Help needed with subwoofer/amp/carpc install

Toxic0n · 07-17-2009, 01:44 AM

Hi,
I've got a CarPC running perfectly on this motherboard
http://www.avalue.com.tw/products/ECM-3611.cfm

It's got onboard AC97 audio. I have a 3.5mm wire running to the headunint - everything sounds great.
I am trying to add a subwoofer to the system. I've got a 10" Pioneer single coil sub - 4Ohm, 700W max, 350W RMS
I have an Xtant A2002 amplifier.

http://www.xtant.com/archives/html/t...02_4004Man.pdf

I used a 3.5mm Y-splitter + 3.5mm to RCA converter to direct the sound to both my headunit and the amp. I then hooked up the amp to the sub in bridged mode but I am not getting any sound. The amp is set to Low Pass, Balanced Input Off. Any ideas?

jake789 · 07-17-2009, 01:50 AM

You should wire the pc to the aux in of the deck, then use the sub output of the deck to the amp.

Toxic0n · 07-17-2009, 02:00 AM

the deck does not have a sub out. Is there any other way around? I thought this was supposed to work this way without any issues...

Toxic0n · 07-17-2009, 02:14 AM

One more thing, when I unplug the amp/sub from the Y splitter, it seems the sound coming from my speakers actually gets louder. No idea why.

almera · 07-17-2009, 02:28 AM

How about wiring the pc to the aux in of the deck, then use the speaker output of the deck to the amp.

From your amplifier owners manual;

Optional Performance Upgrades
High Level Adapter (HLA)
This adapter allows you to connect a source unit with speaker level outputs to your Xtant amplifier.

Toxic0n · 07-17-2009, 02:46 AM

That might be a bit difficult to find. So basically there is no way to go from speaker out on my sound card to an amp? I've seen others to it on this site without any problems

pancit175 · 07-17-2009, 06:02 AM

The most important part of your diagram that I'm not seeing is if you connected the remote out from the deck to the amp. And is the amp turning on? Have you checked your +12v and GND connections to see if its getting the correct power as well? Is the Fuse in?

Quote: Originally Posted by almera

How about wiring the pc to the aux in of the deck, then use the speaker output of the deck to the amp.

From your amplifier owners manual;

Optional Performance Upgrades
High Level Adapter (HLA)
This adapter allows you to connect a source unit with speaker level outputs to your Xtant amplifier.

This is otherwise known as a Line Out Converter (LOC) and can be found nearly everywhere that sells mobile audio electronics

Quote: Originally Posted by Toxic0n

That might be a bit difficult to find. So basically there is no way to go from speaker out on my sound card to an amp? I've seen others to it on this site without any problems

There would be no other way I would recommend doing this considering your current setup. Otherwise you would get uneven signals going to the amp anytime you increase the volume from the PC or the Headunit.

bratnetwork · 07-17-2009, 08:52 AM

Hook an ipod directly to the amps rca inputs through the head phones port and turn the amp on and play music. turnthe volume up and down on the ipod. if still no sound out of the sub then its and amp/sub issue not the wiring or pc. Also check the gain setting on the amp. Most amps I've worked with have either a gain adjustment or level in adjustment that will affect the over all volume of the output of the amp.

Toxic0n · 07-17-2009, 09:19 AM

The amp is turning on - the red LED on it is on. I have the remote wire connected to the remote on lead on the M1-ATX power supply. I hooked up my iPhone and played music on it and could not hear anything from the sub. I tried turning up the gain and the bass boost. Looks like a amp/sub wiring issue? I just don't see what could be wrong. Do I have it bridged correctly?
Here's some pics of how it's wired up:

http://img20.imageshack.us/img20/4998/dsc05674k.jpg
http://img268.imageshack.us/img268/2492/dsc05675d.jpg
http://img268.imageshack.us/img268/4880/dsc05677r.jpg

Regarding the uneven volume issue, if I get this working, can I hook it up to the line out on my sound card? The volume for that is controlled independently from the master volume, is it not?

soundman98 · 07-17-2009, 09:44 AM

the best way to connect it would be to use the head unit speaker outputs. using just rca cable from the pc would work, only if you were amplifying all of your speakers.

by setting it up the way you have, you will now have 2 volume adjustments--the one on the radio--for the main speakers, and on the computer, the one for the main speakers, and sub. if you ever decide to listen to the radio, or a cd/tape in the radio, the sub will not work.

being that you did not get any sound w/ the ipod, i will have to say that you are going to need to test the speaker leads from where they are connected at the amp, unplug them, and test them w/ a ohm meter to double check that you have the proper ohm reading for the sub, if that is good, then it could be a bad ground, or a defective amp.

blazini · 07-17-2009, 11:45 AM

Quote: Originally Posted by Toxic0n

That might be a bit difficult to find. So basically there is no way to go from speaker out on my sound card to an amp? I've seen others to it on this site without any problems

That's because most of them (like me) aren't using a headunit. In my case I go directly from the soundcard to my 4 channel amp which has RCA line-outputs, to my subwoofer amp.

You have to remember that a soundcard is meant for home-audio type line-in/line-outs. Car audio equipment has higher voltage pre-amp outputs. When you use a Y splitter, you decrease the voltage going to each component, which is why the speakers get louder when you unplug the other one. When you take an already low voltage line out signal and cut it in half by splitting it to 2 different copmonents, it's probably not enough for your amp to make up for even if you turn the gain up all the way.

Assuming you have an aftermarket head unit, you should just run the soundcard to the aux-in of the head unit, and run the preamp outputs of the headunit to the amp. You already said your amp has a low-pass filter so it shouldn't be an issue

Quote: Originally Posted by soundman98

the best way to connect it would be to use the head unit speaker outputs. using just rca cable from the pc would work, only if you were amplifying all of your speakers.

by setting it up the way you have, you will now have 2 volume adjustments--the one on the radio--for the main speakers, and on the computer, the one for the main speakers, and sub. if you ever decide to listen to the radio, or a cd/tape in the radio, the sub will not work.

If he hooks it up like I and others have said, it'll be just as good without the need for a LOC

soundman98 · 07-17-2009, 12:50 PM

Quote: Originally Posted by blazini

That's because most of them (like me) aren't using a headunit. In my case I go directly from the soundcard to my 4 channel amp which has RCA line-outputs, to my subwoofer amp.

You have to remember that a soundcard is meant for home-audio type line-in/line-outs. Car audio equipment has higher voltage pre-amp outputs. When you use a Y splitter, you decrease the voltage going to each component, which is why the speakers get louder when you unplug the other one. When you take an already low voltage line out signal and cut it in half by splitting it to 2 different copmonents, it's probably not enough for your amp to make up for even if you turn the gain up all the way.

Assuming you have an aftermarket head unit, you should just run the soundcard to the aux-in of the head unit, and run the preamp outputs of the headunit to the amp. You already said your amp has a low-pass filter so it shouldn't be an issue

If he hooks it up like I and others have said, it'll be just as good without the need for a LOC

the reason for the LOC is that he said that he does not have any pre outs on the radio, but def. some good points.

digital79 · 07-17-2009, 04:15 PM

So you have 3.5mm split into 2 * 3.5mm, then one of those gets converted into RCA, then RCA goes into the amp RCA?

If yes, then I think that's your issue. Since you are bridging, and I don't see any bridge switch on your amp, you need to provide red/white amp's inputs with signal only from PC's one RCA (red or white only), not both. So you need to get one more RCA Y-Splitter, split one into two plugs, and then plug those into both of amp's inputs.

http://www.worldofcables.com/store/c...UD-1500-01.jpg

Before you do that, just check if each channel is working, by attaching sub to left, then right output only, all changes of course with power off.

Your gains seem to be at zero?

thewizard · 07-18-2009, 10:23 AM

If you are retaining a head unit than you would be crazy to do what has already been said. Run the car PC into the head unit's aux-in then use the H/U's outputs to the amps/speakers. This is how my system is wired and I love it. I can still use the remote control, H/U's radio tuner, and all my existing digital processors, line drivers etc. You can also use the H/U's on board crossovers if it has them.

Toxic0n · 07-18-2009, 02:38 PM

Turned out to be a defective amp. I replaced it with an MTX one and all is fine - sounds great. Unfortunately, my headunit does not have sub pre outs so I will have to live with independent volume adjustment for now. As long as I don't change the volume on the headunit (which is in my glovebox anyway) and only control the volume through the PC, it sounds fine. I am going to get a different headunit soon and run the subwoofer from that. Thank you everyone for the suggestions.

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