[RRod]

  I think you need at least 20 bits to get certain sounds like the cannons in the 1812 Overture without compression. (http://imgur.com/a/CFf70)

 
Even if you record the cannon with more bits, you still have the reality of mixing that sound into a track that is meant for humans to listen to in a reasonable listening room.
 
Re Audacity and 50dB gain: I think it's just a limit they set so that you ask yourself the question "Should I really be applying ±50dB gain to this?"

 

[stalepie]

   
G

 
Thanks for that great response. It all sounds similar to what I'd learned before, like from Monty's presentation at Xiph, but I somehow keep forgetting it. I don't think I'm smart enough to really understand these topics.
 
I had not heard that about analog noise floor from the electronics in a synth, or electrons making noise when colliding. 

 

[gregorio]

  [1] Thanks for that great response.
 
[2] I had not heard that about analog noise floor from the electronics in a synth, or electrons making noise when colliding. 

 
1. No problem, you're welcome.
 
2. It's called thermal or Johnson noise and exists in all electronic circuits. By about 25 years ago digital audio had advanced to the stage that Johnson noise was the limiting factor. In reality there is no such thing as 24bit audio, only a 24bit audio container. Analogue to digital converters and digital to analogue converters by definition contain analogue sections and the Johnson noise generated in these sections exceeds the limits which 24bit audio would otherwise be capable of. When using an ADC or DAC, at least the last (least significant) 3 bits will only be Johnson noise. So even just in theory, the most which can be accomplished is 21bit digital audio. In practise this is not such a severe limitation as it may seem because Johnson noise is relatively insignificant compared to the noise introduced by the transducers or in comparison to acoustic noise floors. In an entirely analogue signal chain, we obviously have a considerable number of electronic components and therefore of Johnson noise and indeed, this was one of the main reasons why digital audio was invented in the first place.
 
G