Thread: got sound?

Originally Posted by DodgeCummins

I wouldn't have expected your Epia to have problems under normal circumstances either.

d00d =) that doesnt answer my question. Because some car audio shops have convinced me that if I plug in a CD player into the receiver and I charge the CD player at the same time from the car battery, the CD player will burn. To be honest I never thought this was possible before this.. but now I think they are probably right.

Let me put it this way. My Pioneer stereo and a number of folks on this site's stereos are used in this way. Some through inverters some like mine through DC-DC.

If yours burns up equipment, then your stereo is the problem.

If you don't have enough faith in the quality and safety of your Head Unit, then toss it and get a real one.


Also you still haven't stated what brand unit, or what kind of car, or if it is positive or negative ground system etc.

A cell phone might explode if I use it at the gas station...but not likely.

You might try to find someone with some electronics knowledge...and not the monkeys at the car stereo shop...I don't even waste my time talking to them.

You need to talk to someone that can take some measurements on your stereo gear, your hookups etc.

The fact you are blowing fuses raises two red flags...one-that something is very wrong, and shorting out, two-that you have limited knowledge about the cause.

The only thing that I can guarantee, is that if this happened to me I would,
a) take my digital voltmeter and start testing.
b)check out the schematics of the HU and everything else,
c) check the voltage potential between the mobo and vehicle ground,
d) check the voltage potential between that aux in jack and vehicle ground,
e) check the voltage potential between the aux jack and the mobo.
f) do loaded voltage measurements of the mobo power supply.
g) do some continuity tests
h) take some cheap portable tape player or something, and test the aux-in.
i) ensure the engine block is well grounded to the frame/chassis
j) ensure the battery is well grounded to the frame/chassis
k) ensure the stereo is well grounded to the frame/chassis

My only guess on the subject, is that the stereo has a bad ground, or short, and is using whatever is plugged into the aux jack as the ground, if the one ground is not connected to the other ground, then your soundcard ends up being used for the ground...it can't take the load, and burns out.

Surely there is someone where you live, with real electronics knowledge...

Alrighty, thanks. That clears up one thing. So those folks and the audio shop didnt know what they were talking about.

I asked them that when I suspected something was wrong with the setup, and asked them to check the wiring. They simply said.. no they wont check the wiring. I asked why and then they went to great lengths to explain that if I connect something to the battery in the car and put it in the stereo jack on the receiver then it will short. They havent seen my car or the stuff I have in it yet at the time. *shrug* they seemed confident.

I did take an ohmmeter and connect one end of it to the battery -ve and the other end I just plugged into the aux-in and I had an ohm of 0. I thought it was shorting because the +ve signal from the stereo plug was touching that ground in the receiver.

When I asked the car stereo guys about it, they told me that all car stereo setups are this way. Heh.

THat's why I was looking into building a circuit with a capacitor to separate the DC voltage coming in directly from the battery to the aux-in but I found a ground loop isolator and I figured this has transformers inside and would do the job.. which it did.

By the way, as I said before.. my receiver is one of those el cheapo ones. I dont even remember what brand it is.. something with funky names. I only bought it after testing it because it didnt have those noise coming in when you're connecting a walkman into the aux-in input.

If you had an ohmeter measuring resistance, then it makes sense that there would be no resistance from batt- to the aux in jack...at least the outer part. (the common...the base...the - )

If you were to use a voltmeter, then hopefully you would read zero volts with that same hook up...that means that vehicle ground is the same as chassis ground on your radio...that is a good thing.

Next i would do the same test on the computer thing.

I guess what the monkeys said was partially true. If you were to hook a wire from the battery + and touch the receiver aux in...that would be a short...duh...you knew that much I am sure.

There is more electrial theory I could get into...but that won't help.

The reason I keep saying that you should be able to plug it in and go (If everything is wired correctly) is that the aux out of your computer only puts out a few volts and maybe half an amp...that in not even enough juice to visibly see a spark, let alone burn out any parts.

The aux in on the stereo is set up the same way. low voltage and low amps...there is nothing there with enough power to do any damage.

However is something is miswired, then you could have more volts available and/or more amps available...that would zap anything you plug into it.

Stick that stereo plug into the radio (while turned on) and measure voltages from ground to all three parts of the plug...

If we knew the brand, then maybe we could look up the specs on the internet...

Since it has been 4 days since this topic started, surely you have looked at the unit...or is it so generic that it doesn't even have a name...like metrosound, or sounddesign,

Originally Posted by masch

Hola people.. Been a while since I was last here.

I just got my epia 800 mobo back after 6 months. I sent it for repairs when I found out that no sound was coming out, I think I must've fried the built in sound card.



I setup my carPC thru an inverter and a small 140W psu. I tested everything on my table desktop and it was all working fine. Then I put the setup into my car, and it boots fine. Just when I connect a stereo cable from the built-in sound card of the EPIA to the aux-in of the car radio, I hear the epia shut off.

To my dismay, I realized that the sound card was burnt again.

I put a lower fuse in the inverter and bought a cheap sound card to plug it into the PCI slot. However this pci sound cards have a higher tolerance than the built-in sound card on the epia. When I connect again the stereo cable from the audio-out of my sound card to the radio, it shuts off.. but this time only the fuse gets burnt.

I went to get a ground loop isolator.. it looks like a closed cylinder but I think it has transformers inside. I made a couple of stereo-to-RCA male and female connectors because the input/output of the isolator are RCA type connectors. So when I connect the setup to the radio using the ground loop isolator, the fuse no longer blows and I can listen to the sound fine. I think this works because no longer is the current flowing from the battery->inverter->PSU->epia->sound card->radio->battery because the transformers have no DC connection, I mean electrically the transformers dont touch each other. The stereo cable must've completed a loop back to the battery that is of the lowest resistance, hence burning the fuses due to the high current.

So you n00bies out there.. watch out before you plug in your sound card directly to the radio if you're using EPIA! I learned the hard way and I think I may have to go repair the mobo again.

Now I have a different problem..

1/ I can hear some static noise coming out of the radio and the radio screen is picking up some sound that I can see due to the animations.. it seems like some high frequency noises. I dont know how to fix this. I already have a ground loop isolator. Could it be because I made the stereo-RCA cable myself and I did a poor job at it? If I were to buy a ready-made stereo-RCA connector, should I replace the one connecting the sound card to the ground loop isolator or the one connecting the ground loop isolator to the radio?

2/ To hear songs on the speakers, I cant plug in the stereo plug perfectly inside, because then I'd hear sound coming from only 1 speaker where as the other is distorted. To hear the sound perfectly, I have to slightly pull the stereo connector out so that it doesnt completely go in but still connects into the aux-in of the radio. This sucks because when I hit a bump in the road, the connector comes lose and I lose audio and I have to carefully place the connector back in slightly again.

The stereo connector looks somewhat like this:
(incoming cable)===|==|=- (stereo tip)

I have the two grounds from the RCA (outer ring) connecting to the stereo tip and the one from the white RCA core to the middle and the one from the red RCA core to the other end of the stereo plug. I say white and red RCA core to mean the connector is white and the other is red.. there are two incomings to the RCA connector.. one to the outer ring which I assume is ground and in the middle there is a male center that looks like a shaft which I assume to be the core..

I have no idea what to call these components so I hope you guys understand what I mean. I'm new at these sound things so I hope you can shine some light on what I'm doing. I just connected stuff which I thought to make sense.

Thanks in advance.

Can I ask a question, why are you even mucking about with this Headunit? if it is blowing your soundcard when you connect it to the Aux in then it is *****ed.

Remove your headunit, find a bin, throw it in, then go buy a Kenwwod/alpine/Sony/JVC etc etc

Dont muck about with cheap *****.If you cant afford a new HU then go buy a cheap amp and plug it in there.

I cant belive you are trying to test the wiring on this HU.

Even if you fix the problem with power going to your Aux in who knows what elese might happen.

True...

That's some great advice sunglassesron. =P Too bad if I put it in the bin, and get a preamp, I wont have radio at all.

Dodgecummins, I checked all around the outside and it doesnt have a brand name. Perhaps if I take it out I could check at the back but I havent done that yet. If I had a digicam I'd take pictures to show you.

So basically thanks to you guys I've established 1 thing:
It is OKAY to plug in a player that's charging from the same car battery as connected to your headunit and connect that player to the headunit via the AUX-in input.

That means the guy at the car accessory shop didnt even know what he was talking about.

So back to the original question, as I have already resolved that soundcard blowing up problem by putting a ground loop isolator in between, however I notice this distortion or noise when I pump the volume up. I thought GLI's are supposed to filter those out.. or could it be because of the (supposedly) messed up wiring on the headunit?

Alright, your wiring is screwed up someplace. We all know that. The only way that the scenario you are describing could happen is if there is power being transmitted where no power should go, ie through your rca/miniplug cable. So do one of the following.

1. To see if the computer is the problem, try using a a CD player with your radio

2. To see if your wiring is the problem, try either wiring it correctly or buying a proper wire (available at Circuit City, etc, and probably cheaper then the wide variety of fuses you've purchased.)

3. To see if your head unit is the problem, hook your carputer up like normal but listen to the mobo with headphones or hook some pc speakers or something up.

This will isolate what component is the problem. My guess would be either your wiring is improperly insulated and touches a hot wire someplace, or your head unit has serious and unsolvable issues. If you can't diagnose the problems with your head unit yourself, there's no way we can help you fix them over the internet.

Originally Posted by masch

That's some great advice sunglassesron. =P Too bad if I put it in the bin, and get a preamp, I wont have radio at all.

It is some great advice. If your computer works fine when you listen with headphones, or if your CD player goes BZZZT, get that thing the heck out of your car. I'd stomp on it a few times, personally. Screw radio...I've been without radio for 6 months just because i was too lazy to extend the antenna wire when i relocated my head unit...if you are choosing radio over a working carputer then you're on the wrong forum. Also, if you get your carputer running, you can always add computer controlled radio later.