Digital Audio, The Cure for Noise?

Home / the12volt's Install Bay / Car Audio / Digital Audio, The Cure for Noise? (

Topic Closed)

Welcome Guest :)

Members

Next Page > < Prev Topic Next Topic >

SiDogg

Copper - Posts: 65

Joined: July 02, 2002

Posted: March 31, 2005 at 11:20 PM / IP Logged

Forget about WHERE a noise is coming from for a moment, let's say it is there and there is nothing you can do about it.

How do you get rid of it?

Can you get rid of it by reading digital music, such as MP3s or a CD, into a device which has digital output (S/PDIF), to a Digital DSP (5.1 decoder) to the amplifier via RCA cables?

Does this make sense? Noise comes from an echo or extra voltage on the wire, right? So if the source is clean and the device reading the source reads digital format and does no ADC conversion, and outputs digitally to a non-noise-infected source, such as a high-end digital DSP, then there is no way for noise to get into the system, right??

deocder

Copper - Posts: 138

Joined: December 27, 2004

Posted: April 01, 2005 at 2:05 AM / IP Logged

Damn dude! You think to much!

Actually you got me thinking....

Lets try to figure this out.....

Crap, I cant do it.....too tired.. Digital Audio, The Cure for Noise? -- posted image.

But I am curious...

WTB: Black Leather Acura GSR seats

kfr01

Gold - Posts: 2,121

This member has made a donation to the12volt.com. Click here for more info.

Joined: April 30, 2003

Posted: April 01, 2005 at 2:54 AM / IP Logged

A coax digital connection will still carry current. Ground loops are still possible. Noise can enter the system this way. An optical digital connection would not have this problem. However, neither are always perfect because of jitter issues.

At some point a DA conversion must be made. Unless this conversion is done in the amplifier itself, there will be interconnects carrying an analog signal.

But yes, other people have thought of this too. Check out this Optical Digital Reference line by Pioneer UK: http://www.pioneer.co.uk/files/brochures/04_CE_ODR/04_CE_ODR_EN.pdf

McIntosh Labs also sells an outboard car audio DAC.

To me this sort of upgrade should be far down the list of priorities if you're operating on a budget. It should be a choice made to improve sound quality - not as the most expensive noise band-aid known to man. :-)

If you convince yourself you need something like this I'd first suggest making your front stage near perfect so you'll actually be able to appreciate the sonic upgrade.

New Project: 2003 Pathfinder

DYohn

Moderator - Posts: 10,741

This member has been recognized as an authority in Electrical Theory. Click here for more info.

This member has been recognized as an authority in Mobile Audio and Video. Click here for more info.

Joined: April 22, 2003

Location: Arizona, United States

Posted: April 01, 2005 at 9:16 AM / IP Logged

The answer to your question is yes and no. Yes, it is possible for a DSP to remove specific types of noise from the signal path. It can just as easily introduce other types of noise (like digital artifacts.) And No, audio that you can hear has to be analog (speakers and the amplifier that drives them.) The power from your vehicle's alternator (or your home power system) is analog and seperate from the signal path. So any noise being introduced after the DSP (in the amp or the speakers) or that is not affected by the DSP (in the power chain) cannot be controled by this sort of digital signal manipulation.

Digital is a great way to easily manipulate and transport audio files, and it can achieve excellent sound quality more cheaply than can analog equipment. But it is not a cure for all ills.

Support the12volt.com

SiDogg

Copper - Posts: 65

Joined: July 02, 2002

Posted: April 01, 2005 at 10:33 AM / IP Logged

Right, I understand that any noise interference in my amp or the piece doing the DA conversion (the DSP itself) is still susceptible to noise. But most car audio devices are built in a way to avoid noise.

The source here, if you are wondering, is a computer playing DVD and MP3 files.

It is probably a great home to noise; however, I can avoid all noise if I unplug the LCD (VGA port). So the LCD is allowing noise to go through it, into the VGA port on the motherboard, and thus resonating out into the RCA cables to the amp. I figure inserting optical and digital DSP between the motherboard and amp, I will no longer have this noise issue, since it cannot resonate into the amp any longer. And the PC should not have noisy digital music, because it wouldn't be doing any ADC conversion since the DVD (IDE) and MP3 (binary data) are all digitally accessed.

Or am I on crack? :)

DYohn

Moderator - Posts: 10,741

Joined: April 22, 2003

Location: Arizona, United States

Posted: April 01, 2005 at 10:44 AM / IP Logged

OK, so now we move from theory to application. You're telling me you have a computer music source and a noise problem. Is this in your car or in your home? What kind of noise are you hearing?

The two most likely culprits are your sound card and the system ground plane. What sound card are you using? How is the system grounded?

And by the way, a DSP (digital signal processor) is not the device that provides the digital to analog conversion. That is the DAC (digital-analog converter) and in a computer is your sound card.

Support the12volt.com

Drewt

Copper - Posts: 183

Joined: January 04, 2005

Location: United States

Posted: April 01, 2005 at 11:50 AM / IP Logged

what you can do is get a card that will give you an optical output from your computer, then take that to a flying cow DAC in the back, and have your amp pretty close to that. The noise verry well may be comming from the other stuff in the computer, interacting with the sound card.

-Drew

Edit: for the very best sound quality, you'd want analog throught, no digital whatsoever. But, since the audio industry has made us think that CD quality is "perfect", no one else knows that....

It would be slick if you could get an amp like the Alpine MRD-M501, and pull out the ADC in that, and push the digital signal straight to the DSP...

-Drew

SiDogg

Copper - Posts: 65

Joined: July 02, 2002

Posted: April 01, 2005 at 7:28 PM / IP Logged

DYohn: It is not my PC. You are not listening to me. If I unplug the LCD VGA cable to the PC, the noise is gone. Maybe because my PC is not grounded, I am letting the noise go through to the RCA cables, but it is not my PC making the noise. The noise is about 200Hz and it is a buzz like "line noise". It is not "white noise" though. The amp can filter it out, but it's too high for me to keep the filter on as it kills my mids.

By the way, I did try another sound card -- one certified with THX and is 7.1 capable and has an HD codec of some sort as well. It is the Audigy 2ZS from Creative. But it installs by screwing into the PC case, because it's a PCI card, and it made the sound even worse, by making the noise come from the PC case as well as from the LCD VGA cable. I tried grounding the case all over and even extra grounds for the motherboard. No luck.

Only ground thing I haven't changed yet is the ground distro block in my trunk... *sigh* Maybe I will just to see if that helps.

Drew: That is what I'm planning on doing. My motherboard has native S/PDIF out. :)

DYohn

Moderator - Posts: 10,741

Joined: April 22, 2003

Location: Arizona, United States

Posted: April 01, 2005 at 8:12 PM / IP Logged

What you are describing are textbook symptoms of a ground loop probably caused by trying to integrate a PC into an automobile. What are you using for a power supply?

Support the12volt.com

customsuburb

Gold - Posts: 1,813

Joined: January 17, 2004

Location: United States

Posted: April 01, 2005 at 8:16 PM / IP Logged

Drewt wrote:

...It would be slick if you could get an amp like the Alpine MRD-M501, and pull out the ADC in that, and push the digital signal straight to the DSP...

-Drew

Whoa, this Alpine amp has two optical inputs and what looks like a built in dobly digital and DTS processor... https://iweb.alpine-usa.com/pls/admn/item_info?p_item_name=MRA-D550&p_category=40&p_subcategory=130&p_main=10 That would be cool if you ran the optical output from your soundcard to the input on that.

Next Page >

Printable version

You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot delete your posts in this forum
You cannot edit your posts in this forum
You cannot create polls in this forum
You cannot vote in polls in this forum

Search the12volt.com

Follow the12volt.com

Disclaimer: *All information on this site ( the12volt.com ) is provided "as is" without any warranty of any kind, either expressed or implied, including but not limited to fitness for a particular use. Any user assumes the entire risk as to the accuracy and use of this information. Please verify all wire colors and diagrams before applying any information.