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A question about DC Offset

DC Offset

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#1 Garrett Wang

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Posted 03 March 2017 - 02:46

I know that DC offset is amplitude displacement from zero and it can be seen as an offset of the waveform from the center zero point. I know that it can can cause unwanted clicks, distortion and loss of audio volume, but my question is as follows:

 

Why do wonky DC offset problems happen in recordings? Is it from adjusting a recording from stereo to mono?



#2 Mastrcode

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Posted 09 March 2017 - 01:41

It mostly happens with analog gear (hardware synths, microphone pre-amps) or A/D conversion, caused by small faults in the electrical circuit. But also software can cause DC offset. A VST plugin, which simulates or reproduces analog signal flow can also cause DC offset, or even delay plugins, if the delayed signal interferes with the original signal, when used long feedbacks. Then it can happen, that the delayed signal overlays the original sound and then DC offset can happen.

You can prevent DC offset by using a HP filter around 10 - 20 Hz at the end of the signal chain. This removes DC offset.


Edited by Mastrcode, 09 March 2017 - 01:44.


#3 OopsIFly

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Posted 09 March 2017 - 02:15

Renoise has a dedicated DC offset effect. It can provide synthetic DC offset, so you can make your own recordings crappy by demand. It can be very useful for certain effects, though it is not as good in removing dc than the butterworth n8 highpass filter. But you will want to remove it on the master with an hp filter though as not loose dynamic range or make people fear for their speakers...

 

Normally I always thought most of those samples with wobbling dc came from people recording wonky turntables?


Edited by OopsIFly, 09 March 2017 - 02:16.


#4 Mastrcode

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Posted 09 March 2017 - 09:55

Normally I always thought most of those samples with wobbling dc came from people recording wonky turntables?

This could also be a reason. Most of the old turntables have to be grounded with a separate cable to the amp on which they're connected. If they're not grounded, this can cause noises, hum, and also DC offset.



#5 ffx

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Posted 09 March 2017 - 10:27

Renoise has a dedicated DC offset effect. It can provide synthetic DC offset, so you can make your own recordings crappy by demand. It can be very useful for certain effects, though it is not as good in removing dc than the butterworth n8 highpass filter. But you will want to remove it on the master with an hp filter though as not loose dynamic range or make people fear for their speakers...
 
Normally I always thought most of those samples with wobbling dc came from people recording wonky turntables?


I wonder that some synths seems to generate DC offset by purpose. So what kind of certain effects do you mean? Also regarding the speakers, isn't a DC offset quite harmful?

#6 Mastrcode

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Posted 09 March 2017 - 19:00

I wonder that some synths seems to generate DC offset by purpose. So what kind of certain effects do you mean? Also regarding the speakers, isn't a DC offset quite harmful?

 

It can be very useful for certain effects

 

In some cases DC offset really can be an advantage, e.g.  a distortion effect can benefit from it. Best example is the Clip Distortion plugin of Apple's Logic DAW. It has a function called "symmetry". This symmetry shifts the audio signal "up/down" around the zero point (center line) in a certain way. So the symmetry is also a kind of DC offset effect, which can be a big advantage for distorting the signal. All the big hardstyle producers swear by it. Because this symmetry feature only makes it possible to create the right distortion for a good hardstyle kick.


Edited by Mastrcode, 09 March 2017 - 19:00.

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#7 OopsIFly

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Posted 09 March 2017 - 21:05

yes, exactly

 

asymmetric distortion transfer functions will generate even order harmonics to some extent, while pure symmetric will only generate odd. you can make a symmetric transfer function asym by dc shifting the input. just not forget to cope with the dc shift after the operation (hp filter the result), or you mess up your mix badly. I have a pure native doofer playing with this via the dc device, can sound a bit like a classic fuzz face - very gritty. might upload it one day.


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#8 Mastrcode

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Posted 09 March 2017 - 21:33

@ OoopsIFly, your interests info sounds funny. Are you from Germany? Klappt aber nur, wenn man barfuss läuft... :D



#9 OopsIFly

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Posted 11 March 2017 - 19:02

schau dir taktik's interessen an, und du verstehst warum... :smashed: