DeeringAmps


Well Ben here is your "Smoking Gun"
pg 15 post #430
Q "So, to clarify, there is no difference, audio quality wise, between hitting your input converters soft or hard, e.g. with maximum peaks at -18dbfs and no gain change at the channel head, compared to -1dbfs with a 17db level cut at the channel head?
The reason I ask is that I think I've heard someone say that hitting you AD converter hard can degrade the audio quality a little bit."
A) "That depends entirely on the ADC design, quality and performance - and indeed whether it deliberately distorts to avoid clipping :-(.
Whilst it is true that hitting the ADC hard will increase signal to noise ratio, there's also the risk that it may produce more harmonic distortion - or even overloads sawing off your peaks (or other stuff which is more complex)."
I admit defeat! Ben will NOT want to hear the rest of the answer, but others might...
"If you can't test accurately what your ADC actually does (very difficult) then my advice is to aim for -6dB peak values out of your converter as a reasonable safety compromise (only losing 6dB SNR) - and then lose perhaps another 6dB at the head of your DAW channels - giving you total headroom of around 12dB for your mix and processes."

What was it Danny said in the other thread about "peak" values on his tracks?

But again, I admit DEFEAT...

T

It wasn't about winning mate, it was about answers and Danny and I both were of the same mind -6db peak is a good place to be although I am not adverse to peaks as high as -3db because I'm a raceing car driver and I like to skirt the edges a bit plus even if you do clip as long as it's just a click I know a trick or two to disguise it.
 
Ok so we get this straight, this had nothing to do with right or wrong, I had made some claims and I was told to shut up and go away and poop, so I decided to put up.
 
I was shot down again but it would seem even though the myth was debunkend, there is some truth as well, The Amazing World of Digital.
 
What has come of this is we have an optimum operating level for our digital recording and mediums.
 
We have an idea that we should think of our DAW's as analouge mixing desks and not be afraid to use the trim, this is something that I wanted to put out there as well, not understanding this concept of gain structure, even now in the audio courses I did and when I posted on another forum the idea of using trim, the answer was Huh and this was by the supposed "pros"
 
So I hope you all understood this was nothing to do with right or wrong but an exercise in working together to find some answers and we found answers, I know I am a bull in a china shop but we need bulls and we need pussy cats, if the world was only populated with bulls well you know how that would end and sometimes pussycats turn out to be tigers.
 
Neb

weather you guys are trying to revial the truth or find the ever so elusive invediable,this thread is really good and educating,thanks for the read guys.

seriously,

very intersting stuff.

Ben in case you don't get onto that article here is the jist of it in point form.

*     As I said there were not a lot of 24 bit interfaces around at the time of Stav's approach to recording higher for 16 bit. They are all 24 bit now, hence the reason we can use 24 bit so easily.

*     There is analog electronics even inside your A to D converters right before the converter part and the noise floor of those stages will be worse than the 24 bit digital noise floor.

*     Not all the bits of a 24 bit system are used. In the article it states more like 21 bits out of the 24 are being used.

*     Something that is not considered is that every time you add a track to a multitrack session the digital noise floor is in fact rising slightly. For one  or two tracks it is not a biggie but when you get into 32 tracks for example in 16 bit mode the noise floor comes up.

With 4 db of headroom 32 channels will create a noise floor of around -64 dB. (it gets 6 db worse as you double the tracks so for a 64 track mix the digital noise floor is -58dB) Good news is in 24 bit mode a 32 channel mix is creating a total digital noise floor of way down at -112 dB! MUCH better than in 16 bit mode. Where 24 bit excels is when you have large numbers of tracks.

*     Final conclusion is recording down at -20 dB rms is perfectly fine and very good. There is no improvement in sound quality or nothing to be gained sound wise by recording hotter.

The whole concept of thinking like the old analog days is simply right and excellent! Just create your rms levels down at K-20 for example and treat the whole digital system like an analog system. Hence the reason why the K system approach works so well. You still need some sort of VU meter to show you 0dB VU when you are down at -20 dB FS. Peak meters are also important for transient signals but VU's are required if you in fact want to operate a digital system in an analog way.  (that is what SSL tell us too with the AWS948)

Jeff Evans


*     Something that is not considered is that every time you add a track to a multitrack session the digital noise floor is in fact rising slightly. For one  or two tracks it is not a biggie but when you get into 32 tracks for example in 16 bit mode the noise floor comes up.

With 4 db of headroom 32 channels will create a noise floor of around -64 dB. (it gets 6 db worse as you double the tracks so for a 64 track mix the digital noise floor is -58dB) Good news is in 24 bit mode a 32 channel mix is creating a total digital noise floor of way down at -112 dB! MUCH better than in 16 bit mode. Where 24 bit excels is when you have large numbers of tracks.

 

This part sounds highly questionable (and that's being generous).

Jeff and Drew wanting to have the last word are muddying the water, what has come of this is two or three importent things:

1) Digital mediums and recording devices do have an optimum operating level, in this case both danny, myself and this paul frindle agree -6db, although I have said the odd peak of -3db is alright.  And I mean odd!!

2) The mixer in your DAW's should be treated like an analouge mixer, USE THE TRIM, it is your friend, here is a diagram of how much 32 tracks of summed audio creates http://www.prosoundweb.com/article/setting_sound_system_and_mixing_console_gain_staging/av/P3/ what this means is even before you start mixing and if you have all faders at unity you are already 15db over 0dbfs, so if you are going to mix 32 tracks turn the main buss trim down so you have headroom.  Because we all know digital has no headroom so, you have to create it.

3) Even though it still seems to be a point of conjecture, somewhere in the digital signal processing chain, harmonic distortion happens, so if this is the case listen for it when setting levels as it goes into the DAW.

As for the other stuff, it's all well and good but even I am struggling with it, I think the three above points are the most importent ideas that we have gained out of this disscusion.

And as I have pointed out before, it took them over 29 years to figure analouge out.

From the moment Bing and Les Paul, using stolen German technology figured out mulit track tape recordings and did the first home recordings in 1946, to the epitomy of multi-track tape recording or to put it plainly when tape could go no further.  Which in my opinion is Bohemian Rhapsody, this is 1975.

Funnily enough the first digital recorder appeared on the market in 1977, If I remember correctly, so 35 years to get to the point where we are now, hmm funny about the similar timeframe.

The problem with digital is the goal posts keep moving, from the 13 bit digital recorder of 1977, to 16 bit in the mid-80's finally the not so 24 bit of now.

But we now I believe have three constants that we can say yes to, and reiterate, that digital has an optimum operating level, that digital mixing should be treated the same as analouge mixing and that somwhere in our little boxes somewhere in the signal chain, some form of harmonic distortion is happening and if it's pleasent aim for it.

Neb 

BenMMusTech


Jeff and Drew wanting to have the last word are muddying the water, what has come of this is two or three importent things:

1) Digital mediums and recording devices do have an optimum operating level, in this case both danny, myself and this paul frindle agree -6db, although I have said the odd peak of -3db is alright.  And I mean odd!!

As I said before (repeatedly), anywhere the quantization level is reasonably far below the noise floor and you aren't clipping is "optimal".

We can go through it all again if you'd like.

One-man wolf pack 

drewfx1

BenMMusTech


Jeff and Drew wanting to have the last word are muddying the water, what has come of this is two or three importent things:

1) Digital mediums and recording devices do have an optimum operating level, in this case both danny, myself and this paul frindle agree -6db, although I have said the odd peak of -3db is alright.  And I mean odd!!

As I said before (repeatedly), anywhere the quantization level is reasonably far below the noise floor and you aren't clipping is "optimal".

We can go through it all again if you'd like.

Then why this:
 
"If you can't test accurately what your ADC actually does (very difficult) then my advice is to aim for -6dB peak values out of your converter as a reasonable safety compromise (only losing 6dB SNR) - and then lose perhaps another 6dB at the head of your DAW channels - giving you total headroom of around 12dB for your mix and processes."
 
And what about the prospect of the mere posibility of harmonic distrotion in you black box!!! 
 
I think you might have the science correct but I think the science is still pissing in the wind, 29 years to figure out tape and after 35 years we are still trying to figure out digital and the possibility's.
 
The three points I have made have nothing to do with the maths, screw the maths, it has to do with three people's opinion that there is an optimum operating level for digtal and this may tie in with this idea of harmonic distortion.
 
So even if the harmonic distortion is before the converter, at -6db we are going to hopefully pick some of that extra harmonic distortion up.
 
Sorry drew I am going with my ears and heart on this one, you may get the maths but something else is going on.  That ramdom factor that even maths most of the time can't explain.
 
Neb 

drewfx1 I am only quoting the article in question and why would 32 tracks not add some noise like they used to in the analog days with each one contributing some level of hiss. Except in the digital world the noise or quantisation error noise is much lower but why would it not add up. In 16 bit mode 64 tracks could be considered noisy. (assuming they are all up around unity and in the mix)

Analog does tend to have optimum levels so we need to be aware of them and set our levels there. Ben  is wrong however stating that digital has an optimum level, it does not.  As long as you are not down at some very low level eg -60 dB or so what I have said is simply this, you can record at quite a wide range of levels digitally and there will no change to the sound quality. My ears and my heart are telling me this too! (there will be variances in rms levels hence some tracks will sound louder than others though so it might be wise to concentrate on consistent rms instead of peak levels)

And when any of you say record up to -6db, record what at -6db! Are you referring to a peak. Because you certainly could not track at -6dB rms could you. So if a transient makes it all the way up to -6 db then the rms part of that signal could easily be down at -14 dB or even -20 dB rms.

As I have said before forget peaks and keep track of rms levels all the way through a production and keep them at a similar level. (in my case it is K -14 dB only because my Yamaha digital mixer is calibrated there) Worry about the rms levels and the peaks will all vary above any rms level and they tend to take care of themselves.

As long as you are a nice level eg -20 dB rms then you never really have to worry about peaks because rarely will a track have a peak that is greater than 20 dB above its rms level.

That is one of the problems of digital compared to analog. Analog does have optimum levels and reference levels and we have all worked with them but digital does not and it is all over the place level wise so we are trying to give them some sort of consistecy. K system does this well. Sound quality wise I say it again there is no real optimum level for digital, other than being so low we are down in the digital noise or so high we are smashing into 0dB FS. If you keep away from those extremes you will be fine.

Jeff Evans


drewfx1 I am only quoting the article in question and why would 32 tracks not add some noise like they used to in the analog days with each one contributing some level of hiss. Except in the digital world the noise or quantisation error noise is much lower but why would it not add up. In 16 bit mode 64 tracks could be considered noisy. (assuming they are all up aound unity and in the mix)

Analog does tend to have optimum levels so we need to be aware of them and set our levels there. Ben  is wrong however stating that digital has an optimum level, it does not.  As long as you are not down at some very low level eg -60 dB or so what I have said is simply this, you can record at quite a wide range of levels digitally and there will no change to the sound quality. (there will be variances in rms levels hence some tracks will sound louder than others though so it might be wise to concentrate on consistent rms instead of peak levels)

And when any of you say record up to -6db, record what at -6db! Are you referring to a peak. Because you certainly could not track at -6dB rms could you. So if a transient makes it all the way up to -6 db then the rms part of that signal could easily be down at -14 dB or even -20 dB rms.

As I have said before forget peaks and keep track of rms levels all the way through a production and keep them at a similar level. (in my case it is K -14 dB only because my Yamaha digital mixer is calibrated there) Worry about the rms levels and the peaks will all vary above any rms level and they tend to take care of themselves.

As long as you are a nice level eg -20 dB rms then you never really have to worry about peaks because rarely will a track have a peak that is greater than 20 dB above its rms level.

That is one of the problems of digital compared to analog. Analog does have optimum levels and reference levels and we have all worked with them but digital does not and it is all over the place level wise so we are trying to give them some sort of consistecy. K system does this well. Sound quality wise I say it again there is no real optimum level for digital, other than being so low we are down in the digital noise or so high we are smashing into 0dB FS. If you keep away from those extremes you will be fine.

Jeff of course we are talking about -6db peak not RMS do you think that I am that unskilled and mad!!!
 
-6db peak in Sonar equates to -20 to -16RMS, And how can you go against the tide of opinion, including Danny and Paul Frindle -6db peak seems to be the optimum operating level of digital, I of course push it a little harder, sometimes, also I use outboard gear and MOTU has compression and EQ built into every channel I use these devices to hit the optimum operating level.
 
Man stop muddying the water, Drew and Jeff, I think we have found three points, those of us who are less experienced can use.
 
Lets leave it at that!!
 
Neb