Need advice on Mastered CD level

Discussion in 'Mastering' started by neomystic, Feb 14, 2005.

  1. neomystic

    neomystic Guest


    I have a CD I am in the process of re-releasing. It was mastered by Future Disk Systems back in 1993. I only have the DAT copy that I received from the mastering house.
    To make a new CD master, I hooked up my DAT machine to Protools and copied the DAT tracks each into a PT session using 0 db settings on faders. This resulted in dual mono files being created. I then bounced to interleaved stereo. I did not use a master track in PT.
    When the bounce completed I loaded the tunes into roxio jam. That's when I noticed the levels turning on the red clip leds on each loud passage. I also loaded the same material into bias peak express and got the same result.
    The two mono tracks in PT never hit the red but if I create a master fader it will light the red.
    I did a check to see how much too high the level was. In jam and in peak I only have to decrease the level .1 db to avoid the clipping lights. Howevert, in PT with the master fader it rquired about 3 db antinuation.
    I can't really hear any clipping in spite of the clip lights.

    My questions are these:

    Should I correct the levels or not?
    Should I use Jam to lower the level .1 db?
    Why the effect that I saw in PT with master fader vs no master fader?

    PS. I loaded a ZZ Top greates hits CD to see how it looked. One song was exactly like what I see on my CD but the others were quite a bit lower in level.

    Any insite from an experience pro would be most helpful and appreciated. Two mp3 tracks from the cd that were made from the same PT files can be heard at the link below

  2. Michael Fossenkemper

    Michael Fossenkemper Distinguished past mastering moderator Well-Known Member

    Different meters will light up at different levels. If you load in digital at zero, then it's the same level. You can also import dual mono into jam, you don't have to bounce again. You can lower the output if you want, but it's not necessary. But if you do lower the level, you'll have to dither it. In 93', they were probably clipping to get the level. Plant it's going to care. I'd just leave it.
  3. neomystic

    neomystic Guest


    Thanks for the help. I didn't realized I could import the dual mono into jam. That could of saved me some time. I think I'll take your advise and leave it alone. Back to my tracking and mixing.......

  4. blueinkpen

    blueinkpen Guest

    I'm not familiar with ProTools but if you panned one track hard left and the other hard right, it may be increasing the level in the channel to compensate for the lower level in the other (I know Vegas does this). In Vegas, you can change how the pan control pans; not sure about PT.

    The reason it only took .1 db atenuation in jam is because the audio was already clipped when you bounced down to stereo so once you brought it down just a hair, it didn't detect it anymore.

    But like the last poster said, the best would be to import dual mono instead. That way, neither channel should have any gain (as panning does) at all.

  5. Reggie

    Reggie Well-Known Member

    Yeah, I forgot to look last night, but Cubase has some kind of setting that has to do with how it treats stereo information or something. Mine defaults to -3db, but maybe PT doesn't have this default. I think it has to do with a left channel peaking at 0 plus a right channel peaking at 0 equals a sum of +3db. So that is why it does the compensation. But I may be way off here; just going on memory and assumption.
    If it sounds really bad when you put it on CD (and you will know if it is clipping more than it should), then I would do the adjustment.
  6. neomystic

    neomystic Guest


    You hit the nail on the head. As soon as i read the word "pan" in your post i new what was wrong. In the PT session the dual mono audio tracks were each panned to the center. They should have been hard left and right. The fact that i needed to antenuate the master fader 3 db should have been my clue because the two signals were summing on the stereo bus. I gues i got confussed by the .1 db antenuation needed in jam and didn't take the clipping into consideration. Thanks for thinking this through for me.

    I did the dual mono import in jam and got a good result and no clip lights even though the level goes up to within tenths of a db of the red line. This is more as I would expect.
    Now i have to go back and look at the mp3 files i made using this process 5 years ago. (yikes)

    It's so easy to screw up in this world.

    thanks again
  7. mixandmaster

    mixandmaster Active Member

    If you would have created a stereo audio track in ProTools, it would have automatically panned them. I never thought of them being in mono or I would have suggested that in the first place. Sorry, but a GREAT catch by Reggie.
  8. Nika

    Nika Guest

    Something to keep in mind is how close you want to be to clipping anyway. I would advise reading the paper about digital distortion here:

    MKH 800's

    It is a short read and may help you out.

  9. Ammitsboel

    Ammitsboel Member

    Nika, the issue of adjusting a fader in a DAW has far more quality consequence than the fact of being very close or less than close to clipping IMO.
  10. Nika

    Nika Guest

    Unless the software is severely broken I can't see why this would be the case. What would simply multiplying all data by a fixed coefficient and then dithering off the bottom bits due to the sound - unless the dither was poorly applied?

  11. Michael Fossenkemper

    Michael Fossenkemper Distinguished past mastering moderator Well-Known Member

    Added noise??? that's one reason. It also depends on how much it's clipped. But as he's pointed out, it's fine so why F*ck with it. The more variables, the more potential problems. there are very few engines that don't degrade the audio somehow.
  12. Nika

    Nika Guest

    Now wait a second. You drop the signal by, say, 2dB when it's 24 bit data, necessitating dithering it back to 24 bits after the calculation, which adds noise at a level of -141dB FS. Then you dither it to 16 bit and you complain about the noise added at -141dB FS? At what level do you have to monitor to hear noise at -141dB FS?

    Something about this claim seems very specious.

  13. Michael Fossenkemper

    Michael Fossenkemper Distinguished past mastering moderator Well-Known Member

    It's a 16 bit file, it's coming from DAT.
  14. Nika

    Nika Guest

    And we're editing as 16 bits? Why in the world? We should first importing it into a 24 bit session at minimum. Then we wouldn't have the noise problems you're indicating.

  15. Ammitsboel

    Ammitsboel Member

    I know you can't see it.
    I also know why you say as you do.
    I'm just saying that I've never heard a fader in a DAW that didn't degrade the sound in some maner.

    This is bread and butter for a ME so you should know about this.

    Also, asking a novice to level adjust material that he already has got mastered is simply the wrong thing to do. He will be degrading the sound quality for absolutely no reason.

    Best Regards
  16. Michael Fossenkemper

    Michael Fossenkemper Distinguished past mastering moderator Well-Known Member

    Especially if he liked what he got and didn't want to change it.
  17. Michael Fossenkemper

    Michael Fossenkemper Distinguished past mastering moderator Well-Known Member

    Whether or not it's a 24 bit session or a 16 bit session. Dither for a 16 bit file sits at the bottom of the 16 bit file. That you can hear. If it's noise shaped, then you'll hear the effects of that too.
  18. Nika

    Nika Guest

    This sounds like mythology to me. Can you take a 24 bit signal, drop it by 3dB. Raise it by 3dB and hear a difference? Can you see the difference on a null test? How does the difference manifest itself. I'd like to see this on a fixed point system such as Protools TDM.

    What is bread and butter is that many people say this. What is not bread and butter is that it happens.

    Agreed there.

  19. Nika

    Nika Guest

    Dither for the 16 bit file sits at -96dB FS or so. When I open it into a 24 bit session I now have dither at -96dB FS or so but I also added noise at the -144dB FS level. The overall gain to the noise is +.03dB, from around -96dB FS to around -95.97dB FS.

    As for "hearing the effects if it's noise shaped," what do you mean by that? Since gain change is a linear process how will that manifest itself in an audible way?

  20. Michael Fossenkemper

    Michael Fossenkemper Distinguished past mastering moderator Well-Known Member

    If you use a radical noise shaped dither like UV22 or Pow-r #3 or whatever, you can hear it excentuate certain upper freqs. If you have an arsenal of different dithers, pop them in and out and listen to what it does to the audio. It's not as linear as you may think.

    As for noise added, depends on the dither and at what freq's. It's also random and not static.

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