Logic Pro 9 Odd: negative-shifted waveform??

Pands

Logician
This is from a studio recording from 1989, done on an SSL. All-digital CD production. Maybe the AD converters weren't quite up to snuff yet at that point, or something? The entire waveform is shifted into negative territory, as you can see on the attached JPEGs.

Questions:
a) How would something like that happen?
b) What are the sonic ramifications? Will this SOUND different?
c) Can this be shifted back up to the center baseline somehow?

I've never come across anything like this, so I'd be curious if someone has any insight?

Cheers,
Peter
 

Attachments

That is called DC Offset. Some editing applications can remove it (recenter the main audio correctly), like Peak for example. I'm sure now that you know what it is you can find something to remove it.
 

Eli

Logician
Logic's own sample editor has a "remove DC Offset" function. I think it should do the trick.
 

michaelo

LUG Emeritus
Questions:
a) How would something like that happen?
b) What are the sonic ramifications? Will this SOUND different?
c) Can this be shifted back up to the center baseline somehow?
(a)A DC offset most commonly happens as a result of problems in the A/D converter or its subsystems. DC creeps into the signal so that the average sample value becomes non zero.
(b)Possible clicks and pops and significant loss of headroom
(c) As suggested, Logic can process and remove a DC offset
 

Pands

Logician
Thanks for all you guys' pointers! I'll have to look into those suggestions and see how audible the difference might turn out to be.

Grateful for your help!

Cheers,
Peter
 

Pands

Logician
Wow! Just as a quick follow-up: the difference is indeed noteworthy!

Doing the Change Gain/Search Maximum thing in Logic reveals that the song, the way it was mastered on the CD, with the wacky DC Offset, reached only a maximum of 48.67%, and it sounded really weak and thin. After applying the DC Offset, it now is at a full 100% and obviously sounds much stronger.

I always thought this song sounded meek and lifeless. Now, years later, I can see why, and it wasn't just my imagination!

Again, thanks a million for all your contributions!

Cheers,
Peter
 
Top