Free Pony Theory ~ Limitation of Vinyl

Joined: 23 Sep 2006 Posts: 1088

Next limitation: treble. You can put as much treble on a DAT or CD as you want. Unfortunately this is not true on a record (or analog tape for that matter). Although 25kHz response is possible, excessive transients are a problem. There are several reasons for this. It was decided with the advent of the first electrical transcription phonograph record, to reduce bass and boost treble in the cutting of the master record. This reduces bass wiggles and makes treble louder. And we aren’t talking about a little bit of cut and boost here, we’re talking about a 40 dB change from bottom to top! Without the bass cut, you’d only have about 5 minutes on your LP side. Without the treble boost, you would hear mostly surface noise. You don’t have to worry about this drastic cut and boost sounding funny, because the phono preamplifier in your amplifier or receiver has an inverse curve which boosts the bass and reduces the treble by the same amounts used in cutting, so the whole process comes out linear. This was standardized worldwide in 1953 and is called the RIAA record and reproduce curves.

http://www.recordtech.com/prodsounds.htm

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Joined: 23 Sep 2006 Posts: 1088

The very nature of the analog signal leads to its own shortcomings. In the analog domain, any waveform is allowable; therefore the playback mechanism has no means to differentiate noise and distortion from the original signal. Further, in an analog system every copy made introduces more noise than its parent. This fact is due to both the playback and recording mechanism which must physically contact the media, further damaging it after every pass. Every analog system also carries the side effect that the total system noise is the summation of all distortion and noise from each component in the signal path. Finally, analog equipment is of limited performance, exhibiting: an uneven frequency response (which requires extensive equalization), a limited 60 dB dynamic range, and a 30 dB channel separation--which affects stereo imaging and staging.

The need for a new audio format is apparent, and digital audio fills the performance shortcomings of analog audio. The beauty of the digital audio signal is that noise and distortion can be separated from the audio signal. A digital audio signal's quality is not a function of the reading mechanism nor the media in a properly engineered system. Performance parameters such as frequency response, linearity, and noise are only functions of the digital-to-analog converter (DAC). Performance parameters indicative of a digital audio system include full audio band frequency response of 5 - 22,000 Hz, 90+ dB dynamic range, and a flat response across the entire audio band.

The final strength of digital audio is the circuitry upon which it is built. First, due to a large degree of circuit integration digital circuits do not degrade with time as analog circuits do. Further, for all practical purposes, a digital signal will suffer no degradation until distortion and noise has become so great that the signal is out of its voltage threshold. However, this threshold has been made intentionally large expressly for this reason. The high level of circuit integration also means that for the same given task, the digital circuitry will cost far less than its analog counterpart.

http://www.tc.umn.edu/~erick205/Papers/paper.html

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