Clipping Questions

These questions have been bugging for awhile but I just didn't want to show my ignorance I gues. I’ve finally broken down and am asking!

Questions:
1) From what I understand, going into the “red” on a meter doesn’t actually sound bad; it's only when the audio clips (i.e., hits the top of the meter) is there a negative effect. Is this correct?

2) From what I understand, clipping (i.e. going in the red) on a bus to which several audio tracks have been sent doesn’t have a negative effect on the sound. Is this correct?

Thanks!

I'm no expert but I'll try to add something to DonnyAir's excellent comments. And of course all of this discussion is assuming digital clipping since analog clipping acts quite differently.

To me "clipping" has nothing to do with what the meters say. Going into the red is going into the red. The result might or might not be clipped. Clipping is when the digital signal bangs up against 0db so that the waveform peaks get flattened. The peaks are flattened because the recorded signal can't actually go "over" 0db. You can easily see clipping with an audio editor and typically you can very easily hear it -- it's nasty!

It's OK for the signal to peak at 0db which is what you get if you normalize to 100%. That's a hot signal but with no flat peaks. Well, actually I've seen some issues with signals normalized to 100% That is, when played back with the Windows Media Player with SRS processing ON it sounded like the processed signal was clipping. So now I always normalize to a few db below 0db to leave room for SRS or other processing. This might just be an issue with WMP though. But I've digressed....

I once had a soundcard with some kind of problem where the recorded signal was being clipped (peaks with flat tops) at a level way below 0db. So even though the sound was not loud it certainly was awful!

--Larry

ORIGINAL: larrymcg

...So now I always normalize to a few db below 0db to leave room for SRS or other processing. This might just be an issue with WMP though. But I've digressed....

I'm of the opinion that "normalizing" should only be considered as a last resort on tracks that can't be re-recorded...Even so, if extreme clipping and/or digital distortion has already occurred, normalizing isn't going to clean it up--it's only going to lower the overall volume level of the offensive peaks...Please read on:

ORIGINAL: DonnyAir

And, you should always consider gain structure. It's an often overlooked parameter in audio...both digital and analog. If you are driving an input on a pre too hard, in relation to it's output, distortion can occur whether you actually clip the input of the card or not, although there have been times when certain people have found this desireable...

Donny is so correct on this one...This was much more critical, in some ways, in the old analog days (signal-to-noise ratios, tape hiss, etc.,...) but it is still relevant to the digital software that we use...Even though we no longer have to worry about overcoming tape hiss by recording tracks as "hot" as possible, we must still be aware of gain structure in the signal chain because improper settings affect the final product as a whole...

Example: If you're using a mic preamp with the input level set too low, you'll have to crank up the output gain to achieve a workable signal level to feed into your mixer...Not only does this introduce unnecessary noise, it's going to affect the sonic quality of your preamp's output...(As Donny pointed out, sometimes the respective settings are intentionally set improperly in order to achieve a "desired" sound, but more often than not it is desirable to trim your settings properly)...

I've posted several replies to various threads about my recording techniques...In a nutshell this is what I basically try to do:

1) Get my individual tracks recorded somewhere between -6dB to -9dB (we're in the digital domain...we don't have to worry about tape saturation or noise factors);

2) Use as little processing as possible (unless I'm shooting for a desired sound quality) on the individual tracks while I'm laying them down;

3) At the mix stage--other than vocal effects--I use subtle boosts/cuts in EQ and fader level (in addition to panning) to get the individual parts to sit well in the mix...As a general rule, I try to avoid any excessive dynamic processing (depending on the song) that could influence the overall final mix when it's time to master;

4) I try to get my mixes to sound "mastered" but not by worrying about "perceived loudness"...My mixes usually peak around -3dB which leaves a reasonable amount of headroom to be "played with" at the mastering stage;

Hope this information is somewhat helpful!

ORIGINAL: barthowk

Thanks for the replies guys. I'm still not clear on my original questions though, and now have an additional!

1) Is the definition of "clipping" just going into the red and "overs" hitting 0db? (my other questions assume this is a correct statement)
2) Is it okay to "go in the red" on a DAW track, as long as there are no overs?
3) Is it okay to clip and have overs on a bus to which several tracks have been sent?

BTW, I'm using SONAR.

It depends on if the meters are accurate and if "red" means you have already clipped or you are about to. I'm thinking on a digital system it means you have already clipped and it's too late. The only way to verify is to open the clip in sound forge and use the find clipped wavforms feature or just zoom in and view the waveform to do a visual confirmation. If you zoom into the sample level and you see it's only two samples at the top with a tiny flat line between them that's not the end of the world but if it's more and you can hear distrotion with headphones the clip it blown.

However, in sound forge you can use the pencil tool to fix the clipped peaks if there are not too many of them. You just have to reduce by 2db to give yourself room to draw up. I think Sony also has a plugin that will do it for you but it's touchy. You can only fix a small selection at a time or it goes crazy. But that's a normal de-clipping job anyway if it's the whole track it's toast. The only reason I know abou the bug is that I was trying to fix a rip of Rush - Vapor Trails.. if the plugin could have laughed at me it would have...LOL !

When Sonar indicated that something is in the red and over 0DB Sonar is lying.

Well not really. Sonar keeps it in floating point internally so it will not sound bad unless it is still over 0 db at the final output.

You can boost a signal well above 0Db at a send and then reduce it below 0DB and you will not creat unpleasantries. When dealing with floating point math you do not clip until you get to the output.

ORIGINAL: Dana DeBoer

Is there a reason not to record as close to 0db as possible?

Quite simply because you don't have to...In the digital realm you needn't concern yourself about tape hiss and noise factors from plugins (unless you're using a lot of outboard gear)...Why risk getting close to the clipping stage when it isn't necessary? By recording at a lower level you leave your tracks plenty of headroom and, in the end, room for your mix to "breathe" dynamically...

ORIGINAL: papa2004

ORIGINAL: Dana DeBoer

Is there a reason not to record as close to 0db as possible?

Quite simply because you don't have to...In the digital realm you needn't concern yourself about tape hiss and noise factors from plugins (unless you're using a lot of outboard gear)...Why risk getting close to the clipping stage when it isn't necessary? By recording at a lower level you leave your tracks plenty of headroom and, in the end, room for your mix to "breathe" dynamically...

Doesnt turning up faders cause hiss? I know on my mixer, if i have nothing playing, and turn my fader up that i get an audible hiss.
Sooo... It would seem to me, that if i record as close to 0db as possible, I would need to turn my fader up that much less in the mix. Thus less hiss being introduced into the mix.

What am i missing here?

dana

My sound card is a tascam us 428.
My board is a AH Mixwiz 16:2
When I hear this noise it is on a channel that has my sound cards outs running into it. With nothing playing. I generally have the tascam volume riding about 25%, the track volume aproximately -18 - -12db, and if i turn the master faders up reaching 0db i start hearing a hiss. I have also heard this hiss on my friends mackie which is probably an open circuit. Im going to do some further testing on my AH to see what a closed circuit will do.

I really wasnt trying to trouble shoot my system. but... since there are boards and sound cards that arent whisper quite are you going to introduce more noise into your mix if you record near 0db, if you have an inferior component?

dana

Donny,

I will indeed go and check things out abit more. This mixer I have had awesome reviews for having good preamps. So I would assume that if you have a good preamp it is necessarily going to be a quite preamp.
I actually was surprised to hear this hiss coming form them. My guess is it's probably from my tascam. I will get back with you on that after a bit of fooling.

dana