DC Offset

Chester01 · May 24, 2004, 12:57 AM

Today, I found a plugin on http://www.electricstart.de called DC Offset. From a little research I hve tried to piece together what this plugin does. It seems to me that when audio is compressed, it is in a linear "step" fassion, not sine waves (what most sound waves are) when un-compressing, the equilibrium of the sine wave can be messed up (not at 0) which can lead to clipping and such. Is this true? Does any one know about how this plugin works? Is it beneficial to audio quality? I have noticed less "clicks" and distortion while using it... I have noticed it sets me at -68 decibles when I have no audio signal running through the card instead of -Inf (Infinate)... Any help on this matter would be appreciated! Thanks!

Nappylady · May 24, 2004, 06:33 AM

I would be VERY careful with anything that says "DC Offset". When you get into amplifier design, you learn that any DC offset should be avoided at any cost--it will cause current to flow through your output transistors even when silent, and if too high, can reduce the power handling of your speakers, or even destroy them.

I'd suggest looking at the output of the plugin in Goldwave or CoolEdit or some other high-end audio software, and checking to see if it adds a DC offset. If it does, I'd recommend against using the plugin, ever, because it could be very dangerous.

Good luck!

meroveus · May 24, 2004, 07:39 AM

That is true nappylady.

The problem is that Creative cards, and especially the Live, seem to add DC of their own accord to the signal.

So when i record something thru the line-in, I have to go into Wavelab and do the 'remove DC-offset' thingy.
Is there some mod perhaps to adjust the DC-offset of your card, by using high precision trimmer caps or something?

Would you know anything about this, TravelRec?

**dj_stick** · May 24, 2004, 08:35 AM

http://www.hardwareheaven.com/showthre...threadid=46307

meroveus · May 24, 2004, 10:34 AM

Thanks dj_stick, but I've seen this post. It has nothing for me.

It is just a lame mod where some components are replaced with others which are supposedly better.

You see this thing all the time, with lamers on forums replacing their caps and opamps and proclaiming miracles in clearer sound. The problem is, they never back up their results with science.
No RMAA tests are ever done afterwards, so you can be sure all the improvements are solely in the modder's mind.

Instead, I was hoping that someone with genuine electronic knowledge such as TravelRec could point me out a small mod to measure and then adjust the DC offset. It should be just a matter of inserting a trimmer cap or variable resistor. (But then what would i know?

)

Chester01 · May 24, 2004, 12:53 PM

Thanks for your help guys, well the people who stayed on topic... The plugin does have an "amount" control which i noticed directly relates to the "noise" I was experiencing with no audio running through the line. Should i set the DC offset at like 25% or something like that? It only adds +4 db of noise from -Inf when used 100%.

**dj_stick** · May 24, 2004, 12:58 PM

hmm well i think travelrec should be able to answer both questions posed here (As the plugin was on travelrec's site and travelrec is an audio-electronic genious)

Chester01 · May 24, 2004, 01:04 PM

I have also been lookin around a bit and it seems that ANY sort of gain or basically any plugin that modifies the signal in ANY way is going to add a bit of noise to the signal especially when looking at the signal with no audio running through the card. Not that i can HEAR the noise but its still there...

**dj_stick** · May 24, 2004, 01:05 PM

any gain effect will amplify the entire singal, including the inherent noise floor, its not reall adding as such, just increasing the gain

Chester01 · May 24, 2004, 01:18 PM

Here: this one gives me -108 db noise:** FXBusX-Stereo Decimator-DC Offset-Epilog ** (DC offset at 1%) This is primarily for audio listening and such but I read about dc offset being good for speakers because they can correct distortion caused by audio compression (I download mp3's and such)... If someone has opinions on this setup, please give them, till this point I have been using the DSP on my own without much if any council on what works best. Thanks!

**dj_stick** · May 24, 2004, 01:36 PM

there are two types of audio compression - acoustical used when producing music - ie compressor plugins in the DSP and then there is the mp3/wma type compression… not sure which one the distortion would apply to tho

TravelRec. · May 24, 2004, 02:13 PM

Hi!

I´m late, I know...
The plugin on my side is from a guy who sent it to me few month ago. I´ve tested is sometimes but I don´t really need it, ´cause I have no probs with DC-offset and Audigy-card (DC-Offset is below 0.5% and that´s okay for me). AND: I don´t think that some DC-Offset is very dangerous for speakers; the name is saying it: DC, so the current flows in one direction. Since all outputs of the soundcard are decoupled over a capacitor and all amplifiers have capacitors in the input stage, such a DC cannot flow directly to the speakers and damage them. All what the speaker is getting is AC. The only real reason to kill DC-offset is to get silence while mixing and cutting audio-tracks with different offsets that can cause some scratching or cracking sounds at the cut-edges. So don´t fear to blow your speakers with DC, AC in high frequencies and high levels is much more dangerous.

BTW: the electronic A/D application I made with the CS5331-A produces 0% DC due to a filter stage inside the A/D chip.

Greetings!

TravelRec.

Chester01 · May 25, 2004, 12:41 AM

Thanks this clears things up quite nicely!

May 24, 2004, 12:57 AM	#1
Chester01 HardwareHeaven Senior Member Join Date: Jan 2004 Location: St. Cloud, MN Posts: 492 Rep Power: 0	DC Offset Today, I found a plugin on http://www.electricstart.de called DC Offset. From a little research I hve tried to piece together what this plugin does. It seems to me that when audio is compressed, it is in a linear "step" fassion, not sine waves (what most sound waves are) when un-compressing, the equilibrium of the sine wave can be messed up (not at 0) which can lead to clipping and such. Is this true? Does any one know about how this plugin works? Is it beneficial to audio quality? I have noticed less "clicks" and distortion while using it... I have noticed it sets me at -68 decibles when I have no audio signal running through the card instead of -Inf (Infinate)... Any help on this matter would be appreciated! Thanks!

May 24, 2004, 12:53 PM	Thread Starter #6
Chester01 HardwareHeaven Senior Member Join Date: Jan 2004 Location: St. Cloud, MN Posts: 492 Rep Power: 0	Thanks for your help guys, well the people who stayed on topic... The plugin does have an "amount" control which i noticed directly relates to the "noise" I was experiencing with no audio running through the line. Should i set the DC offset at like 25% or something like that? It only adds +4 db of noise from -Inf when used 100%. __________________ COMP: Dual Intel PIII 733 Mhz; GeForce 4 Ti 4600; 1.128 Gb RAM; SB0350 (Audigy 2 ZS Platnium) STEREO(I UPGRADED):Crown Audio K1 and K2 amplifiers (4000 watts at .1% THD ), JL 13w7 Subwoofer (6.5 CF) (2) 18" PR's, Klipsch SB-1's, some cement blocks for speaker stands...

May 24, 2004, 01:04 PM	Thread Starter #8
Chester01 HardwareHeaven Senior Member Join Date: Jan 2004 Location: St. Cloud, MN Posts: 492 Rep Power: 0	I have also been lookin around a bit and it seems that ANY sort of gain or basically any plugin that modifies the signal in ANY way is going to add a bit of noise to the signal especially when looking at the signal with no audio running through the card. Not that i can HEAR the noise but its still there... __________________ COMP: Dual Intel PIII 733 Mhz; GeForce 4 Ti 4600; 1.128 Gb RAM; SB0350 (Audigy 2 ZS Platnium) STEREO(I UPGRADED):Crown Audio K1 and K2 amplifiers (4000 watts at .1% THD ), JL 13w7 Subwoofer (6.5 CF) (2) 18" PR's, Klipsch SB-1's, some cement blocks for speaker stands...

May 24, 2004, 01:18 PM	Thread Starter #10
Chester01 HardwareHeaven Senior Member Join Date: Jan 2004 Location: St. Cloud, MN Posts: 492 Rep Power: 0	New DSP Setup Here: this one gives me -108 db noise: FXBusX-Stereo Decimator-DC Offset-Epilog (DC offset at 1%) This is primarily for audio listening and such but I read about dc offset being good for speakers because they can correct distortion caused by audio compression (I download mp3's and such)... If someone has opinions on this setup, please give them, till this point I have been using the DSP on my own without much if any council on what works best. Thanks! __________________ COMP: Dual Intel PIII 733 Mhz; GeForce 4 Ti 4600; 1.128 Gb RAM; SB0350 (Audigy 2 ZS Platnium) STEREO(I UPGRADED):Crown Audio K1 and K2 amplifiers (4000 watts at .1% THD ), JL 13w7 Subwoofer (6.5 CF) (2) 18" PR's, Klipsch SB-1's, some cement blocks for speaker stands...

May 24, 2004, 02:13 PM	#12
TravelRec. Alternative Audioproductions Join Date: Sep 2003 Location: Germany / Sachsen-Anhalt Posts: 1,710 Rep Power: 56	Hi! I´m late, I know... The plugin on my side is from a guy who sent it to me few month ago. I´ve tested is sometimes but I don´t really need it, ´cause I have no probs with DC-offset and Audigy-card (DC-Offset is below 0.5% and that´s okay for me). AND: I don´t think that some DC-Offset is very dangerous for speakers; the name is saying it: DC, so the current flows in one direction. Since all outputs of the soundcard are decoupled over a capacitor and all amplifiers have capacitors in the input stage, such a DC cannot flow directly to the speakers and damage them. All what the speaker is getting is AC. The only real reason to kill DC-offset is to get silence while mixing and cutting audio-tracks with different offsets that can cause some scratching or cracking sounds at the cut-edges. So don´t fear to blow your speakers with DC, AC in high frequencies and high levels is much more dangerous. BTW: the electronic A/D application I made with the CS5331-A produces 0% DC due to a filter stage inside the A/D chip. Greetings! TravelRec. __________________ Always take a look behind.

May 24, 2004, 06:33 AM	#2
Nappylady DriverHeaven Addict Join Date: Jun 2003 Posts: 257 Rep Power: 0	I would be VERY careful with anything that says "DC Offset". When you get into amplifier design, you learn that any DC offset should be avoided at any cost--it will cause current to flow through your output transistors even when silent, and if too high, can reduce the power handling of your speakers, or even destroy them. I'd suggest looking at the output of the plugin in Goldwave or CoolEdit or some other high-end audio software, and checking to see if it adds a DC offset. If it does, I'd recommend against using the plugin, ever, because it could be very dangerous. Good luck!

May 24, 2004, 07:39 AM	#3
meroveus DriverHeaven Junior Member Join Date: Jul 2002 Posts: 63 Rep Power: 0	That is true nappylady. The problem is that Creative cards, and especially the Live, seem to add DC of their own accord to the signal. So when i record something thru the line-in, I have to go into Wavelab and do the 'remove DC-offset' thingy. Is there some mod perhaps to adjust the DC-offset of your card, by using high precision trimmer caps or something? Would you know anything about this, TravelRec?

May 24, 2004, 10:34 AM	#5
meroveus DriverHeaven Junior Member Join Date: Jul 2002 Posts: 63 Rep Power: 0	Thanks dj_stick, but I've seen this post. It has nothing for me. It is just a lame mod where some components are replaced with others which are supposedly better. You see this thing all the time, with lamers on forums replacing their caps and opamps and proclaiming miracles in clearer sound. The problem is, they never back up their results with science. No RMAA tests are ever done afterwards, so you can be sure all the improvements are solely in the modder's mind. Instead, I was hoping that someone with genuine electronic knowledge such as TravelRec could point me out a small mod to measure and then adjust the DC offset. It should be just a matter of inserting a trimmer cap or variable resistor. (But then what would i know? )

May 25, 2004, 12:41 AM	Thread Starter #13
Chester01 HardwareHeaven Senior Member Join Date: Jan 2004 Location: St. Cloud, MN Posts: 492 Rep Power: 0	Thanks this clears things up quite nicely! __________________ COMP: Dual Intel PIII 733 Mhz; GeForce 4 Ti 4600; 1.128 Gb RAM; SB0350 (Audigy 2 ZS Platnium) STEREO(I UPGRADED):Crown Audio K1 and K2 amplifiers (4000 watts at .1% THD ), JL 13w7 Subwoofer (6.5 CF) (2) 18" PR's, Klipsch SB-1's, some cement blocks for speaker stands...