| Recording Tip#18 |
| Recording Basics Part 5 |
| Getting the Best Recording Quality |
| Daniel Dennis |
| Digital Recording |
| With digital recording, the truism is that the longer the digital word (the more 1s & 0s), the better the quality. And that's true. |
| The signal to noise ratio of a 16-bit recording (CD quality) is about 92 dB. That means that the signal is 92 dB (40,000 times) as loud as the noise created in the digital process. (By the way, this does not mean that the signal is 92 dB louder than ALL noise, just 92 dB louder than the noise created by the process.) The signal to noise ratio of a 24-bit recording is 144 dB (the signal is over 15 million times the noise level). |
| The diagram below may give you an idea of how digital word length can effect quality. |
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| Input vs. Recording Quality |
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| What Does it Mean? |
| The thing about it is that digital audio is sampling: the waveform is not recorded as in analog but only slices are recorded every 44100 times a second or 48000 times a second or 96000 times a second. The voltage at the time that the sample is taken is the voltage that gets recorded. However, how many different levels can be recorded is according to how long the word is. With 8 bit audio, there are 256 possible voltages (Space Invaders was 8 Bit). With 16 Bit, it's 65,536 (typical CD). DVDs that have 24-bit can record over 16,000,000 possible voltages. So the longer the word, the more precise the signal recorded. |
| Proper Levels |
| One of the main mistakes made by inexperienced engineers is in level. |
| In digital recording, it is true that too high of a level is very bad. What happens is that the system does not have numbers to define voltages over 0 dB. As a result, the recording of such a signal is just distortion - with no real relation to what the original signal was. |
| The other problem with level is when they are too low. |
| What most people don't realize is that there is a 1-bit loss of quality for every 6 dB below 0 that a signal is recorded. While this is not much of an issue with 24 bit recording, with 16-bit recording this can be a big problem. With a recording done with the meters peaking at 1/2 the displayed level (about -18 dB), your result would be a 13-bit recording - very low quality with grunge. |
| So, although it is not a good idea to record with the level too high, it is also not a recommended strategy to record the levels too low. |