Jump to content
IGNORED

Which DACs bypass digital filtering?


Recommended Posts

16 minutes ago, mansr said:

It is possible in some DACs (though probably not that one), with lots of averaging, to recover linearity down to the 24th bit. The usable dynamic range isn't anywhere close to that, of course. And don't get me started on "the non-oversampling principle."

The useful dynamic range is probably 20 bits or less. I think the best ever measured was 21 bits but I can't remember which DAC that was. It is very hard to get much better than 20 bits just because of the inherent noise of moving electrons around.

Link to comment
21 minutes ago, Jud said:

 

I have a quiet listening room in an exurban setting (about 3 miles from the nearest town of 5000) in a very well insulated house (we lost power and thus heat for 24 hours in a winter windstorm with 50-60mph winds and temperatures below freezing; indoor temperatures dropped from their setpoints of 69-70 degrees F to 67-68 degrees). The background level is about 30dB.

That sounds about right. I have measured mine as low as 30bB but most of the time it is in the low to mid 30 range. I don't think most appreciate that any sound that our brains can process (including music) must first emerge from that background din (noise). I read some interesting research that showed that our brains don't do well in a really quiet environment. They put people in an anechoic chamber and if memory serves they started having hallucinations after a while. Link below:

https://www.smithsonianmag.com/smart-news/earths-quietest-place-will-drive-you-crazy-in-45-minutes-180948160/

 

My point being that an extreme dynamic range is not really very useful and is rarely if ever used to its full capacity. The low end is lost and the high end would be dangerous. That said, most recordings especially "loudness wars" recordings are so compressed that they use only a fraction of what would be pleasing, safe and easily available. 

Link to comment
56 minutes ago, mansr said:

This is another variant of the same confusion. The total noise power of TPDF dither at the 16-bit level is roughly -92 dB. The spectral density, however, is around -135 dB/Hz. If we create a 1 kHz tone at -100 dBFS and dither it to 16-bit precision, we get this spectrum:

image.thumb.png.92cdf4d065dce9e1e2e235055f7bc1e9.png

 

The tone is clearly visible above the noise. If we play this signal on a decent DAC with the volume turned up high, we can hear a distinct tone as well as some hiss. This is because the tone has much higher intensity than the noise in the immediately surrounding frequencies. The ear separates sounds by frequency much like an FFT, so it's no surprise it too can detect such signals.

 

When people talk about hearing below or into the noise, this is what they (perhaps unknowingly) mean. There is nothing special, mysterious, magical, or in any way remarkable about it.

 

Dither is just noise with a specific purpose. In the context of this discussion, it requires no special consideration.

Thanks, I stand corrected. I guess I knew that one can hear below the ambient noise but I did not express what I was trying to get across clearly. I remember something I read years ago said that for something to reach the level of perception below the noise floor it had to be differentiated from the noise for the brain to register it otherwise it would be ignored as noise. This requires more brain processing than sound above the noise floor. This fits in with your explanation above.  Thanks again.

Link to comment

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now



×
×
  • Create New...