Avid Pro Audio Community

Avid Pro Audio Community

How to Join & Post  •  Community Terms of Use  •  Help Us Help You

Knowledge Base Search  •  Community Search  •  Learn & Support


Avid Home Page

Go Back   Avid Pro Audio Community > Pro Tools Software > Tips & Tricks

Reply
 
Thread Tools Search this Thread Display Modes
  #21  
Old 10-13-2001, 05:37 AM
Jules Jules is offline
Member
 
Join Date: Dec 1999
Location: London, UK
Posts: 2,565
Default Re: setting record levels into ProTools with the intent of mixing in ProTools

Man! That is some hard **** to understand!
All I know is the new Sony Plug is amazing.. I am on the Dithered mixer BTW - just to be 'trendy' I geuss.

[img]images/icons/shocked.gif[/img]
__________________
Jules
London, UK
Come hang with us here!
www.gearslutz.com
Reply With Quote
  #22  
Old 10-13-2001, 09:58 AM
Park Seward's Avatar
Park Seward Park Seward is offline
Member
 
Join Date: Jul 2001
Location: Grants Pass, OR
Posts: 4,284
Default Re: setting record levels into ProTools with the intent of mixing in ProTools

From the Answerbase,

What follows was submitted to the DUC by Dave Lebolt.

From what I've been able to learn, a well-designed 24-bit fixed point digital audio system is *equal to (or better than)* a well-designed 32-bit floating point system.
This issue is difficult to educate people about, because it's a bit like trying to differentiate between Intel CISC processors (used in PCs)
and PowerPC RISC processors (used in Macs). Some people tend to look at the number "32" and say it's bigger than "24" and they're done. But it's not so simple...
32 is Better Than 24, Right?
Not really... Remember, we're not strictly talking about 32 bits representing the audio signal here
*(the bit depth or word length).* The signal recorded to disk and sent in and out of the I/Os on all of these DAW or mixing systems is still
16- or 24-bit (not 32-bit). Instead, we're talking about how the programmer works with the math results when they're performing mixing and processing operations.
What Does "Floating Point" Mean?
Floating point arithmetic allows a programmer to represent the result of complex equations so that the number of digits representing the exponent and mantissa can "float" or "move." This translates to a more flexible scheme for representing very small numeric values (values between +1,0, and -1) which are the remainders from their calculations. It does not necessarily represent greater numerical precision,
however (for example, we hold on to 48 bits of precision with our fixed point math until we truncate it on output).
Floating Point vs. Fixed with Digital Audio
In a digital audio system, most every time mixing or processing occurs the result of the calculation will be a long integer (another way to say "big number"). When working with 24-bit audio, those numbers get pretty large, because the results
of the calculations (if listed in standard base 10) would have many places after the decimal point. A properly designed audio system will try to maintain as much accuracy as possible when manipulating the bits, to avoid losing resolution.
Loss of resolution can result in poor audio quality. (Some changes would not be audible to most people, but could be audible to "golden ears" people.)
The programmer attempts to "hold onto" the remainders from these equations as accurately as possible as more and more them take place. At some point, however, they've got to do one of two things:
- Truncate or round the result (cut off the numbers that they can't "hold onto" anymore)
- Apply dither to the result and then round to the lower number of bits. Dither injects a low-level
non-correlated noise into the signal to avoid distortion artifacts caused by quantization,
by reducing those artifacts to white noise. Repeated applications of dither will raise the noise level, but proper use of dither can offer better results. This process happens in all systems, whether fixed or floating point. Remember, the programmer has to eventually round, truncate or dither the numeric precision they've been "holding on to" when they send a file to disk or out of the system. This is because the word length is fixed at 24 (or 16) bits. And, keep in mind that audio that comes in to converters on a Pro Tools system and gets
sent to disk, is sent there unaltered.
Our DSPs vs. Their DSPs
In our system, we use the 56-bit accumulator that is in the Motorola DSPs we use to store values as we do the math. This means that you can get a very high level of precision. The "24-bit Optimized" mixer that we have shipped since Pro Tools|24 was released stores 48-bits of precision in our mixing operations. This allows for high headroom (close to 28 dB). At the point when the data is placed on a physical output or into a submixed Aux input or send, the output is truncated to 24 bits of precision. This new mixer that we're giving out for "golden ears" evaluation *dithers*
the output streams instead.

From: http://answerbase.digidesign.com/ABa...WEB&-response= ABdisplay.lasso&-logicalOp=or&-recordID=43805&-token.myToken=noise&-search
__________________
Park
The Transfer Lab at Video Park
Analog tape to Pro Tools transfers, 1/4"-2"
http://www.videopark.com
MacPro 6 core 3.33 GHz, OS 10.12.1, 8 GB RAM, PT12.6.1, Focusrite Saffire Pro 40, PreSonus DigiMax, MC Control V3.5, dual displays,
Neumann U-47, Tab V76 mic pre, RCA 44BX and 77DX, MacBook Pro 9,1, 2.3 Mhz, i7, CBS Labs Audimax and Volumax.
Ampex 440B half-track and four-track, 351 tube full-track mono, MM-1100 16-track.
Reply With Quote
  #23  
Old 10-13-2001, 10:34 AM
Park Seward's Avatar
Park Seward Park Seward is offline
Member
 
Join Date: Jul 2001
Location: Grants Pass, OR
Posts: 4,284
Default Re: setting record levels into ProTools with the intent of mixing in ProTools

I'd like to present a different view.

The S/N ratio of 16 bits is 98 db and (I think) 24 bits is 148 db.

Distortion in the digital realm is bad. Nasty sounds.

If you attempt to record at the very highest level, you run the risk of adding that nasty digital distortion created by very fast, high amplitude peaks that your meters are too slow to show you. This practice of recording close to zero may be responsible for the harshness some complain about in digital recordings. What we may actually be hearing is distortions caused by hot level recordings.

If the signal-to-noise ratio is 148 db, are we really concerned with an extra 10-20 db of noise? There is no microphone/mic pre chain that can come close to that spec. Thermal noise itself is much higher than -148db.

You could reduce your gain by 10 db and never hear the additional noise. A 138 db ratio is still the difference between the quietest whisper and a jet plane taking off.

That extra 10 db of headroom may reduce distortions of fast transients and may improve the overall quality of your recordings.

So a -18 db operating level that is used in professional videotape recordings may be a good choice.

Also, find the "sweet spot" of your system. It is not usually "all the way up".

I started in analog recording and the noise floor was a major concern at -50 to -70 db, so I may have a different perception of noise than someone who started in digital. I would take a little noise over digital distortion, for example.

Just another view.
__________________
Park
The Transfer Lab at Video Park
Analog tape to Pro Tools transfers, 1/4"-2"
http://www.videopark.com
MacPro 6 core 3.33 GHz, OS 10.12.1, 8 GB RAM, PT12.6.1, Focusrite Saffire Pro 40, PreSonus DigiMax, MC Control V3.5, dual displays,
Neumann U-47, Tab V76 mic pre, RCA 44BX and 77DX, MacBook Pro 9,1, 2.3 Mhz, i7, CBS Labs Audimax and Volumax.
Ampex 440B half-track and four-track, 351 tube full-track mono, MM-1100 16-track.
Reply With Quote
  #24  
Old 10-13-2001, 11:24 AM
sdevino sdevino is offline
Member
 
Join Date: May 2001
Location: Derry, NH USA
Posts: 410
Default Re: setting record levels into ProTools with the intent of mixing in ProTools

Tracking at 0dBFS is a REALY BAD idea as was mentioned in the previous post.

24 bits = 144 dB of dynamic range.
The thermal noise on the input to an Apogee or PT A/D limits the dynamic range to about 110dB (I am being nice). That means that the last 34dB of dynamic range you got from the 24 bit converters is below the noise floor.

If you track at -18dbFS you still get 18 dB of head room for fast transients and impulses (like high hats) and an average 92 dB signal to noise which is still much quieter than analog tape.

Try tracking at -18 dBFS and watch how much better your mixes sound.
Tracking as close to 0 dBFS creates all kinds of digital clipping noise which sounds like s%^t.

Steve
__________________
Steve Devino
Granite Rocks Live
Authorized Metric Halo Dealer
1-603-867-6843
Reply With Quote
  #25  
Old 10-13-2001, 03:36 PM
Mike Tholen Mike Tholen is offline
Member
 
Join Date: Dec 2000
Location: Chicago
Posts: 329
Default Re: setting record levels into ProTools with the intent of mixing in ProTools

why doesn't everyone get it?
Observe 0dBVU. [img]images/icons/wink.gif[/img]

I've been round and round with this "issue" for a while now.
I use VU meters to check the output of my pres, then when optimun operating levels ensues I then take that signal and input it into PT.
I do not adjust the level any higher after that to achive a hotter signal as my VU shows that my signal is at 0dBVU which is -18dBFS. simple. [img]images/icons/shocked.gif[/img]
Reply With Quote
  #26  
Old 10-13-2001, 08:38 PM
Park Seward's Avatar
Park Seward Park Seward is offline
Member
 
Join Date: Jul 2001
Location: Grants Pass, OR
Posts: 4,284
Default Re: setting record levels into ProTools with the intent of mixing in ProTools

Thanks Mike and Steve. You are exactly right.

Seems the newbies hear that "louder is better" and try to get just below "0".

I agree with you both.
__________________
Park
The Transfer Lab at Video Park
Analog tape to Pro Tools transfers, 1/4"-2"
http://www.videopark.com
MacPro 6 core 3.33 GHz, OS 10.12.1, 8 GB RAM, PT12.6.1, Focusrite Saffire Pro 40, PreSonus DigiMax, MC Control V3.5, dual displays,
Neumann U-47, Tab V76 mic pre, RCA 44BX and 77DX, MacBook Pro 9,1, 2.3 Mhz, i7, CBS Labs Audimax and Volumax.
Ampex 440B half-track and four-track, 351 tube full-track mono, MM-1100 16-track.
Reply With Quote
  #27  
Old 10-13-2001, 09:07 PM
Felix Felix is offline
Member
 
Join Date: Dec 1999
Location: Portland, Oregon
Posts: 1,012
Default Re: setting record levels into ProTools with the intent of mixing in ProTools

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:<HR>Originally posted by Park Seward:
Thanks Mike and Steve. You are exactly right.

Seems the newbies hear that "louder is better" and try to get just below "0".

I agree with you both.
<HR></BLOCKQUOTE>

well, it seems that there's more to it than what any 'newbies' hear and think.
why does Digidesign, in the ProTools manual, instruct its' users to record as close to 0 dbFS as possible?
Reply With Quote
  #28  
Old 10-13-2001, 10:59 PM
Park Seward's Avatar
Park Seward Park Seward is offline
Member
 
Join Date: Jul 2001
Location: Grants Pass, OR
Posts: 4,284
Default Re: setting record levels into ProTools with the intent of mixing in ProTools

Please find the page where the manual says to "record as close to 0 dbFS as possible". I couldn't find it. I did find:

Set Input Levels High But Don’t Clip
When you feed a signal into any audio recording
system, including Pro Tools, you need to adjust
the input level to optimize the dynamic
range. Adjust the input signal to register as high
as possible on your input meter without triggering
the clipping indicator. If the input level is
too low, you will not take full advantage of the
dynamic range of your Pro Tools system. If the
input level is too high, however, it will be
clipped."

Sounds like they are recommending to not clip the signal. So did I when I said to lower the level so you don't clip levels you can't see on the meters. And I would re-write that paragraph to have different advice for 24 bits vs. 16 bits.

Send me that page number please.
__________________
Park
The Transfer Lab at Video Park
Analog tape to Pro Tools transfers, 1/4"-2"
http://www.videopark.com
MacPro 6 core 3.33 GHz, OS 10.12.1, 8 GB RAM, PT12.6.1, Focusrite Saffire Pro 40, PreSonus DigiMax, MC Control V3.5, dual displays,
Neumann U-47, Tab V76 mic pre, RCA 44BX and 77DX, MacBook Pro 9,1, 2.3 Mhz, i7, CBS Labs Audimax and Volumax.
Ampex 440B half-track and four-track, 351 tube full-track mono, MM-1100 16-track.
Reply With Quote
  #29  
Old 10-13-2001, 11:52 PM
Corey Shay Corey Shay is offline
Member
 
Join Date: Dec 1999
Location: Orlando, FL, USA
Posts: 755
Default Re: setting record levels into ProTools with the intent of mixing in ProTools

Well, gee, I dunno that looks pretty clear cut to me. I would think that to "record as close to 0 dBfs as possible" implies the (without actually clipping) common sense. "Adjust the input signal to register as high as possible on your input meter without triggering the clipping indicator" seems to be one in the same. After all, "as high as possible" in any digital system = 0 dB fullscale. And the clip light in PT seems to trigger somewhere in between -0.1 dB and 0 dB. Close enough. I think you found the page right there. What page number is that anyway?
Reply With Quote
  #30  
Old 10-14-2001, 08:50 AM
snoopy snoopy is offline
Member
 
Join Date: Jul 1999
Location: Hollywood CA
Posts: 744
Default Re: setting record levels into ProTools with the intent of mixing in ProTools

SO what is bing mplied is that PT will record signals that go above 0 dbfs(thus clipping) but the clipping light will not go off? Is it me or does it seem odd that the computer wouldn't know that it is going over 0?

I don't doubt that many people have better results recording at lower levels, but I can honestly say I get great results recording at high levels. I don't slam anything, but I make sure the peaks are pretty darn close to 0dbfs. I guess it's simply the classic case in audio of what works for one person doesn't for another, and vice versa. I keep my 888's at -14 instead of -18 so I don't have to push the outputs of the outboard gear as much to get closer to 0dbfs. I suppose if you were set to -18 and tried to always reach 0dbfs you probably would get sound degredation from the outboard gear. I'm no techie so I can't contest any of the technical data, but I am happy with my results. I have clients that have J9k rooms themselves but prefer the PT mixes I get at my studio so they will come to me. This is of course a subjective scenario, but it makes me feel better about my methods.
__________________
Colin Miller
Teaboy Audio Recall Sheets
http://teaboyaudio.com
Reply With Quote
Reply

Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump

Similar Threads
Thread Thread Starter Forum Replies Last Post
Need Help Setting up My Firestudio to Record in ProTools gonzokarate Getting Started 2 11-08-2013 03:19 AM
Need some help setting up ProTools to record with Eleven Rack thrashmetl Eleven Rack 19 08-11-2013 11:11 AM
Setting Record Levels GTBannah 003, Mbox 2, Digi 002, original Mbox, Digi 001 (Win) 2 01-29-2007 11:37 AM
Record enabled tracks, setting levels LSW 003, Mbox 2, Digi 002, original Mbox, Digi 001 (Win) 3 11-23-2006 08:05 PM
Setting fader levels for maximum mixing headroom Siberian 003, Mbox 2, Digi 002, original Mbox, Digi 001 (Win) 5 10-07-2003 05:43 AM


All times are GMT -7. The time now is 03:31 AM.


Powered by: vBulletin, Copyright ©2000 - 2008, Jelsoft Enterprises Limited. Forum Hosted By: URLJet.com