Looking to introduce optical to permanently hide ground noise

S4Per · 01-22-2007, 08:00 PM

Hi All,
I know there are hundreds of threads and pointers around troubleshooting and isolating ground noise and that the subject line here truly does only implement a band aid, not a fix. I've spent more than my share trying to get rid of the noise, and I'm just ready to punt on it. That said, I'd love some advice on what I would need to do/get to go down this path.

Right now I have an Aopen i945GTt-VFA motherboard with on-board (Azalia 7.1) audio. I could care less about 5.1/7.1, I just want good ol'e 2 channel stereo ;-) This mobo does have an S/PDIF connector on it (relevant for my quest?)

I have 2 Zapco DC reference amps (no optical input). I'd like to go from PC directly to them...while having optical somewhere in the middle to leave the noise behind.

What would my options be? Would this actually get me my desired result? Would I need an external sound card AND something else to do this? Would signal quality erode significantly if there are multiple devices?

I'm a little clueless in this specific area, so any and all help is appreciated.

Thanks,
Per

scott_fx · 01-22-2007, 08:06 PM

zapco has a dac with digital inputs. check that out. if not there are other dacs available (check the dac sticky or post questions back in here). just make sure that the noise is coming from the pc. i'd first hook up a portable device to the amps directly and start the car, see if the noise is gone or if it's still there.

durwood · 01-23-2007, 01:34 PM

Other ways to hide ground noise:

-External Sound card run all the way to the trunk. The USB signal does not carry audio but just digital data. All audio is processed outboard. USB will not pick up induced noise on the audio, but there is a risk of induced noise on the audio cable out of the soundcard. Proper wire mangement will avoid this.

-Balanced Analog signal rejects noise/ground loops and produces a cleaner signal

-Optical/Coax digital out to D/A convertor. Search for D/A convertors if you want this.

psyrex · 01-23-2007, 01:51 PM

I use an Extigy in my trunk with only a very short cable to run between it and my amps. I use the USB for the digital data (and the noise removal feature it inherently exhibits) all the way to the trunk like how Durwood recommended. However, there is still noise from the Extigy itself, and I eventually had to throw in the towel and actually buy a line driver (Audiocontrol Matrix rocks!) and everything is crystal clear now.

durwood · 01-23-2007, 01:57 PM

Quote: Originally Posted by psyrex

I use an Extigy in my trunk with only a very short cable to run between it and my amps. I use the USB for the digital data (and the noise removal feature it inherently exhibits) all the way to the trunk like how Durwood recommended. However, there is still noise from the Extigy itself, and I eventually had to throw in the towel and actually buy a line driver (Audiocontrol Matrix rocks!) and everything is crystal clear now.

Line drivers work in some cases, the Audiocontrol piece has different grounding options inside for the audio path to eliminate ground loops. The matrix is a nice piece.

What kind of noise did your extigy have? Did it change with engine speed or was it just constant noise? I'm curious.

psyrex · 01-23-2007, 02:44 PM

My Extigy was powered by a DC-DC converter, so it was mostly isolated from engine noise. Because of this, I found that the Matrix works best is fully isolated ground mode.

As for noise, oddly enough the "line in" picked up on harddrive access noise even though the Extigy was 6' away. Making sure all non-essential channels were muted is important in removing noise. At full volume (Main, Wave, and winamp) with a 1KHz source, the Extigy barely lights the 1V LED on the Matrix, so you can imagine how close the signal is to the noise floor. I found the line driver to be a godsend and recommend it even when using digital to avoid noise.

durwood · 01-24-2007, 08:43 AM

Quote: Originally Posted by psyrex

My Extigy was powered by a DC-DC converter, so it was mostly isolated from engine noise. Because of this, I found that the Matrix works best is fully isolated ground mode.

As for noise, oddly enough the "line in" picked up on harddrive access noise even though the Extigy was 6' away. Making sure all non-essential channels were muted is important in removing noise. At full volume (Main, Wave, and winamp) with a 1KHz source, the Extigy barely lights the 1V LED on the Matrix, so you can imagine how close the signal is to the noise floor. I found the line driver to be a godsend and recommend it even when using digital to avoid noise.

AH I C. Yes that is true. It's a good idea to keep things muted that you arent using.

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