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I just tried this crazy experiment, and I need help understanding the results.

Here's what I did:

1. I turned up the final output volume in my mastering chain so loud that it created very noticable digital clipping in the loud sections of the song. I exported this song.

2. I then exported a quieter version with no digital clipping.

3. I import them both into a tracking program.

4. I invert the phase on the loud version and adjust the levels until all the shared sounds are phase cancelled, which leaves me with just the digital clipping sound.

5. I then invert the phase of the digital clipping and add it back to the super loud clipped version.

7. The clipping sound from the loud version is gone, but both clean and distortion-cancelled versions sound almost identical.

I was hoping that my distortion-cancelled version would sound much louder than the clean version, but without the distortion. Can anyone explain to me why this didn't occcur?

Also, can someone try to emulate my experiment to make sure I did everything right?

Comments

hueseph Sun, 12/18/2005 - 19:38

7. The clipping sound from the loud version is gone, but both clean and distortion-cancelled versions sound almost identical.

I was hoping that my distortion-cancelled version would sound much louder than the clean version, but without the distortion. Can anyone explain to me why this didn't occcur?

Not sure what you are comparing this too but I'm taking a stab that you are thinking it might work like a humbucking pickup which tends to have more power than a single coil. Of course this is not because there is phase cancellation but because there are two pickups. Hence, twice the power.

anonymous Sun, 12/18/2005 - 19:48

I should clarify the loudness aspect. I normalized both the clean version and the loud version, and they both ended up with the same volume. I had hoped that the loud version would normalize louder because the peaks were chopped off (which caused distortion, but then this distortion was removed). Did I somehow add back those peaks when I phase-cancelled the clipping distortion?

Michael Fossenkemper Sun, 12/18/2005 - 20:03

yes you did. compression, limiting, and clipping are non linear process's. The difference is exactly that, the difference. what you are getting is not quite the same thing but very close. It's easy to confuse these things. Although you are starting to think in a direction that will get better results. Questioning things and experimenting gets you closer to the result. You did everything right in your theory, the problem is that your theory was wrong.

The only clipper that I've heard that reduced the effect of clipping to an acceptable level is the omnia. At $12,000 it should do some things well, clipping artifacts was one of them, but only to a certain degree, and this wasn't near the levels of some of the louder CD's out there.

anonymous Tue, 12/20/2005 - 18:32

In case you all are curious, here are the files in mp3 (short fragment of the song):

The original material: [="http://www.headchemists.com/ro/cowboy_original.mp3"]Original[/]="http://www.headchem…"]Original[/]

The same file will the volume turned up so it clips: [[url=http://="http://www.headchem…"]Loud Distorted[/]="http://www.headchem…"]Loud Distorted[/]

The difference between the two extracted by inverting the phase of one of them: [="http://www.headchemists.com/ro/cowboy_distortion_isolated.mp3"]Distortion Isolated[/]="http://www.headchem…"]Distortion Isolated[/]

This clipping sounds like a lot of high frequency energy - what frequencies are most common in digital clipping?

Finally, the loud distorted version played with the isolated distortion (inverted) to cancel out the clipping: [[url=http://="http://www.headchem…"]Distortion Removed[/]="http://www.headchem…"]Distortion Removed[/]

Interesting, but I'm not sure there's anything useful here - just a demonstration of the laws of physics. According to the iTunes Sound Check, the original file is about 3 dB louder than the distortion removed file, but I don't know how to measure this accurately.

RemyRAD Tue, 12/20/2005 - 20:24

Headchem, the reason why your original is 3db louder, is because you flipped phase and combined both files, causing overall cancellation. It is like an operational amplifier, or Op-Amp circuit. It's the same principle. No negative feedback = hi again but more open sounding. Lots of negative feedback = low gain and a slightly more squeezed sound. (In real recording consoles this was a factor on the character of the sound. If you wanted a more open, upfront sound, you cranked microphone gain as much as you can get away with, before distortion, unless that's what you wanted. If you wanted a more smoother sound, you would crank microphone preamp gain down and push your fader higher. You would also get more headroom that way. But in mixers like the Mackies, they actually have a fixed gain microphone preamplifier and then an intermediate amplifier after that for actual gain control. That's why they generally sound somewhat consistent, regardless of gain setting.

You have simply reduced overall gain by your slight difference in level matching and probably due to the amount of overload which prevented gain from getting higher in your distorted version. Similar to the technique used in saturation of analog tape but certainly not the same results (that's why we don't do that in digital). Analog tape is nonlinear. Digital is linear. So your distortion in analog tape can be thought of as musical and due to its nonlinear 2nd harmonic components, similar to tube saturation, which is heavily more 2nd harmonic components and your distortion in linear digital can be considered, generally symmetrically clipped, third harmonic, unmusical, as 3rd harmonics do not occur naturally in real life.

But experimentation is always fun and you always learn something.

Happy Harmonics!
Ms. Remy Ann David

anonymous Mon, 12/26/2005 - 19:34

Falken wrote: your before and after sound the same because they are the same.

this is what you basically did:

B - (B - A) = A

Once you enter "non-linear land" that wont work! x^y is the problem.

The interested can go here:

Link removed

"beginners search"

type "Robert Orban" as inventor

You can see several approaches to a distortion cancelled limiter.

DC

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