects of this invention will be apparent hereinafter from the specification and from the recital of the appended claims, particularly when read in conjunction with the accompanying drawings.