barnacle bill

32 bit music

36 posts in this topic

So do i, but it would be nice to listen to this material if was available hence the question.

I agree, and if only someone would sell me high quality 24 bit 96k or 192k recordings at reasonable prices (i.e. much the same or less than current CDs), then I have my credit card ready and waiting. But worrying about 32 bit recordings is pointless. Computers work natively with 32 bits and a lot of the time it is just as easy to deal with 32 bits quantities as it is with 24 bit quantities, but our ears can't cope with the dynamic ranges beyond those encoded with 24 bit depths, and that is all there is to it.

0

Share this post


Link to post
Share on other sites
Which ones?

Mostly the second law. It is all tied up with thermal noise and information entropy.

I have done some quick calculations. Assuming an amplifier input with 2V sensitivity into 50K Ohms running at room temperature:

32 bits at 6db/bit is a dynamic range of around 216dB. At full scale (32-bits), the amplifier input current is around 40uA. The current for 1 bit output is 9.3E-15A.

I calculate the Johnson noise current alone at 300K as 8.14E-11A, making just this noise current around 8,700 times greater than the signal.

To make use of 32-bit resolution, you would need to cool the whole of your audio system and your ears to below the temperature of liquid helium.

Don't try this at home!

1

Share this post


Link to post
Share on other sites

Let's not forget that the top full-range speakers (f. ex. B&W 800, ATC SCM300) have a specified maximum continuous SPL of around 120dB at 1 meter and most rooms have a noise floor of around 30dB.

This means that with such speakers the useable dynamic range is below 90dB and that more ordinary loudspeakers will reduce this DR to values of 75-80dB (13bit).

R

0

Share this post


Link to post
Share on other sites
Mostly the second law. It is all tied up with thermal noise and information entropy.

I have done some quick calculations. Assuming an amplifier input with 2V sensitivity into 50K Ohms running at room temperature:

32 bits at 6db/bit is a dynamic range of around 216dB. At full scale (32-bits), the amplifier input current is around 40uA. The current for 1 bit output is 9.3E-15A.

I calculate the Johnson noise current alone at 300K as 8.14E-11A, making just this noise current around 8,700 times greater than the signal.

To make use of 32-bit resolution, you would need to cool the whole of your audio system and your ears to below the temperature of liquid helium.

Don't try this at home!

Dusted then...:D

0

Share this post


Link to post
Share on other sites
Dusted then...:D

In practical terms, yes. A well designed sixteen-bit system will be sonically indistinguishable from a well designed system with a larger word size. Even with a 24-bit system, the lowest four to six bits will most likely just be noise. Going to 32 bits is just silly.

The distortion produced by even the best loudspeakers is still orders of magnitude greater than that produced by a well designed sixteen-bit DAC.

0

Share this post


Link to post
Share on other sites
Mostly the second law. It is all tied up with thermal noise and information entropy.

I have done some quick calculations. Assuming an amplifier input with 2V sensitivity into 50K Ohms running at room temperature:

32 bits at 6db/bit is a dynamic range of around 216dB. At full scale (32-bits), the amplifier input current is around 40uA. The current for 1 bit output is 9.3E-15A.

I calculate the Johnson noise current alone at 300K as 8.14E-11A, making just this noise current around 8,700 times greater than the signal.

To make use of 32-bit resolution, you would need to cool the whole of your audio system and your ears to below the temperature of liquid helium.

Don't try this at home!

not wishing to be arsey, but 32*6=192.

This makes me wary of the rest of your calculations. But it seems to be widely accepted that thermal noise in a dac is around -120 dB yielding 20 bits of effective snr. 24 bits is therefore excessive.

0

Share this post


Link to post
Share on other sites
not wishing to be arsey, but 32*6=192.

This makes me wary of the rest of your calculations. But it seems to be widely accepted that thermal noise in a dac is around -120 dB yielding 20 bits of effective snr. 24 bits is therefore excessive.

Quite right. I must have had a thinkahead buffering problem in my brain and calculated 36*6. Apologies for the mistake.

0

Share this post


Link to post
Share on other sites
Quite right. I must have had a thinkahead buffering problem in my brain and calculated 36*6. Apologies for the mistake.

What would the new calcs be, still liquid helium cool?

0

Share this post


Link to post
Share on other sites
Quite right. I must have had a thinkahead buffering problem in my brain and calculated 36*6. Apologies for the mistake.

No worries, I shouldn't really have mentioned it, but was overcome with a pedantic urge. As a matter of interest do your figures agree with the -120db figure I have seen?

0

Share this post


Link to post
Share on other sites

There are DAC chips, such as the Sabre 9018 (used by Weiss, W4S, etc) that have a quoted DR of 135dB. This will inevitably drop off to some degree when an output stage is applied, but in a good design can still be in the region of 128dB or so. IMHO this is way beyond audibility.

The Sabre chip also has 32 bit playback, however the main reasoning for this is not to allow input of 32 bit source files, but for signal processing (ie up-sampling / volume control) with minimal impact on SQ.

0

Share this post


Link to post
Share on other sites
There are DAC chips, such as the Sabre 9018 (used by Weiss, W4S, etc) that have a quoted DR of 135dB. This will inevitably drop off to some degree when an output stage is applied, but in a good design can still be in the region of 128dB or so. IMHO this is way beyond audibility.

It's also beyond playbackability...at least with any of the domestic sound reproduction speakers that I've heard of, even for enourmous mamoths such as these:

B-W808.JPG

jbl4350studiomonitors.jpg

Ric

0

Share this post


Link to post
Share on other sites

32 bit is commonly used in DAW workstations for heavy processing(32 bit floating point actually) and there are some advantages for that...but for playback? no.

0

Share this post


Link to post
Share on other sites
It's also beyond playbackability...at least with any of the domestic sound reproduction speakers that I've heard of, even for enourmous mamoths such as these:

B-W808.JPG

jbl4350studiomonitors.jpg

Ric

what are those blue ones?

0

Share this post


Link to post
Share on other sites
good design can still be in the region of 128dB or so. IMHO this is way beyond audibility.

With DACs, perhaps. As for ADCs: the best I've measured so far in real-world situations manage 108-110dB, unweighted, 20kHz band.

The Sabre chip also has 32 bit playback, however the main reasoning for this is not to allow input of 32 bit source files, but for signal processing (ie up-sampling / volume control) with minimal impact on SQ.

Even that is stretching it a bit (pun intended), and I am nearly confident that the very same chip architecture reduced to 24 bit would yield the same performance.

There is, however, a tiny shred of justification in the scenario where a signal processor preceeds the DAC chip. In such case it would be a shame (at least theoretically) to reduce the processor output to 24 bits, only to carry it over to the DAC's oversampling filter where internal word size is expanded to 48 bits or whatever. Might as well then throw 32 bit over the interface... it would give the chip and system designers a warm and fuzzy feeling.

0

Share this post


Link to post
Share on other sites

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

  • Recently Browsing   0 members

    No registered users viewing this page.