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Author Topic: AD-122 "Soft Saturation" Question for Mr. Lavry  (Read 7307 times)

mark4man

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AD-122 "Soft Saturation" Question for Mr. Lavry
« on: September 27, 2006, 01:45:48 PM »

Dan...

The soft saturation function on the AD-122...

...is this similar to "Type IV Conversion" offered up by dbx in a few of their mastering processors? (most notably the Quantum II)...

(ftp://ftp.dbxpro.com/pub/PDFs/WhitePapers/Type%20IV.pdf)

...whereby the top 4db under unity is logarithmically mapped as an "overload region", expanding the dynamic range there by increasing the # of bits that represent the signal.  They claim that the high fr.'s are retained as a result of this process, as they are not w/ analog (or typical "look-ahead, brick wall" digital) limiting.  (everything below 4dB remains linear.)  They also say that the converter cannot be clipped as a result.

Are functions such as these (yours & dbx's) implemented within the A/D itself by means of a digital algorithm...or pre-staged?  I remember reading somewhere (maybe Brad's forum) where you said that this can be accomplished in both the hardware & software worlds; and was wondering if; with some of the better plug-in limiters on the market...where they offer so-called "soft clipping", if that is in any way similar to yours (or anywhere near as effective)?

Thanks,

mark4man
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danlavry

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Re: AD-122 "Soft Saturation" Question for Mr. Lavry
« Reply #1 on: September 27, 2006, 03:01:41 PM »

mark4man wrote on Wed, 27 September 2006 18:45

Dan...

The soft saturation function on the AD-122...

...is this similar to "Type IV Conversion" offered up by dbx in a few of their mastering processors? (most notably the Quantum II)...

(ftp://ftp.dbxpro.com/pub/PDFs/WhitePapers/Type%20IV.pdf)

...whereby the top 4db under unity is logarithmically mapped as an "overload region", expanding the dynamic range there by increasing the # of bits that represent the signal.  They claim that the high fr.'s are retained as a result of this process, as they are not w/ analog (or typical "look-ahead, brick wall" digital) limiting.  (everything below 4dB remains linear.)  They also say that the converter cannot be clipped as a result.

Are functions such as these (yours & dbx's) implemented within the A/D itself by means of a digital algorithm...or pre-staged?  I remember reading somewhere (maybe Brad's forum) where you said that this can be accomplished in both the hardware & software worlds; and was wondering if; with some of the better plug-in limiters on the market...where they offer so-called "soft clipping", if that is in any way similar to yours (or anywhere near as effective)?

Thanks,

mark4man



I do not have the time to examine in detail what dBX did. Their paper is dated 1998, and mine was done in 1995.
At first glance, what they do is fundamentally different then what I do.
To quote you: "They also say that the converter cannot be clipped as a result".
I do not have any such claims. I do my process on the converted data, AFTER the conversion, thus I do not claim that the converter can not be clipped. The idea with mine is to boost the level by up to 1 bit (up to 6dB) for all signals bellow -12dBFS, but that means that the range of 0 to -12dBFS needs to be "squeezed" into 6dB range. So the signal peaks are "flatter", they not clipped, they are "gently pushed down". But if you overdrive the converter, you will clip the signal (flat top).
Such a process is a lot more difficult to accomplish then first meets the eye. It is not a simple matter to get sonically acceptable results, because unlike analog, in the digital world, the harmonics due to non linear processing do not all end up at higher and higher frequencies. In digital, there is aliasing, and the harmonics you wish to eliminate go way up there (from the ear stand point) because the ear is "nearly  logarithmic". Of course, there is no way to filter the energy that gets aliased, because they are "manufactured" by non linearity, so by the time you see them, they are already aliased (thus inseparable from the audio).

All those soft limits and saturation processing should be used with care. Some music "wants you to stay linear", other music "likes" the effect.

One factor often discussed by the EE's in the pro audio community is about keeping some margins away from full scale, because some up sampling DA's may "fill in" samples beyond full scale. Unfortunately most high quality studio "monitoring" DA's do not show what many consumers will hear. So I recently tried to "soften" the top 1.5dB on my converters. Some mastering engineers love it, but some did not (I will do it as a "special request"). The reason I throw he above comment in - the digital soft saturation can be helpful in alleviating the rather common practice of "driving beyond the rails" for the sake of "being louder". It is a compromise, and it is difficult to quantify, so I leave that decision to the ears of the mastering engineers.

Regards
Dan Lavry
http://www.lavryengineering.com
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mark4man

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Re: AD-122 "Soft Saturation" Question for Mr. Lavry
« Reply #2 on: September 27, 2006, 07:53:12 PM »

Quote:

I do my process on the converted data, AFTER the conversion, thus I do not claim that the converter can not be clipped. The idea with mine is to boost the level by up to 1 bit (up to 6dB) for all signals bellow -12dBFS, but that means that the range of 0 to -12dBFS needs to be "squeezed" into 6dB range. So the signal peaks are "flatter", they not clipped, they are "gently pushed down". But if you overdrive the converter, you will clip the signal (flat top)

Dan...

Thanks for the response...& I think I understand your process better, now.  So...if soft saturation is engaged in the mastering process (outputting a client's mix from one workstation & capturing w/ the AD-122 to the second); & I'm not slamming the A/D's input (since you say it will clip)...since the process occurs after conversion, is there some sort of make-up gain stage involved, so as to achieve a little bit of extra loudness on that side?

The reason I ask is...for the client who is satisfied w/ the sound of their mix; & only wants additional gain on their master, w/o the coloration of compression/limiting...I am told that the AD-122 is the premier tool for this job (clean extra gain w/ no loss in punch, clarity & high fr.'s.)  But they all talk as tho they are hitting the A/D fairly hard.  I'm thinking about grabbing one of these units; & as such trying to figure out how it could be used in this regard...but, could it be (based on your description) that they aren't realizing the extra gain is accomplished post conversion?

(should I just download & read the manual...is it all in there?)

Thanks again,

mark4man


Update...OK...read that section of the manual & think I have it now.  The +3dB & +6dB settings boost the overall signal by that amount in the linear range & soft limit the logorithmic range...so as to output a hotter (hotter by +3dB & +6dB respectively), yet legal, signal (0dBFS ceiling.)  Is that correct...the extra gain comes in that form?
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danlavry

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Re: AD-122 "Soft Saturation" Question for Mr. Lavry
« Reply #3 on: September 28, 2006, 04:59:50 PM »

mark4man wrote on Thu, 28 September 2006 00:53

Quote:

I do my process on the converted data, AFTER the conversion, thus I do not claim that the converter can not be clipped. The idea with mine is to boost the level by up to 1 bit (up to 6dB) for all signals bellow -12dBFS, but that means that the range of 0 to -12dBFS needs to be "squeezed" into 6dB range. So the signal peaks are "flatter", they not clipped, they are "gently pushed down". But if you overdrive the converter, you will clip the signal (flat top)

Dan...

Thanks for the response...& I think I understand your process better, now.  So...if soft saturation is engaged in the mastering process (outputting a client's mix from one workstation & capturing w/ the AD-122 to the second); & I'm not slamming the A/D's input (since you say it will clip)...since the process occurs after conversion, is there some sort of make-up gain stage involved, so as to achieve a little bit of extra loudness on that side?

The reason I ask is...for the client who is satisfied w/ the sound of their mix; & only wants additional gain on their master, w/o the coloration of compression/limiting...I am told that the AD-122 is the premier tool for this job (clean extra gain w/ no loss in punch, clarity & high fr.'s.)  But they all talk as tho they are hitting the A/D fairly hard.  I'm thinking about grabbing one of these units; & as such trying to figure out how it could be used in this regard...but, could it be (based on your description) that they aren't realizing the extra gain is accomplished post conversion?

(should I just download & read the manual...is it all in there?)

Thanks again,

mark4man


Update...OK...read that section of the manual & think I have it now.  The +3dB & +6dB settings boost the overall signal by that amount in the linear range & soft limit the logorithmic range...so as to output a hotter (hotter by +3dB & +6dB respectively), yet legal, signal (0dBFS ceiling.)  Is that correct...the extra gain comes in that form?



First. I am not exactly logarithmic, nor do I think that a log is the best way to go, there are other issues about it counts more.

Second, that "I want it louder" is not uncommon. There are a lot of folks that want to be the loudest (relative to other material) and some well known mastering guys drive converters real hard into saturation. It is a "compromise" between pure sounds vs. louder but with some distortions.

The AD122 MKii and AD122 Mkiii handle "hits" into clipping with as much grace as possible. I wish people just did not clip, so I made the digital saturation which enables louder sound but without the clipping (rounding off instead of "flat top")...

I will have to leave the decision what to do to your ears. You can be sure that clipping will measure as distortions, but as we know, the word distortions covers a wide range of "signal alterations", some are very offensive, others less offensive.
There are some very good mastering engineers that figured out that they can get a good compromise by driving into clipping. Yes it is gear dependent...

Regards
Dan Lavry
http://www,lavryengineering.com
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