Quote:

Originally Posted by

**theblue1**
First, I think you've 'apologized' in advance for any lack of knowledge, so, hopefully that will provide you some insulation here... heh

Moving right along, you seem to have a fundamental misunderstanding about 'resolution' in digital audio.

You don't 'lose resolution' by moving away from 0 dB FS ('digital zero'). You simply move your signal closer to the digital noise floor.

Since the that noise floor with 24 bit digital sample word lengths is around 140 dB below 0 dB FS and the analog components in your chain certainly have a much higher noise floor (probably more like in the range of 80-110 dB S/N for your chain even with optimal gainstaging), you shouldn't have to worry about dipping significant signal into the digital noise floor -- even if you stay a very comfortable 18 to 12 dB under 0 dB FS.

Since the problem you sought to address by using Dolby isn't really a problem, my thoughts on various Dolby NR schemes are probably irrelevant, but I will say this: there seems little point in using such systems, which have their own negatives and tradeoffs, if you don't *need* to. And, with regard to your concerns above, you don't.

With regard to using Dolby as an 'effect' -- well, what the heck, go ahead and experiment, you might find you like it. Anything is possible.

OK, thanks, but I'm not clear on why you don't lose resolution at lower signal levels. If there is info on the Web that explains this, please point me there and I will do my homework.

I can see where you don't lose any sample-rate resolution. My understanding, or mis-understanding applies to amplitude vs number of bits to represent a waveform at a given amplitude.

The misunderstanding may arise from encoding techniques, pre-emphasis, or signal processing that I may not be aware of, but nothing in the past when I researched A/D conversion for hi-fi audio jumped out at me compared to basic A/D conversion as it was in the beginning with, say digital telephony in the '60s, digital oscilloscopes, or even digitizing DC signals for measurement, like a DMM or industrial PLC.

In the most basic digitizing scheme, I will take a sine wave for example.

Assume the following:

* An 8-bit converter, for simplicity's sake, with 256 discrete levels represented by the range of numbers 0 to 255.

* A "zero-signal" bias level of 127, allowing both positive and negative sides of the incoming signal to be digitized.

If the incoming level is digitized to the maximum level before digital clipping, assumed 0 dB here, then there will be 127 discrete steps below zero and 127 discrete steps above zero representing the entire amplitude of the waveform. This works out to 254 non-zero discrete levels, plus one discrete level representing the zero-signal bias level, which adds up to 255 discrete steps overall.

Now take the extreme case where the incoming signal level is so low that the discrete steps representing the entire sine wave from top to bottom are one step above zero and one step below zero. This is where I assume we have lost resolution, since we now only have 3 discrete levels representing the sine wave; zero (127), minus one (126) and plus one (128). The resulting un-filtered wave is now basically a square wave.

In theory, yes, it's possible to filter the square wave to make it into a sine wave, but if the sampling rate is 44.1 KHz, and the waveform recorded is at 20 Hz, the result still won't be a sine wave, considering the filtering takes effect at frequencies above 20 KHz on a typical D/A converter.

Now, if all of this is moot due to encoding techniques or other forms of DSP in use across the broad range of conversion techniques (PCM, 1-bit, oversampling, etc) then I am not aware of how an incoming signal that is so low that it has 3 discrete steps would not have a loss in resolution compared to the maximum signal level that is represented by 255 discrete levels.

So that's how I'm basing my theory of lost resolution as signal levels are reduced below 0 dB, full-scale, max signal before digital clipping. I am open to being educated here if I am totally off track.