Topic: Analog to 24bit question

[Roving Sign]

Another interjection:

If I follow the dmccabe logic - shouldnt we all be remastering our old 16 bit DATs at 24 bits - just like the cassette process? If 24 bits makes cassettes sound better, why not 16 bit DATs???

I think many people are indeed doing just this

I know that's what I plan on doing

When it comes to preservation and archiving - shouldn't you be trying to keep the exact digital info as it is on the DAT?

Once that is done - everything else (including any sound enhancing tricks)- is infinitely repeatable...

[Brian Skalinder]

no, because the DAT 16-bit was already dithered...

Doesn't this assume all 16-bit ADCs (whether internal to the DAT recorder, or external) employ on-board dither?  Maybe they do, I dunno.  If not, then seems the answer should really be "it depends on whether the 16-bit ADC employed on-board dither".

[Roving Sign]

If I follow the dmccabe logic - shouldnt we all be remastering our old 16 bit DATs at 24 bits - just like the cassette process? If 24 bits makes cassettes sound better, why not 16 bit DATs???

If making edits to 16-bit masters after transferring to computer, then yes - you should do so with software that uses internal precision of 24-bit, or better yet 32bfp.  In this case, we're talking about the precision used in manipulation of the digital signal within the digital realm, not the transfer of an analog signal into the digital realm.  Different beast entirely.

There's no point in transferring a 16-bit DAT to PC at 24-bit, since it's all within the digital realm (DAT > bit-transparent S/PDIF > PC).  The least significant bits would simply be padded with zeroes. 

Understood.

I suppose one could transfer into the analog realm and then back (DAT > DAC > ADC > PC), but...not sure what the point would be,

Thats more what I am talking about - the fact the analog signal is from a 16 bit DAT seems irrelevant following the mccabe logic...be it from a cassette or a DAT, its still an analog signal...

[dmccabe]

When it comes to preservation and archiving - shouldn't you be trying to keep the exact digital info as it is on the DAT?

Once that is done - everything else (including any sound enhancing tricks)- is infinitely repeatable...

It all depends, there is no definite rule for every recording... is it a DAT master... or an analog recording transferred to DAT - big difference. looking back now, DAT has turned out to be a shitty format. It compressed all the dynamic range of the mic info down to 16-bits, and you can't change that. I'll take an analog master over a DAT master any day. The only benefit we all got from DAT was less tape hiss and the ability to make a digital copy.

BTW, Micheal Grace is a contributing member of MOTB and has donated quite a few pieces of hardware to our project. We also have custom modded V3's done by Mike for using the analog inputs for line in rather than mic in (impedance matching mods). We use V2s and V3s as our preamp front end out of our Technics reels.

If you have a DAT master that is a good show you want to edit... you want to do all those edits in 24-bit. So the best way to get it there is out through a good DAC, like the Benchmark DAC-1. If you use a shitty DAC, then you might as well upsample the 16/48 DAT for a better result. You need a good DAC to get it back to analog.

If anyone needs some audio files transferred for a listening test... we have lots of hardware and can post the samples.

Personally I really love the Korg DSD stuff more than the higher end A/Ds...

Also I have quite a few live shows where I used KM184 > V3 > digital out to 24/96 Marantz 671 and at the same time out of the V3 analog out > Korg MR-1000 DSD. Then you can compare the Audiogate 24/96 to the V3 24/96. I like the Korg much better.

[Gutbucket]

Lots of posts wile I was typing.. here it is anyway..

Sorry to interrupt - just curious here....

Which would you prefer for 16 bit listening?

A) 24 bit master > dithered to 16 bits

B) Native 16 bit samples

I would tend to favor "B" - theoretically...

With the little knowledge that I have I would prefer 24 > 16 with dither.  I say this because the capture and any post processing[/] would be done in 24 bit where there is less loss from this work, I believe.  I always record 24/48 and do post in 24/48 for this reason.  When I am done I mix down and dither to 16/44.1.

If it is just captured at 24 and then dithered down to 16 I do not see what benefit there can be.  It can never sound better than the original.  As has been posted earlier, it can sound different, but only with tweaking.  If I am wrong someone please tell me how the copy can sound better than the original.  Can a 24 bit copy sound better than a 16 bit copy?  I do not know.  Some think so.  But I would not put a lot of credence in that myself until it had been tested many times in double-blind tests.  As usual, YMMV.   

Happy Trails.

No, you both are missing the point.  The dithered 16bit signal doesn't sound better than the 24bit one.  Information is lost durring that transformation of course. But the resulting 16bit signal, after being dithered from 24bits is better than one originally recording at 16bits.  There is more information there because of the dithering process.

Keep in mind that processing can be done at a higher bit rate than the origional file, so future processing is not the concern, it's capturing extra information at the inital A>D stage in hte original recording.  

Tim is spot on with the comment on the A/D's that sample at 20 or 24bits and imediately dither down to a 16bits for recording to DAT or any other 16bit format.  It 'crams' more information in the 16bit file by sampling at 24bits and dithering than it would get by sampling at 16bits.

Another interjection:

If I follow the dmccabe logic - shouldnt we all be remastering our old 16 bit DATs at 24 bits - just like the cassette process? If 24 bits makes cassettes sound better, why not 16 bit DATs???

Good question.  I think the answer is that the 16bit tapes have already gone through the inital A/D stage when they were recorded, so any information beyond 16 bits is already lost.  Analog tapes have not been sampled yet and so can benefit from a better inital A/D conversion. Just a guess.

Here's another good article on dither from the Rane website. (Here's the same as a PDF). One thing mentioned inb it that I found interesting and I think applies to this topic (bold is my emphasis)-

Here is what is gained by using 20-bits:

• 24 dB more dynamic range
• 24 dB less residual noise
• 16:1 reduction in quantization error
• Improved jitter (timing stability) performance

And if it is 24-bits, add another 24 dB to each of the above and make it a 256:1 reduction in quantizing error, with essentially zero jitter!

As stated in the beginning of this note, with today's technology, analog-to-digital-to-analog conversion is the element defining the sound of a piece of equipment, and if it's not done perfectly then everything that follows is compromised.

With 20-bit high-resolution conversion, low signal-level detail is preserved. The improvement in fine detail shows up most noticeably by reducing the quantization errors of low-level signals. Under certain conditions, these course data steps can create audio passband harmonics not related to the input signal. Audibility of this quantizing noise is much higher than in normal analog distortion, and is also known as granulation noise. 20-bits virtually eliminates granulation noise. Commonly heard examples are musical fades, like reverb tails and cymbal decay. With only 16-bits to work with, they don't so much fade, as collapse in noisy chunks.

Where it really matters most is in measuring very small things. It doesn't make much difference when measuring big things. If your ruler measures in whole inch increments and you are measuring something 10 feet long, the most you can be off is 1/2 inch. Not a big deal. However, if what you're measuring is less than an inch, and your error can be as much as 1/2 inch, well, now you've got an accuracy problem. This is exactly the problem in digitizing small audio signals. Graduating our audio digital ruler finer and finer means we can accurately resolve smaller and smaller signal levels, allowing us to capture the musical details. Getting the exact right answer does result in better reproduction of music.

[/list]

[dmccabe]

I think the answer is that the 16bit tapes have already gone through the inital A/D stage when they were recorded, so any information beyond 16 bits is already lost.  Analog tapes have not been sampled yet and so can benefit from a better inital A/D conversion. Just a guess.

Exactly.

[Petrus]

You can't have sound without bit rate (dynamic range) AND frequency response. This is SO BASIC, I am still amazing you are continuing to post like you actually have experience in transferring analog cassettes to digital. Dynamic range IS DIFFERENT than frequency response, but they are directly related to each other. The fidelity of frequency response is also directly related to the quality of the bit converter. A sine curve at 24/96 has more detail than a sine curve at 16/44.1 -- even when the dynamic range is the same!

-----------------

When you bring up the Nyquist theorem, it shows that you are trying to make your argument based on the mathematical limitations of dynamic range. Are you also saying that all A/D's running at the same bit rate and frequency sound the same?
Are you saying that any A/D sounds the same at 16-bit and 24-bit?

If the sine wave is within the frequency range that the digital system can handle (less than half of sample rate), then it is perfect on both 16 and 24 bit systems. Basic fact of digital recording. That's why we have low-pass filters after the D/A converter to smooth the signal...

Nyquist theorem has nothing to do with dynamic range, only with maximum frequency range of a given digital system. Basically the sample rate has to be twice the highest frequency recorded.

Dynamic range and frequency range are not connected in any way. Bit rate dictates the DR, sample rate only the maximum recordable frequency.

You have your bitrate/samplereate wires crossed somewhere, dmccabe, sorry.

[Gutbucket]

...
As for going to 16-bit from a 24-bit source.

Most top mastering engineers (I am not going to drop a name here, but think the entire Hendrix remastered catalog) take their 24/192 digital masters and send them back out to analog... then back into 16-bit/44.1 A/D of their choice for Cd master... rather than dither them in software
....
If you have a DAT master that is a good show you want to edit... you want to do all those edits in 24-bit. So the best way to get it there is out through a good DAC, like the Benchmark DAC-1. If you use a shitty DAC, then you might as well upsample the 16/48 DAT for a better result. You need a good DAC to get it back to analog.
...

Interesting, thanks.  I suppose conversion is an area where the digital schemes can still use plenty of improvement to compete with quality hardware when going either direction.

[Roving Sign]

I think the answer is that the 16bit tapes have already gone through the inital A/D stage when they were recorded, so any information beyond 16 bits is already lost.  Analog tapes have not been sampled yet and so can benefit from a better inital A/D conversion. Just a guess.

Exactly.

Both are analog signals - so because one was derived from a DAT, it cant benefit from your process?

It would seem to me that both should benefit...

furthermore - the above seems in conflict with:

you want to do all those edits in 24-bit. So the best way to get it there is out through a good DAC, like the Benchmark DAC-1. If you use a shitty DAC, then you might as well upsample the 16/48 DAT for a better result. You need a good DAC to get it back to analog.

[Brian Skalinder]

And one step futher, but much more contemporary, is the Grace ANSR.
Were you running it, or no?
Do you want to further change that?

Interesting thought.  I ran ANSR, quite a bit.  I generally didn't edit those recordings in post, but I did on a few occasions.  For some reason I thought ANSR is different from traditional dither, though I couldn't tell you why. 

I think the answer is that the 16bit tapes have already gone through the inital A/D stage when they were recorded, so any information beyond 16 bits is already lost.  Analog tapes have not been sampled yet and so can benefit from a better inital A/D conversion. Just a guess.

Exactly.

I'm struggling to reconcile the above with...

If you have a DAT master that is a good show you want to edit... you want to do all those edits in 24-bit. So the best way to get it there is out through a good DAC...

So if information beyond the original 16-bits is already lost, why transfer 16-bit DAT > DAC > ADC > 24-bit?  If the additional information is already lost, converting to analog and then back to digital doesn't re-gain any of the lost information.

And if the point of converting back to analog (as has been suggested) is to avoid dithering twice (dither once when capturing the original 16-bit capture, then dithered again after editing)...isn't the dither noise in the 16-bit recording simply passing into the analog realm, then back into digital, i.e. doesn't the dither noise remain in the signal, so you're experiencing the effects of double-dithering regardless?

Additionally, if one's editing software uses 32bfp internal precision, then wouldn't going 16-bit > DAC > ADC > 24-bit still require two dither stages?  Once to capture the 24-bit recording, and again dithering from 32bfp to one's target bit depth?  So really, if we assume converting into the analog realm and then back to digital, is, in fact, better, shouldn't we go 16-bit > DAC > ADC > 32 bfp (or at whatever bit-depth our editing software uses internally)?

If the answer to going back into the analog realm is to leverage the sonic characteristics of the intermediate analog gear, that's one thing.  But if it's to avoid double-dither, or some other issue, I'm still not grasping why it's better.

[dmccabe]

If the sine wave is within the frequency range that the digital system can handle (less than half of sample rate), then it is perfect on both 16 and 24 bit systems. Basic fact of digital recording.

There is no such thing as a perfect digital reproduction from an analog signal!

You have your bitrate/samplereate wires crossed somewhere, dmccabe, sorry.

The topic is analog to digital...
The example was an analog "sine wave" converted it to digital... Mr. Nyquest.
It's always the guys who don't actually master audio that bring up the Nyquest Theory that they just Google'd...

Do you agree that different A/Ds have different sounds? Some are more transparent than others, some have a warmer coloration. OK... but they are both at 16/44.1, how do you account for the fact that they sound different.

Do you have the hardware to play back a 24-bit file? There are plenty of MOTB releases done at 24-bit and 16-bit -- both from the same analog source. Go see if you can hear the difference?

[Roving Sign]

You have your bitrate/samplereate wires crossed somewhere, dmccabe, sorry.

The topic is analog to digital...
The example was an analog "sine wave" converted it to digital... Mr. Nyquest.
It's always the guys who don't actually master audio that bring up the Nyquest Theory that they just Google'd...

Do you have the hardware to play back a 24-bit file? There are plenty of MOTB releases done at 24-bit and 16-bit -- both from the same analog source. Go see if you can hear the difference?

Sorry for the topic sway - just trying to see if we arrive at the same conclusion from a different angle.

Im sure there are differences - however we dont seem sure what to attribute those differences to. You are pointing to a factor that we all dont agree on...

And..lighten up a little dude - you sound FAR from authoritative.

[dmccabe]

I'm struggling to reconcile the above with...

If you have a DAT master that is a good show you want to edit... you want to do all those edits in 24-bit. So the best way to get it there is out through a good DAC...

So if information beyond the original 16-bits is already lost, why transfer 16-bit DAT > DAC > ADC > 24-bit?  If the additional information is already lost, converting to analog and then back to digital doesn't re-gain any of the lost information.

no additional gain of info, the transfer to 24-bit from DAT is assuming you have additional edits to do... pitch change, cross fades, patches. You would not want to make any of those type of changes to a 16/48 file, you would hear digital artifacts from those types of changes. You would "hear them less" when done in 24/96 -- them sampled back down to 16/44.1

It's all about doing the least amount of destructive artifacts. You don't "gain" any quality. You just don't gain as much artifacts.

[dmccabe]

And..lighten up a little dude - you sound FAR from authoritative.

I don't pretend to be  the authoratative voice on the subject... but when some one makes a statement like:
"But like I said, 24 bits only makes files larger", then bullshit needs to be clarified.

If you have any audio samples you would like to post to show your point of view, feel free to include links.
There are over 50 shows with links to find them as examples over at www.motb.org.

Transferring analog sources is what the MOTB project is all about... and since we have some actual PRO AUDIO ENGINEERS in the group, maybe you should take some time listening.

[Roving Sign]

Care to refer us to any sources?

What should we listen for?