Waveform not centred

[Melvyn]

Hi,

I have Ubuntu Hardy Heron and Audacity 1.3.4.
I'm recording my vinyl record to copy them onto CDs. Today I noticed something that had never happened before: Normally waveforms are centred on the zero line of the dB scale. Well, now, although the right channel is centred, the left one is slightly above the zero line. How does this impact on the sound quality? And how do you fix it (i.e., lower the waveform so it "huggs" the 0 dB line?

[Gale Andrews]

Hi,

I have Ubuntu Hardy Heron and Audacity 1.3.4.
I'm recording my vinyl record to copy them onto CDs. Today I noticed something that had never happened before: Normally waveforms are centred on the zero line of the dB scale. Well, now, although the right channel is centred, the left one is slightly above the zero line. How does this impact on the sound quality? And how do you fix it (i.e., lower the waveform so it "huggs" the 0 dB line?

It's known as DC offset. It can cause inaudible low level distortion (which becomes audible when filters/effects are applied or if the sound is compressed, for example in MP3 export). It can also cause audible clicks at start and end when played back (even without editing). Fix it by

* clicking on the Track Panel by the mute/solo buttons > Split Stereo Track
* click on the Track Panel of the left channel then Effect > Normalize and check the Remove DC Offset box > OK.

Look into fixing the sound device you are recording into/pre-amplifier/recording device you are using as appropriate.

Gale

[Melvyn]

Many thanks Gale. That solved it.

Melvyn