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After recording, waveform is shifted upward

Aug 15, 2012 7:07 PM

I am using Audition to record from phonograph using a honestech USB interface connected between. That's an important detail because recordings with a USB microphone, for instance, are perfectly normal.  The issue with this recording from turntable is that the waveform (upper part of screenshot) is getting translated/shifted upward by a few db, it seems.  Its not occurring to me what the remedy for this is.  I will make adjustments to the turntable, making sure its on a level surface,  play with tracking weight, etc., to see if that will help fix this.  Thanks in advance for any possible guidance.adobe-audition_shifted_upward_waveform.JPG

 
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  • Currently Being Moderated
    Aug 15, 2012 7:53 PM   in reply to JAKE JONSON

    Looks like you have some DC offset happening.  That's when some DC current gets mixed in with the AC audio signal and causes the zero point on your waveform to be offset upwards by a fraction of a volt.  It makes sense it's happening on your turntable since there are DC voltages floating around in there.

     

    Audition has a tool that corrects DC Offset.  On CS6 for some reason it's tucked away on the Effects/Amplitude and Compression/Normalise menu.  Just put a tick in the DC Offset Correction box (and untick the Normalise box if you don't want to change your levels) and it should fix it for you.

     
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  • SteveG(AudioMasters)
    5,591 posts
    Oct 26, 2006
    Currently Being Moderated
    Aug 16, 2012 2:24 AM   in reply to Bob Howes

    Bob's right, but I have to tell you that this is a huge shift - I don't ever recall seeing one that big before! The first thing you need to do before mucking about with the turntable though is to unplug the input to the interface from the phonograph (is it really a phonograph? - see below) and see if the shift is still there when you record, even though it will be silence you are recording. If it is, then don't bother with adjustments - just purchase a new interface, because that's where your fault is, and you won't be able to fix it.

     

    Why do you need a new one when Audition can potentially fix this, you might ask? Well, a 12dB offset is actually going to limit the maximum output you can get from the device, quite considerably - so you are losing headroom. This means that a heavily modulated recording is likely to run out of headroom, and clip. Not good. It indicates that the internal electronics really aren't up to much.

     

    This is a phonograph. Is it actually one of these you are using?

    http://upload.wikimedia.org/wikipedia/commons/thumb/a/a0/EdisonPhonograph.jpg/230px-EdisonPhonograph.jpg

     
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