Funky looking waveforms

[tommyd]

Has anyone ever seen a waveform ( in this case in Protools) were the top or bottom half looks normal but the opposite side is a "flat line" if you will? I've seen this a couple of times and never bothered to ask why. In all instances ( now that I think of it loudly tracked guitars) the track sounded fine. Any ideas?
TommyD

[JonCraig]

could be (and this is a long shot...) that one side of a push-pull amp stage is blown. in class ab amps, one transistor (or tube, or whatever) conducts one half of the wave, while another transistor, tube, etc. conducts the other half. could be the onboard pre of a condensor, or the mic pre, or a compressor, or eq, etc.--anything with a gain stage. if one were blown, though, i'd think it would sound poopy... but who knows.

if you ever notice it while tracking (and you've got the time to spare) try swapping out different parts of the chain and see what effect that has on the waveform. just out of morbid curiosity.

and someone with more sense than me will likely reply here and say, "yes. that's normal in the case of _____," and i'll really look stupid.

--jon

[tommyd]

Actually your on the same train of thought that I am. Since the recording sounded o.k. I'm assuming that it wasn't a software issue, but something in the chain from the mic up to and including the converter. Unfortunately I've never noticed this until awhile after it's happened and haven't been able to trouble shoot this methodically. I'll be interested to find out the scoop on this.
Tommy

[beechstudio]

Check out this thread. I think maybe this is a related issue.

http://gearslutz.com/board/showthread.php3?t=32108

[Gregg Sartiano]

Had it happen with an A.R.T. Tube MP mic pre -- knowing what (little) I know, looks like one side of the push-pull would clip waaaaaaaaaaay too soon. I dunno what was wrong with it.

Also, certain analog synth sounds come out this way -- it's just a part of the synthesis and filtering.

Watch out with those "loudly tracked guitar" sounds -- tracking nuances that seem small when recording have a way of sneaking up on you during mixing -- you're dealing with an already clipped signal, so translating that raw power to a finished CD is a game of inches, so to speak.

[JonCraig]

would guitar tracks have the same problem as the kick drum described in that thread, though? a guitar's strings certainly oscillate very well. i'm curious, though. the original poster said in each instance, the source was "loudly tracked guitars". would these have been overdriven guitars, perhaps? maybe a pedal (or solid-state distortion in amp) does some sort of asymetrical clipping to get its sound?

just a few thoughts.

--jon

[tommyd]

Originally Posted by JonCraig

would guitar tracks have the same problem as the kick drum described in that thread, though? a guitar's strings certainly oscillate very well. i'm curious, though. the original poster said in each instance, the source was "loudly tracked guitars". would these have been overdriven guitars, perhaps? maybe a pedal (or solid-state distortion in amp) does some sort of asymetrical clipping to get its sound?

just a few thoughts.

--jon

Yep, I did say guitar tracks. FUnny thing is, what prompted me to post this was a phone call from a producer that I work with. He's tracking in Santa Barbara (without me ) and saw this very problem on, you guessed it, the kick drum track. He called and reminded me of when we'd seen it before and asked if I ever found out the cause. And so the reason for this thread.
TommyD

[2leod]

I've had it once on a kik during a live recording. I just put it down to mic placement, where the diaphragm was fighting a standing wave...

[drmmrboy]

Originally Posted by tommyd

and saw this very problem on, you guessed it, the kick drum track.

I've had it on kick before. (only on kick) Changed the cable, pre, and in the process, the mic got moved a bit....
So, problem solved, but I don't know what the problem was....

Andrew

[theblue1]

My first thought was bad zero offset but I looked at the screen shot in that other thread and I ain't so sure...

[Winey]

I've seen it on Bass, Kick and Snare.
I've had the waveform look weird on Bass, then a different player grabs the bass and the waveform is suddenly normal!
Must have something to do with how the string is plucked (polarity issue).

[cebolao]

saxophone

[Reptil]

Originally Posted by Winey

I've seen it on Bass, Kick and Snare.
I've had the waveform look weird on Bass, then a different player grabs the bass and the waveform is suddenly normal!
Must have something to do with how the string is plucked (polarity issue).

it is. how the string is played (attack), makes the sinussoide. (in simple terms, does the waveform go "up" first (when it is plucked, so most energy is there), so, positive, or "down")
I think it is better explained in that other thread, mentioned in this thread...
lotsa analogue components in my doepfer can only work with "positive". As it is all voltages; positive voltages.. there's where rectifiers come in to play.. lotsa weird waveforms here.

[Improv]

Could be a bad amp, cable, or somesuch. But certain kinds of distortion (on guitars) will create a rectified waveform. I've seen it with (usually improperly set) compressors.

It's very apparent on brass though. Almost no negative acoustic energy... never understood why.

[Rail Jon Rogut]

Make sure you don't have the option in your prefs set for the waveform to be drawn rectified.

Rail