DracoDan

I recently finished up my JeepPuter and got it installed in my Grand Cherokee. I had decided to go with an eeepc laptop to power everything, unfortunately it only has a microphone input, and no line in input. I have the line out running directly to an Infinity 4+1 channel amp. Audio playing from MP3's or anything else on the computer are loud and clear, but the XM input I have to max the microphone volume to max and enable the microphone boost to get it to the same level as everything else on the system. This makes the already crappy XM quality almost unbearable.

I'm trying to avoid using a seperate USB soundcard since that would mean I would have to use a USB hub in the back (most of my USB stuff is in a hub behind my "deck"). Are there any quality preamps that are very small and could bring the output of the XM up to microphone levels? I don't know if it made a difference, but I had to install a ground loop isolator between the XM and laptop to get rid of engine noise, even though their on the same ground.

Thanks
Dan

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rgarjr

What kind of XM radio u have?

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DracoDan

It's the standard MP3car XM package

hailrazer

Mic inputs are mono and you need a stereo input.

Might want to go with an external USB soundcard.

rgarjr

The thing with pre-amps is that it can most likely bring some noise or hum in. Yeah connecting the audio to the mic in isn't a good thing.

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DracoDan

I thought this as well, so I tested it with a single channel at a time and determined it is in fact stereo sound. The sound is based on the intel HD audio, and the app that it comes with even has a place to choose between line in and microphone in, but it doesn't make a difference on how loud the audio is.

DracoDan

My post at Eeeuser for cross referencing:
http://forum.eeeuser.com/viewtopic.p...223262#p223262

GizmoQ

Its unfortunate that you're experiencing a ground loop. I had the same problem with my XM Commander when I first installed it. I tried several methods to rid myself of the noise including what you've already tried, i.e., grounded together, ground loop isolator, grounded XM PCBoard to Computer and hedf unit, etc. What finally worked was moving the unit and shielding the unit's PCBoard and RCA cables. Yes the XM PCBoard is picking up RFI and its compounded when you use the RCA out (I patched into my FM antenna and used the FM modulator and no engine noise was discernible).

My recommendation to you is get the external sound card with a decent line in. If that's not an option then bite the bullet and buy some high-end shielded RCA cables (I think I paid $32/pair) and try relocating the XM box to several different locations to find one that reduces the noise picked up.

All my personal installs have been with TabletPCs and until the most recent an external sound card was out of the question so like you I used the mic in for XM. Out of the three different Tablets I've installed, the output of the XM has always overmodulated (too loud for) the Mic line...hmmm.

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DracoDan

The ground loop isolator actually completely took care of the ground loop noise for me. I don't have a head unit, I'm going straight from the XM box to the computer thats 8" away using a 1m cable. The only idea I have is that the ACC line has a slightly different voltage than the line directly off the battery and thats what's causing my issues. The ground loop isolator might just be masking the real problem. I just can't figure out what the deal is with the microphone input.

DracoDan

up to the top in hope for help.

DracoDan

^^^

DracoDan

I noticed something weird today after I had the battery die on me and my laptop was abruptly shut down (another issue I'm dealing with). As the system was coming back up, the line input was open and the XM volume was very loud and clear. As I was being logged into windows (I dont use a password for my carputer) the volume went from loud to the low volume that I'm used to being stuck with. After messing around with the microphone test, I discovered when the test opens the "microphone" input to do the testing, the volume is loud, almost too loud. As soon as the test is complete however, it again goes back to being low.

I now know that the problem is entirely software related, since I've already seen all the hardware perform as intended (during boot). I have downloaded and installed the latest realtek drivers and disabled all equalizers to make sure they weren't messing with the signal.

My only ideas I can think of in this point is either a registry setting that limits the playback volume. Another possibility is that the driver for the XM controller is telling it to turn down it's ouput level (I don't know if thats controllable or not).

I was about to buy a new USB sound card, which would require some major replanning to get enough ports by the laptop (I hate USB hubs). After seeing this work, I am convinced that new hardware isn't needed.

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