The Most Incredibly Un-killable Ground Noise ever...

**Nola111** · 10-06-2008, 02:45 PM

Hey guys,

Now that I've determined that the 5v box will turn on my amp, but my system doesn't get loud enough w/o another amp in front of it... would there be any benefit in going back and getting that line driver and seeing if that makes a difference in sound level when used in conjunction with the 5v box? I'm guessing probably not, right? A line driver doesn't actually give any volume boost, correct?

**insaneramman** · 10-06-2008, 06:57 PM

Nola I'm just (as you are) walking in the dark. I hope WoofnStuff can help. I am lost. I will read and learn from here on out. Wishing you all the luck I can.

**Woofnstuff** · 10-07-2008, 03:51 PM

just looking at my install images it dosnt show as much as i would like...

I cheated, but it works
you can see the green heatshrink next to the red power wire, thats the wire that goes to the pc and the screen, i wired them into the amp power input both the positive and negative,
the HU is wired off the car loom i think,

i did get a noise issue at the HU end where the rca plugs were running close to the vga cable, with the application of a few cable ties to hold them apart its all good

with your system it might be easier and cheaper to put a new amp in.
im slightly sure that the vw system uses balanced audio, below is a brief on balanced audio... ill look for a more basic one...

Is there a simple explanation of the difference between single-ended and balanced operation?

In this context, the terms "single-ended" and "balanced" describe the type of electrical interface between components: i.e. preamplifiers and power amplifiers. Single-ended interfaces use a "common" conductor (shield, ground or instrument chassis) as a signal return path. Balanced lines, on the other hand, use two dedicated conductors to provide forward and return paths for signal. The ground connection in balanced configurations is accomplished by means of a third, dedicated, ground conductor. Any two components in your system will, most likely, have a measurable voltage difference between their chassis. When a single-ended cable is connected between these two components, this voltage difference will appear along the common conductor (shield) of the interconnect. As a result, the shield will now carry the parasitic ground noise current between the two chassis. Since the shield is directly in the signal path, the voltage drop along the ground conductor will be combined with the signal that the interconnect carries. The result will be added noise and distortion introduced directly into the signal path. In a balanced system, a separate shield or ground conductor will be used to connect the two chassis together, reducing the voltage difference between them. But the voltage drop across the shield will not add to the signal, because this third conductor does not carry the signal. What flows through the balanced interconnect is a clean signal, separated from extraneous ground current and noise. Additional benefits are derived from the fact that balanced circuits are inherently symmetrical. The balanced nature of the internal circuit greatly reduces transient demand on the component power supply, further improving signal integrity and noise immunity.

**Nola111** · 10-07-2008, 05:43 PM

Thanks for the post Woof.

It would be very difficult to replace the VW amp b/c of it's proprietary connections and wiring, and also because the speakers and amp are meant to go together. In the absolute worst-case scenario I would consider it, but that would mean also replacing my speakers. But since I have had a car pc in this car with this amp that did NOT have any noise problems, I know there has to be a way to kill the noise. I would go back to my old setup if the sound quality wasn't so far below what I have now and it didn't lack power on the PC side of things.

Thanks for the paragraph on the balanced inputs. As a singer/musician I've had to deal with balanced vs. unbalanced in live performance and recording situations (mics are almost always balanced, guitars unbalanced).

I still have yet to figure out how my pc stays powered on with no ground connected. I disconnected the ground wires and unplugged everything else hooked up to the pc, and it still stayed powered on. The only thing I can think of is that the PSU itself is still somehow grounded even when the ground wires are disconnected. I'll keep checking.

I am going to try what you have done b/c at this point I am willing to try anything. I'll let you know how it goes. Thanks again.

**visenri** · 10-07-2008, 05:56 PM

Originally Posted by Nola111

I tried all you guys' suggestions too.

Did you try the short circuit tests (Input of TIO) i suggested, which were the results from the test?. Was the noise still there, if yes, you could try to power the TIOs from the same ATX power supply cable, but don't connect this cable to other devices, only the TIOs, and run the short circuit test again.

If noise still persists, you can put TIOS far away from computer (30cm), with some power supply extension cables and run the test one more time.

If noise still persist, you can put TIOS powered directly from the same power point of the amplifier, just to run one more time the short circuit test.

Tell me the results, i am allmost sure that the TIO is the device that is introducing the noise.

You can get a very cheap and easy to buid voltage doubler, you can wire two GLI with outputs in series (L in series with L and R in series with R), and inputs in paralel to double the audio level of your sound card, if you have two ground loop isolators, try it, this, combined with the 6V box wiring will make unnecessary the use of the TIO.

To make this GLI doubler, you must check that output grounds of RCA are not internally short circuited, check it with a multimeter, if measurement between the two output grounds is 0ohm, you can't build the doubler wit that GLI.

Tell me if you need a little schematic.

**Woofnstuff** · 10-07-2008, 07:01 PM

Originally Posted by Nola111

But since I have had a car pc in this car with this amp that did NOT have any noise problems, I know there has to be a way to kill the noise. I would go back to my old setup if the sound quality wasn't so far below what I have now and it didn't lack power on the PC side of things.

i must have missed that...
what is the motherboard / sound card (just found in first post) you have now and what did you have? did you use the same soundcard in the last setup?

and you will notice .. guessing here.. on the psu its connected via screws to the case, and the screw holes have and earth point on them. is your case touching anything metal? or bolted to the car? (just re reading early posts)

what things do you have plugged into the pc?

**Nola111** · 10-07-2008, 08:55 PM