/Long time lurker, registered to ask this question because **the internet doesn't know**.

I have been looking around for some information on how PCM actually works. I'm quite comfortable with the Nyquist criterion and all the frequency-related jazz, but I'm still a bit stuck on the word-size and dynamic range.

I know the decibel is dimensionless quantity, and is used as a relative scale. In some applications, dBm is used, where 0dBm=1mW. There are a bunch of others with different reference values, but as far as I know 'dynamic range' uses the dB unit as a relative measurement, where 0dB is the peak of the signal. Is this correct?

In this case, what exactly is 0dB? is 0dB simply the voltage roof of the ADC used in the recording studio? And sound engineers manipulate the gain such that the highest peaks reach just below 0dB? (I understand more mastering can be done after this, but theoretically that would reduce the dynamic range slightly. Anyhow, most listeners won't notice the difference anyways.)

After mastering (ideally), the highest peaks will reach 0dB without clipping, and the lowest -96dB represents the lowest 'volume' which can be encoded. Is this the goal?

Also, why does +1-bit = +6 dB dynamic range? An extra bit of word length will double the resolution, that should give +3 dB of dynamic range (the lowest 'volume' limit is halved --> the lowest point in dynamic range decreases by 3dB).

Thank you in advance, and Merry Christmas.