Its always this - a grounding issue.
I've finally finished my Car PC, installed it, and the sound is dreadful.
The M10000 board is producing a lot of background noise, even when I run it in the house powered from a laptop PSU, there is a constant buzzing that you can hear at about -24db (on my home amp)
It's also picking up noise from the car itself. I don't have any ground loops going on (I even tried disconnecting the shielding from the cable), grounding the PC directly to the battery, or both PC and amp directly to the battery makes no difference.
If I plug headphones into the PC, I can't hear any of the noise, though that may be due to the lack of amplification. If I plug my laptop into the amp instead of the Car PC, there is no noise.
I honestly have no idea what to do now. I've read the FAQs about alternator whine, but none of the suggestions seem to work. The only solution I can think of is to buy an amp with a digital input, but I don't have the cash for that.
Its always this - a grounding issue.
that too - but I can't help but wonder how you have it all connected?
have you boosted the voltage level from the computer to the amp? are you running from the mobo direct into the amps or are you running from a sound card? what?
I'm using the onboard audio to do this. I wouldn't know how to boost the voltage level to the amp so I don't think I've done this, just made up a standard jack to two RCA lead (both with and without the shield connected at one end)
My power wire is from the battery and splits two ways near the PC end to drive the PC and the amp, the earth wire is split in a similar way and is attached to a grounding screw just in front of the gear lever. There is something else grounded there, that is part of the car, so I figure it's a good ground, but I have also tried connecting it to the battery. (using a jump lead, but hey, it works!) and have also tried disconnecting the PCs ground and then directly attaching that to the battery, leaving the amp connected to the original ground.
The problem may have something to do with there being a voltage difference if you put the prongs of a multimeter on the casing of the PC and the amp, despite them having the same ground and power sources. I have no idea how to fix this, or why it's happening.
well that's your problem - the onboard audio signal is WEAK...
like .5v, that's extremely weak
you say that you've made the connector? are you SURE the connections are good? good solder joints/techniques used, etc....
The connector is fine, but I have also tested with a jack -> 2xRCA socket and then a standard RCA lead with no difference.
So, what can I do about the onboard audio signal to improve it since surely it's going to pick up the same problems if I hook it up to some kind of pre-amp? will a ground loop isolator help at all?
Also, I don't think that is all of the problem, as well as a background noise which is explained by what you just said, I'm also getting terrible alternator whine.
the preamp will help it honnestly - it will help to boost the line voltage
a ground loop isolator won't hurt!
Ya I had a similar problem with mine. I had a SoundBlaster PCI Sound Card that has alot of noise in only a 3ft shielded rca run. So I borrowed my buddies line driver (preamp) to see if it helps. His line driver displays the input voltage and it was only .7 volts so after the line driver it boosts it to nearly 8v. Which got rid of the noise completley. He suggested to make the run of the cable at the low voltage as short as possible so i made it like 10 inches and now its great. Im using his untill my new pld-1 comes in the mail. Gl hope this helps.
Well, this is where things get confusing as far as my amp is concerned.
It's only a little one, actually sold as a line driver, but they claim it will do about 20W RMS, which is enough to drive the stock front speakers in my car.
I think I can solve the general background noise just by turning this amp down a bit and actually using it as a line driver, but surely adding an amplifier afterwards will just bring the noise back again since it's coming from the motherboard, not from the cable.
And then we have the alternator whine to get rid of too
turning the gains down will help the situation, any time gains are turned up a great deal it can cause some of the same problems that you're experiencing