Question about Digital(ADC)

[ncdrawl]

so tell me your thoughts..

Why are modern A/D converters unable to accurately reproduce an analog recording? - Gearslutz.com

[SoNic_real_one]

That's next to "Why are the vintage analog devices unable to accurately record or reproduce an analog signal?"...
I guess because of the Third Law Of Thermodynamic?

That's a bunch of bull... A modern top-of-the line A/D converter can surpass the human hearing performance. Or noise and distortion of an analog magnetic medium.

[wakibaki]

No way are we going back to analog tape sound recording. No way are we going back to vinyl disks. No way are we going back to analog TV. No way are we going back to the widespread use of valves. AM radio is going to die out. FM radio is going to die out.

Stop gazing wistfully back into the past and realise that the large majority of the human race don't want analog stuff any more and those who do are just old folks who are going to die out eventually.

w

[fzaad]

I think better question would be why old folks wannabe hifiers like distortions?

[abraxalito]

Originally Posted by ncdrawl

so tell me your thoughts..

Its a really interesting question. I haven't trawled through the 1k+ posts on that thread, significant though to note no-one I've seen has come up with a convincing answer and most seem to either misunderstand the question or misunderstand digital audio (or both).

Myself I would say its most likely to be a system implementation issue. The OP does not say exactly what his set-up is - he's quite possibly getting RF contamination into his ADC or DAC/amps.

[jcx]

skimming some of the thread I believe he refers to "prosumer" pc sound card - not true pro grade studio rack converters - not that the same few manufacturer's flagship monlithic ADC chips aren't used in both

[Diginerd]

The answer is actually pretty easy.

Because you're passing through some active electronics in front of the ADC, and no matter what you do they will change things infinitely more than a length of copper. Nothing wrong with digital recording, but just like everything it's hard to do well. Particularly when the issues they're discussing are really centered around the analog side of the ADC (assuming 24 bit/44.1 recording with a decent clock).

In this case it sounds like folks are getting confused between "a million perfect copies" AFTER something has been digitized, and understanding that AD/DA excellent converter design is both a black art AND a science. Something it shares with quantum mechanics.

In both cases the Math is far beyond reproach, but folks don't like the answers. If anyone doesn't believe that Nyquist Theorem is correct then they shouldn't hear anything from a digital system. nyquist math doesn't exist because of digital recording, it's the other way around. digital recording is rooted in Nyquist, without it there can be no digital recording.

In my humble opinion, most of these debates turn into a train wreck because musicians usually didn't do that well in Maths and Physics in school and didn't bother taking deductive reasoning either. Digital audio is convenient and powerful, but the basic math behind it scares folks. That's a problem, as knowing at least the basics is vital to avoid making messed up recordings.

No problem though, because Product Y has a gajillion more bits and samples at 2GHz, to it must be better for recording than that Prism ADC running at 24 bits and 44.1KHz.

oRLY?

The counter question should be along the lines of: how come when I record the output of my DAW to tape does it sound different?!

Seriously, debates like the one linked to over at GearSlutz are the reason I gave up frequenting "Pro Audio" boards. Crap, sorry guys, just realized I've been on a rant..



Rob

[abraxalito]

Originally Posted by Diginerd

The answer is actually pretty easy.

Join up to GearSlutz then and sort them all out

Because you're passing through some active electronics in front of the ADC, and no matter what you do they will change things infinitely more than a length of copper. Nothing wrong with digital in theory, but just like everything it's hard to do well.

Hard to explain why changing things 'infinitely more than a length of copper' should be totally inaudible in some cases but not in this case. Your 'pretty easy' answer doesn't make sense to me yet...

[abraxalito]

Originally Posted by jcx

skimming some of the thread I believe he refers to "prosumer" pc sound card - not true pro grade studio rack converters..

I've got a bit further down the thread - the box he's using is this one:

Mytek 8X192

Definitely looks like a pro-grade rack mount converter.

[jcx]

the gearslutz thread starts off wrong with old "analog has infinite resolution" canard - try looking up Shannon-Hartley "Channel Capacity Theorem" Shannon?Hartley theorem - Wikipedia, the free encyclopedia

add a couple of data points such as the last US manufactured analog master tape was speced at 85 dB S/N with "0 dB" being the recording level that gave 3% 3rd harmonic distortion from saturation

or that "extended analog bandwidth" only came in later years with narrow gap custom tape heads and servo tracks for precise head alignment and still requires non-standard high tape speed and wasn't typical practice during analog tape audio mastering's heyday - substantial roll off starting below 20 KHz wasn't uncommon (and look up "low end head bump" for the problems at the other frequency extreme)

or that analog tape has scrape/flutter audio frequency "FM" distortion - Plangent Processes

there is little question that current 192k/24 bit ADC with 120 dB S/N and distortion below -110 dB is more accurate than any 70's audio studio's analog recordings


[edit] the box does look adequate although from the website it appears that it uses at least 5 yr old parts - a lifetime in modern semiconductor innovation rate