Nasty, Nasty PC Audio

akwash79 · 05-08-2007, 05:42 AM

Where to begin?

I have a M10000 powered by the m1-atx psu. Both amp and pc are wired directly to the battery using 10awg wire and both grounded to the same spot under a bolt in the trunk(I DID sand this down to bare metal). The audio is going out directly to the 4-channel amplifier(no HU).

1st attempt - I used the onboard sound and got alternator whine and buzzing sound whenever the HD was being accessed or duriing mouse movements(on touchsscreen). When removing the RCA wires from the amp, the noise stopped.

2nd attempt - I used the Turtle Beach Roadie USB sound card for audio out. While this improved the sound quality greatly, the same alternator whine still persists. But...... get this......I no longer hear a buzz when the hd is being accessed or during mouse movements, the buzz is now constant and ONLY goes away when the hd is being accessed or the mouse is moved. WEIRD. I hooked up a pair of headphones to the audio out from the roadie and I did not hear any noticeable noise.

Also, my rca cables are no where near the power or ground wires.

My next steps:

1. Try hooking a cd player or ipod directly to the amps to see if the noise is still there(may be difficult to come across one of these without purchasing) I may try using my pocket pc, just need an adapter.

2. Ground loop isolaters - although this really doesn't SOLVE the problem just masks it.

3. Ground amp and pc under 2 different bolts?

4. Better RCA cables(although I really doubt that this is the problem)

Any other suggestions before I lose my mind?
99 Mercury Cougar

akwash79 · 05-08-2007, 05:47 AM

Oh, I also tried muting everything even the 'Master' volume to no avail.

DarquePervert · 05-08-2007, 07:06 AM

Run the power wires as far away from the audio signal wires as possible. POwer up 0one side f the car, audio up the other side.

durwood · 05-08-2007, 07:30 AM

akwash79 · 05-08-2007, 08:22 AM

no power wires near any audio wires except at amp connection of course

RedGTiVR6 · 05-08-2007, 08:45 AM

what RCA cables are you using?

the walmart RCA cables or the like or actual quality RCA cables that you spent a little bit of money on?

durwood · 05-08-2007, 09:44 AM

Quote:

I hooked up a pair of headphones to the audio out from the roadie and I did not hear any noticeable noise.

Might indicate a ground loop between your equipment. Other thing to watch out, keep your video cable away from your audio cables.

Might possibly be bad soundcard or chipset drivers but I don't think that is the case.

Vodkapete · 05-08-2007, 06:27 PM

Quote: Originally Posted by durwood

Other thing to watch out, keep your video cable away from your audio cables.

I've not heard this before - how come?

Ian

RedGTiVR6 · 05-08-2007, 06:36 PM

same reason as power and signal and RCA and power, etc.

symon_say · 05-08-2007, 08:24 PM

It really doesnt matter if you put your power cable and your RCA together, the loop that the power cable creates is nothing to care about is you install your equipment propertly. Is more important to have good quality RCA than this.

I have a little audio store, and install a lot of systems with the cables in the same rail, and it doesnt create a loop, and have solved a lot of cases that they have noise and the problem were some bad conections, or bad ground in most of the cases, or maybe some equipment interfering each other, so try the options you post those solve the problem in most case or try to put as far as you cant you carpc and your amp.

akwash79 · 05-08-2007, 10:27 PM

Quote: Originally Posted by symon_say

so try the options you post those solve the problem in most case or try to put as far as you cant you carpc and your amp.

Many people here advise to ground the pc and the amp at the same spot. By doing this, is there a possibility of them trying to ground through each other? Just a thought.

As far as my RCAs, they are better than wal-mart quality but not quite Monster cables. Also there are 2 different brands going to front and rear and they both produce the noise.

DarquePervert · 05-09-2007, 08:15 AM

Quote: Originally Posted by symon_say

It really doesnt matter if you put your power cable and your RCA together, the loop that the power cable creates is nothing to care about is you install your equipment propertly. Is more important to have good quality RCA than this.

I don't believe that anyone said having signal cables running alongside power cables created a ground loop.
The power cables put out electro-magnetic interference that can affect the signal, causing noise in the audio and distorted images on the video. EMI is something that is ut out by every electrical cable whether it's long or short, AC or DC, a few milliamps or hundreds of amps. It's still there to some degree.

I'm don't going to argue your experience or skills, but the general consensus is that power cables and signal cables should be seperated. That' not just by this crowd, but also by the high-end car audio crowd.

Quote: Originally Posted by akwash79

Many people here advise to ground the pc and the amp at the same spot. By doing this, is there a possibility of them trying to ground through each other? Just a thought.

No. Electricity flows in a circle. In throught he power and out through the ground, basically. It's kinda like a NASCAR race: It only goes one way unless there's a problem.

davidingermany · 05-09-2007, 09:25 AM

Try turning your gains down on you amps. Another option is a line driver as close to the PC as possable. The line driver will provide a cleaner output with a higher voltage and reject any signal noise you may be having.
David

ccjustin · 05-10-2007, 12:35 AM

is the outside part of the usb cable the ground? if so i would add a ground from it to the main ground for the amp. i have a tendency to believe the pc has a lot of resistance between where the power and ground come in and the signal goes out.

greatwhite · 05-10-2007, 06:42 AM

I've had everything form alt whine to pc noise to static from nowhere.

All I can tell you is to move things around, and try grounding things in different orders/places.

I eventually cured my issues with carfeul cable routing (audio and power), by putting my comp in an all metal case and grounding it to the vehicle (well, it's bolted to the body structure). My amps are mounted on mdf and go to a common ground with equal length cable runs.

I am even running an inverter right now and have no noise! (too poor right now for a DC-DC solution

) Once again, careful positioning, routing and grounding makes it viable.

It just seems you have to experiment to find the right combo for your setup and vehicle.

Good luck

User Name		Remember Me?
Password