Differences between analog and digital

Answer 1

A great question!

We hear much about digital and analog signals and most people know nothing about the difference. Let's try to give some simple basics.

A digital piece of electronics is either on, or it is off, Black or white with no gray in between. Early electrical devices used 5 volts circuitry. If the five volts was there, we had a digital "on" condition. If the 5 volts was not there, we had a digital "off" condition. We could use this in many ways. One way was to call the "on" condition a mathematical "1" and the ansence if the voltage a "0". That means we could make electrical devices count to one! BIG DEAL? well, yes it was because that is how every computer out there works, as well as how the internet transfers all this cool stuff!

Analog is everything in between the "0" and the "1" of digital electronics. This an probably the most interesting area for most engineers that really know electronics. You may be able to save audio information in digital form, but your ear sure wants to hear it in analog. The ability to vary voltages between the full on and off of the divice requires more currents and more design abilities. All actual transmission of every radio or television signal is done through and analog transmitter. When you hear about the end of analog television and the new digital transmission, they are actually discussing the input to the analog transmitter.

The ability to decode digital transmissions on this analog signal allows us to use much more of the transmission band for the given device. A television signal that could only put out maybe 7 signals in analog now can carry many signals. That television station you are watching could also be sending a great deal of other information out! Even in analog we could send a dozen different things out "behind" that signal you could hear and see. "Muzak" (the elevator music) goes out "behind" these tv or radio signals (called sub carriers). Digital encoding of this information allows for many many times the sub carriers on a given station.

Answer 2

Analog signals are linear. This means there is an infinitely small variation between any two moments of the signal. Digital is a discrete step between to moments. There are two main things to consider when describing a digitally generated wave. Sample rate and bit resolution. Sample rate is the amount of time spent at a single plateau, while bit resolution is the number of steps between minimum and maximum.

If we have an ADC (Analog to Digital Converter) or DAC (Digital to Analog Converter) that can sample at 10 Hertz (WAY low frequency), there will be 10 discrete plateaus in the signal being recorded every second. If the ADC is a 2 bit converter, there would be 4 discrete steps in the recorded signal. These settings are unrealistically low, only to simplify the procedure. If the ADC/DAC is 12bit, there would be 4096 discrete steps between minimum and maximum. If they are 16bit = 65536 steps. 24bit = 16777216 steps. Any of these running at 10 Hz would be extremely crappy sound, so the sample rate has to go up. At 100 Hz, the sound would still sound like garbage. 1000 Hz starts to make a pure tone sound okay, but a complex set of sounds like a Rock song would be pretty unrecognizable. 10000 Hz start to hear the lower frequencies of the song better. 100000 Hz and the complex sounds of the song start to be recognizable.

A rule of thumb is 10 times the signal you are trying to digitize makes an acceptable recreation. Our high end of hearing is 20000 Hz and some of us can't hear that while others can hear a little higher frequency than that. So using our rule of thumb, a 200000 Hz ADC/DAC would be high enough quality that 90% of the population would not be able to distinguish between a digital and analog representation of the same song.

Answer 3

The difference between analog and digital lies in the method of translation. When a speaker makes noise, it is because it receives a certain amount of voltage (either to trigger the sub-woofer, treble amp, or pre-amp. The differences in sound are not as important as the way they are generated). Analog noise is just the pure sound you here when music comes from your speaker. It is the voltage. Analog would be an electrical signal from a bass, or pure electrical voltage from a mic. In this method, no digital translators are used (computers, etc.). The signal goes from instrument to amp, voltage through and through.

In a digital recording setup, one encounters digital translators, such as synthesizers or computers. Digital sound is purely 0s and 1s, or binary. Digital recording involves a step in which the sound that was played is no sound at all, but rather language to a computer. It then translates this back into voltage and sends that to a speaker or amp.

So what are the differences in sound quality? you may ask. The answer is highly debatable. Many will tell you that analog will always be better than digital. Many will say the opposite. Take it all with a grain of salt. Many will cite records, vinyl that is, as the evidence for a "purer," or "warmer" sound in analog recording. However, this is an effect produced both by the tape it was recorded on to (often a crackly sound is produced by imperfection), and the method by which it is played. If a digital recording were to be put on a record, many of these imperfections would cross over. Moreover, with the new bounds in digital technology, this sound could be built into a track with a good set of effects. So, what are advantages of digital sound? Clarity. The computer will always know what the sounds should sound like when they exit the speaker. This means it can correct imperfections on the way and produce undistorted and clear end-product. Many will say that this sounds too perfect, though, and is not natural. I would tend to agree, but that is personal opinion.

Overall, the difference in the end is small. Most people are not trained enough to hear the difference, and even as a sound engineer, I am hard-pressed to hear the difference between any new track that was recorded with an analog system and the same track recorded digitally. All in all, it comes down to the quality of equipment and the quality of the person behind the desk and at the board. As I said, take it with a grain of salt. Most of all, you be the judge! Listen to a record, listen to an MP3. See if you can recognize any of the imperfections of analog, and any of the roboticness of a digital track. If not, don't worry about, and just let the silly sound engineers have their argument.