A question about distorted software

Discussion in 'Archived Threads 2001-2004' started by Cagri, Mar 19, 2003.

  1. Cagri

    Cagri Second Unit

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    I am pretty sure that the answer to my question is "no", but I wanted to be sure. If the audio on a disc is recorded with distortion from the source, does it make the same effect with distortion caused by clipping?
     
  2. Jack Briggs

    Jack Briggs Executive Producer

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    Not sure what you're asking. When an amplifier is being overdriven to the point of clipping, it distorts (and sometimes it's not an unpleasant distortion, as when tube amps clip). But there are many different kinds of audio distortion. For a recording that was "distorted at the source" it must be a different kind of distortion.
     
  3. Cagri

    Cagri Second Unit

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    Jack, what I mean is, on some DVD s or CDs there are parts where the sound is heard as if it is distorted. Especially old CDs. Or in some DVDs the sound coming from the center is cracking in low levels, I know it isn't my receiver that clips, but the recording on the DVD is not perfect and the sound is not as good. Maybe the gear which they produce these discs cause the recording to be so, is it possible? Not every CD or DVD is produced with the same standard I guess, and if the sound recorded is somehow not "clean", if that is a possibility, does it make the same affect with clipping?
     
  4. Ted Lee

    Ted Lee Lead Actor

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    hmm...interesting question.

    i would think that, regardless of the quality of the source material, the amp would only clip once it was driven too hard.

    it wouldn't matter of you're playing a well recorded song, or a poorly recorded song. sound is sound as far as an amp goes?

    but, i'm not sure here...just guessing.
     
  5. Cagri

    Cagri Second Unit

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  6. Cees Alons

    Cees Alons Moderator
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    It's possible to make sure (well, at least 99%) that it's the CD and not your amp: turn the volume down to a very low level. Listen with your ears close to the speaker (if necessary). If it's still there, it's not the amp clipping.

    BTW, the reason I said "99%" and not "100" lies in the fact that it's theoretically possible that the signal level on the CD is just very loud but not distorted, and that you input stage (pre-amp or receiver) cannot handle it. You may safely assume that this chance is indeed very small, unless you have a very rare and deviating receiver (or use the wrong input, like a mic-connection for the CD player)

    Cees
     
  7. Cagri

    Cagri Second Unit

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    If it is the CD or the DVD, it will not be the same thing compared to clipping, rite? You will hear the distortion, but the signal going to the speakers will still be proper and clean?
     
  8. Cees Alons

    Cees Alons Moderator
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    There are many forms of distortion. One of them is clipping. This may also occur at the recording stage, so it may sound alike. But this is not very common. If it sounds like clipping it could be any stage of the amplification line. But the end-stage (power stage) is the mnost common one.

    Cees
     
  9. Cagri

    Cagri Second Unit

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    Cees, the answer I am after is probably so simple that you are assuming I already know it [​IMG]

    If it has occured during the recording stage, would it cause the same affect with the common clipping? Or is it safe, just an audio recording?

    In other words, say you are sitting in front of a speaker and recording the heavily distorted sound produced by it, with hi-end gear. This recording, when you listen to it on your system, is no different from your favourite CD, in regard to the quality of the signal wave and will do no damage, right? But if you used some gear which caused the distortion, rather than the sound itself from the speaker being distorted, if I may borrow from you, you cause distortion during the recording stage, how different is this than the previous?

    Thank you.
     
  10. Cees Alons

    Cees Alons Moderator
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    Cagri,

    You may assume that it's safe to play a CD if it's not you who cranks up the volume knob way to much.

    But here's the difficult theoretical part of the answer. IF someone would record a heavily distorted and clipped signal (and again: you may assume that they don't do that), theoretically such a signal JUST COULD damage your speaker the same way a distorted (clipped) signal from your amp could. However, it would have to be a very malign signal indeed and you probably couldn't even listen to it in your room for very long.

    So, in all "normal" cases, the answer is: playing a CD on a reasonable level (a level where no other CDs cause any problem with your gear) will NOT harm your speaker or amp, even if the sound was a bit distorted at the recording phase.

    I'm afraid the answer is not a clear Yes or No, but I hope this is what you wanted to know. [​IMG]

    Cees
     
  11. Vince Maskeeper

    Vince Maskeeper Producer

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    Cagri,

    It's the same thing either way- lthough the power at which you're driving the signal makes a difference. A distortion, clipping at any stage, is exceeding the headroom of the device and creating a squaring of the wave (cutting off the top and bottom). Even if you later reduce the level, the wave was not properly captured- and it is "squared" forever.

    Speakers cannot produce these waves properly. A bit of distorted dialog in a mix with music and other clean effects- probably won't do any serious damage to speakers-- certainly not like running a completely square signal at full gain, like you get when overdriving an amp-- but it is still the same "thing" in theory- both are waves which have been butchered and thus cannot be reproduced properly.

    -vince
     
  12. Cagri

    Cagri Second Unit

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    Sorry to keep this up this long, but I am a bit confused now. Vince, are you saying that if a distorted signal is recorded on a disc, it will stay as it is recorded, i.e. the wave is cut, and it will be sending clipped signals to the speakers forever? Because during the process of recording it hasn't been recorded as a proper signal, it will stay so on the disc, do I get it correct?

    Does this mean if you play back a CD which has distorted audio in it as in the example I have quoted in my previous post, it is the same thing as over driving your amp and cause clipping?
     
  13. Vince Maskeeper

    Vince Maskeeper Producer

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    Well, you keep saying "same thing"- and so I assume you're driving at the idea of damage. In terms of damage potential- it's not the "same thing". In terms of the basic theory as to why it happens, it is the same thing.

    Once a signal is distorted, it is distorted. Whether this happens because the mic overloaded, the mic preamp overloaded, it was overload in transfer, it was overloaded in mixing, it was overloaded to the mag, it was overloaded in DVD mastering, it was overloaded in D/A conversion in you receiver, it was overloaded from preamp to amp: it's all the same thing in terms of what happens to the signal in question.

    Now, if you have a piece of dialog that is clipped, and it is mixed in with 3 dozen other waveforms (Music, SFX, blah, blah, blah)- it is still distorted, but not the entire signal the speaker is reproducing. There are complete waves involved- but the artifact of a squared wave is still a small part of the signal.

    This is a very minor thing when compared to clipping an amp- where the ENTIRE WAVE FORM is lopped off. In addition- a small crackle in dialog is being driven with very minimal energy- where clipping an amp sends a 100% squared signal at full force.

    So again-- this question depends on what you mean by "the same". It is the same concept, why they are distorted-- but two very different degrees of % of distorted signal and force behind them.

    -Vince
     
  14. Vince Maskeeper

    Vince Maskeeper Producer

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    As a side note, I'd be interested to see one of those "shootout" type explorations of distortions on DVD tracks- because it seems so common I can't believe so many dialog tracks are created with such poor care.

    I've always been of the impression that this edginess happens in the encoding or decoding stage. Maybe some folks can post some of the worst cases they've seen on DVD- and I could do some research.

    I watched O Brother Where Art Thou last night and came across several rough passages...

    -Vince
     
  15. Cagri

    Cagri Second Unit

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    Vince,
    What I mean by "same thing" is; during the process of recording, because of one or several of the reasons you have mentioned in your post if the signal is cut at the top and bottom, that signal will be a clipped signal and it will be recorded on the disc, let's say, as a clipped one.
    When you play that disc on your player,would the signal going to the speaker be a "cut" one because it was cut during the recording process, or is it going to be a signal which is clean and proper and not cut from its top or bottom, but you hear it is distorted because it was distorted in the first place. Well I can't figure a way to put it in a better way... Or is the signal going to the speaker from the amp gonna be a cut one because it was cut from top and bottom during the recording process?

    I have for example The Best of the Doors Limited Edition. Produced by Warner Music Manufacturing Europe. Track 7, "five to one",it hass so much distortion that I can't even listen to it at moderate levels... Yes I am actually asking having in mind the damage factor. If I listen to it at a reasonably high level I have this distortion and is it gonna have the same effect with a clipping amp or is it still a proper signal carrying "distorted audio" ? That is what I am trying to find out. Thank you for your help.
     
  16. Ted Lee

    Ted Lee Lead Actor

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  17. Cagri

    Cagri Second Unit

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  18. Cees Alons

    Cees Alons Moderator
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    Cagri,

    Again: relax. Listening to a commercial CD will almost certainly not destroy your speakers.

    Now where I think you're wrong:
    I believe that you think that an amp can send a "full" signal (unclipped) to a speaker which sort of carries the distorted CD signal. Thus a distorted signal output by a non-clipping amp would still be harmless.
    But that's where your concept is wrong. The amp's signal does not "carry" the signal (like a radio wave does), but the amp simply outputs the signal itself, period. The signal is not contained in some way in the signal of the amp, it is the signal of the amp. The amp simply amplifies the original signal as exactly as it can and produces the power to have the voltages of the signal with enough current to produce, yes that POWER. [​IMG]
    If that signal was already deformed in the first place: it will produce the deformed signal. If the signal was fine, but for some reason the amp cannot reproduce a proper copy, it produces a a deformed version of the original signal. Both could look exactly the same (but don't have to, of course, because the type of deformation - distortion - could very well be different too).

    Hope this helps, but don't hesitate to ask on.

    Cees
     
  19. Cagri

    Cagri Second Unit

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    Cees,
     
  20. Vince Maskeeper

    Vince Maskeeper Producer

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    But I did explain. % of distortion, a small distorted signal is a mix of full wave forms vs. a full amplitude wave squared to 10% or more. I don't know how else to say it.

    -Vince
     

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