DC Offset

[JackA]

First off, thanks for all the suggestions for Stereo Panning, I didn't know many tools were available in GW! Thank You!!

I made a crude drawing of DC Offset....
http://www.angelfire.com/empire/abpsp/dcoffset.gif

You might say I'm paranoid about DC Offset (constantly checking while enhancing audio; especially before Maximizing Volume). I have heard poor (non single point) grounding can cause DC Offset. I notice this a lot when people "rip" vinyl records to MP3, but that's more hardware related. In its worse case, I assume it can alter volume, and in the case of a power amplifier, speakers may receive a DC. It can be frequency dependent; I sometimes see this (in GW) at low frequencies (30Hz?); not sure that can actually be corrected. I haven't found anyone who has done extensive research on it, just best to avoid the offset.

I do know many alterations in GW can affect DC Offset, such as changing Dynamics, Peak Trimming, etc..
Though nothing severe, I do notice when I (sometimes) save to MP3, from .WAV or .FLAC, with NO offset, when I reopen the MP3 file there is offset. Maybe it's just a fact that MP3 compression (distortion) may be causing it? I think I'm using Lame 3.89 encoding. Are there superior encoders out there?

Thanks, Jack

[bido]

Jack,
I do a lot of vinyl "ripping" as you put it LOL. I have found that it is more so the turntable that is the culprit for the 30Hz noise. Do a test, I presume you are using a TTable and a mixer/pre-amp to provide the signal to your pc and in turn Gwave. First turn pc on start GW start recording on the channel that you are "ripping" vinyl from, is there the 30Hz signal?? if not turn on ur Pre-amp is the signal there now? If it is still clear turn ur Ttable on. If it becomes audioble then check your grounds. If they are all good then it may be the power supply in your turntable test this by connecting another device to the input. I have 2 turntables and one emits a noise due to the internal PSU also direct drive TT's are culprits of this although direct drive TT's generally get their noise from the PSU that is usually internal.

[JackA]

Jack,
I do a lot of vinyl "ripping" as you put it LOL. I have found that it is more so the turntable that is the culprit for the 30Hz noise. Do a test, I presume you are using a TTable and a mixer/pre-amp to provide the signal to your pc and in turn Gwave. First turn pc on start GW start recording on the channel that you are "ripping" vinyl from, is there the 30Hz signal?? if not turn on ur Pre-amp is the signal there now? If it is still clear turn ur Ttable on. If it becomes audioble then check your grounds. If they are all good then it may be the power supply in your turntable test this by connecting another device to the input. I have 2 turntables and one emits a noise due to the internal PSU also direct drive TT's are culprits of this although direct drive TT's generally get their noise from the PSU that is usually internal.

Bido, you're more than kind to help!! But it was others, not I, who were ripping vinyl (some material never made it to CD in stereo) just happened to notice the Offset!!

Used to love vinyl "audio", made my own preamp from Op Amps (was published in Hi Fi Magazine), from a published book about Op Amps. Was so neat to thank the author, Walter Jung, who I found on the internet!! Loved the Audio Technica, I think, AT440ML (Micro-Line) cartridge.

Hang around, maybe I'll rip a few LPs I bought, someday!!!

Thanks, again!

Best - Jack

[DougDbug]

I made a crude drawing of DC Offset....
http://www.angelfire.com/empire/abpsp/dcoffset.gif

Asymmetry isn't exactly the same as DC offset. Some sounds are legitimately asymmetrical. True DC offset will show-up during silence.

IIRC, GoldWave's old offset correction would sometimes introduce a DC offset by trying to make the waveform symmetrical (with an average of zero). Then, you'd get a "click" at the beginning & ending of the track where the silence was offset. I think this has been fixed.

A high-pass filter at 20Hz or lower will remove any true DC (since DC is zero Hz) and it may make your waveforms more symmetrical. But every single wave may not have equal positive & negative amplitudes.

[JackA]

I made a crude drawing of DC Offset....
http://www.angelfire.com/empire/abpsp/dcoffset.gif

Asymmetry isn't exactly the same as DC offset. Some sounds are legitimately asymmetrical. True DC offset will show-up during silence.

IIRC, GoldWave's old offset correction would sometimes introduce a DC offset by trying to make the waveform symmetrical (with an average of zero). Then, you'd get a "click" at the beginning & ending of the track where the silence was offset. I think this has been fixed.

A high-pass filter at 20Hz or lower will remove any true DC (since DC is zero Hz) and it may make your waveforms more symmetrical. But every single wave may not have equal positive & negative amplitudes.

Thanks, Doug, think I tried that. Not a big problem, just wonder how it gets there. Like on a Zeppelin "boot" song, the waveform is so bad, there's no easy or good way to correct it. If you split any song in half, for example, an offset generally surfaces. Probably no such thing as absolutely no offset.

Best, Jack