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Old 25th August 2012, 10:59 PM   #26981
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I first worked with PCM audio in 1970 for US Army telephone systems (mountaintop to mountaintop). No dither and nobody'd ever heard of it.

When CD first came out, we had the Kyocera, the first generation Philips-based players, the Yamaha CD-X1 (I think...) at the retail store where I was, and I bitched as much as anybody about the sound.

But that was then, this is now. If folks only complain but don't do anything nothing improves.

WRT John's scepticism, let me just say that the mathematical result of an ideal bandlimited, properly dithered A/D/A conversion is a exact replica (in all respects, at all levels including below the smallest bit, and at all frequencies - exact) of the original, plus a small noise, plus a time delay. Period. That's the ideal.

To make progress in this field we need to keep in mind that observed imperfections are not fundamental to the A/D/A conversion, but are instead artifacts of a particular implementation.
Maybe it will take a Blowtorch quality implementation to make the most discerning happy, but that shouldn't be much of a surprise considering the difficulty of the task.

Thanks, as always,
Chris

Last edited by Chris Hornbeck; 25th August 2012 at 11:01 PM.
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Old 25th August 2012, 11:09 PM   #26982
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Quote:
Originally Posted by Chris Hornbeck View Post
To make progress in this field we need to keep in mind that observed imperfections are not fundamental to the A/D/A conversion, but are instead artifacts of a particular implementation.
Yes, but some A/D/A conversions are easier to implement of higher quality than others. Like, using some components and topologies is easier to implement higher quality power or mic amps.
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Old 25th August 2012, 11:37 PM   #26983
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I'm quoting textbooks from forever. Here's one:

Textbook of Hearing Aid Amplification - Robert E. Sandlin - Google Books

Thanks,
Chris
? The text you quoted gave 5-10 db for the headroom and gave levels higher than I measured.

Having done live symphony reinforcement is where my preferred 20-30 db comes from. The text mentions comparing the levels on an oscilloscope. That most likely would have been done with a recording.
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Old 25th August 2012, 11:51 PM   #26984
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There's nothing special about the noise in a dithered A/D/A conversion that would interfere with the ability to hear below broadband. And a properly dithered conversion *completely* maintains all information below the noise floor. What's the point here?

Thanks,
Chris
Again we are basically in agreement! You can hear signal below the noise level in both real and digital systems. Where we differ is in what the noise level is. When you measure acoustic noise there should be an "A" weight filter in use. The noise from a DSP system is not specified that way. Good practice would be to record the signal with the record system noise floor below the signal noise floor.
The text you showed reported 104 in the 7th row of the balcony in an NC20 space. That would put the front row about 125 peak with a noise floor of 15 db above 3K.

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Old 25th August 2012, 11:53 PM   #26985
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? The text you quoted gave 5-10 db for the headroom and gave levels higher than I measured.

Having done live symphony reinforcement is where my preferred 20-30 db comes from. The text mentions comparing the levels on an oscilloscope. That most likely would have been done with a recording.
The 105dB SPL of an audience seat for an orchestral performance is stated as an "instantaneous peak". For recording, headroom above this is of course required, for all the usual reasons. But we're discussing storage, where no (or 1/2 dB or so) headroom is required.

(Nobody would suggest recording at 16 bits these days, although it can be done perfectly well and with an effectively electronic noise free background when making live recordings. Audiences are loud too. But that's a completely separate discussion.)

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Chris
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Old 25th August 2012, 11:56 PM   #26986
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The text you showed reported 104 in the 7th row of the balcony in an NC20 space. That would put the front row about 125 peak with a noise floor of 15 db above 3K.
That requires a rather sweeping generalization from free air conditions to concert hall conditions. Not at all certain that I can buy it.

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Chris
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Old 26th August 2012, 12:05 AM   #26987
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The text gave 104A SLM reading! That's loud. We agree recording needs to be done with more than 16 bits.

Where we disagree is that there actually are some situations where more is required for reproduction. Of course since virtually all the recording gear is advertised as 24 bit, it would be nice to have the storage method to match

Just for grins a Shute Beta58 microphone produces 2.6 mV at 94 db and is rated at 150 ohms. What is the S/N from a recording studio noise floor to a heavy metal singer with lips on the windscreen?
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Old 26th August 2012, 12:09 AM   #26988
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That requires a rather sweeping generalization from free air conditions to concert hall conditions. Not at all certain that I can buy it.

Thanks,
Chris
The hall is a well known space is where the NC numbers come from. The curve loss is from memory.
The 10db path gain is from critical distance and the other 10 is SLM-peak.
Then there is the story of the concert hall that put in two 4" conduits to allow for recording. It destroyed the NC rating!

Last edited by simon7000; 26th August 2012 at 12:12 AM.
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Old 26th August 2012, 12:16 AM   #26989
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Just for grins a Shute Beta58 microphone produces 2.6 mV at 94 db and is rated at 150 ohms. What is the S/N from a recording studio noise floor to a heavy metal singer with lips on the windscreen?
When they get through "mastering" it? Maybe 10dB - it'd be funny if it weren't so true these days. I can't disagree that a "24 bit" format would be plenty good enough for everybody, and the CD sampling rate is really not wonderful, but I'm worried that the attention of folks in a position to move things along could easily be distracted from the terrible state of so much professional mastering these days while chasing tiny marginalia.

Listen to any of the 2008 Van Morrison reissues and tell me that even 8 bits is needed anymore. Or recent EmmyLou Harris remasters, or lots of others. Sinful.

Thanks, as always,
Chris
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Old 26th August 2012, 12:23 AM   #26990
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Chris, Chris, Chris,

Just because you are correct and understand the technical details doesn't mean you are right on this thread! Here it is done by mob rule.
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