Why is there a need to convert analog signals to digital? — Ankit, Gwalior, India
Marshall Brain Answers:
One reason is to avoid degradation and corruption of the signal. This is one reason why CDs (which are digital) are preferred over vinyl records (which are analog). On a vinyl record, the pressure of the needle eventually wears away the groove and degrades/corrupts the music on the album. On a CD, the digital data that the laser is reading is either correct or incorrect, and a digital device can know if the data is incorrect using things like checksums. Then, if it is incorrect, error correcting codes can be used to retrieve the valid data.
Another reason is a lack of noise. On a vinyl record or a cassette tape (which are analog), there is some amount of hiss that corrupts the analog signal because of the physical media. A CD has no hiss because the digital signal is immune to this effect.
A third reason is compression. With digital data there are a variety of compression algorithms that can be used to shrink the signal. An MP3 file is much smaller than the uncompressed song on the CD, but the sound quality is still good. Cell phones and DVDs also depend on compression. Without compression, it would be impossible to fit a movie on a DVD.