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Bit Depth and Noise
Old 15th October 2014
  #1
Gear Addict
 

Bit Depth and Noise

Hi guys.

Just a question on the digital domain and how it represents the analogue signal.

Ok so I know how magnetism is used to represent an audio signal in the old analogue world and that the noise, we know as hiss comes mainly from the electronic circuitry.
My Question is how a digital device is built to represent that same signal as soon as it hits the A/D converter. I know that there has to be a compromise between bit depth and sample rate. A signal can be represented by 1bit if oversampling is used but I'm slightly confused when it is said that 1bit represents 6dB. Is each dB relative to analogue voltage level where the converter gives it a certain binary code? Is binary code represented by a set of gates?
Further to this, does the noise of the digital world come from the time where sample rate and bit depth is not active? The point in between each sample rate so to speak. Why would 24 bit be less noisy compared to 16 bit.

Thanks and I hope I'm clear on what I say!!
Old 16th October 2014
  #2
Gear Guru
 
kafka's Avatar
The number of bits represents an upper limit on the S/N ratio in a conversion. A 16-bit converter can only chop the signal into 2^16 equal levels, so it is inherently noisier than a 24-bit converter, which can do 2^24 equal parts. 24-bit converters typically exceed the noise specs of the analog circuitry around them, so you're actually getting only around 20 bits or so of real conversion.

Also, when you're talking about 1-bit converters, understand that there's an additional level of processing, called delta-sigma modulation, that's done before the conversion. That's a whole another ball of wax.

A forum may not be the best way to get this understanding, given the difficulties of explaining it, and the amount of misunderstanding there is out there. A better way might be to do some background reading. Here's a start:

https://www.applied-acoustics.com/te...eratebitdepth/
http://en.wikipedia.org/wiki/Audio_bit_depth
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