Sound quality of running 3.5mm into RCA and then outputting to subs?

AznArkitekt · 10-12-2006, 02:52 AM

My setup is near complete, aside from the fact that I need to integrate my carputer (a gateway laptop) into my sound system. Right now, I am running a Pioneer DEH-P6400 head unit into a 500/1 JL Audio amp with 2 12s. I intend to load up my carputer with mp3s and use it as both a system for my front end (most likely going to be streetdeck) as well as a storage device for my music. So heres the situation: The laptop has a single 3.5mm output jack. The HU has a wiring harness (which I've already wired into the car), a low density output (RCAs running to my subs), a front output (not sure if I need this at all) and most importantly, an IP-Bus input (don't have the adapter yet but it's in the mail on the way here).

My original intention was to simply run a Y adapter 1 phono plug to dual phono (RCA) into the IP-Bus connector. Then I realized that sound quality would probably be horrible so I started looking for an external sound card for the laptop through which I could connect to the IP-Bus. Searching around on forums, I came across this post which has probably been by far the most helpful: http://www.mp3car.com/vbulletin/faq-emporium/32430-how-get-sound-pc-car-stereo-amp.html It covers nearly all the bases and answered a lot of my questions BUT I couldn't find any info regarding how the subs would be affected if I was running a source from 3.5mm (laptop) to RCA input (HU) and then outputting the low density (into the amp). The second diagram on the post is as close to my situation as it gets, aside from the fact that I will only have one 3.5mm jack if I don't get a sound card. Also, it seems a lot of people have a lot of bad things to say about converting from a single 3.5mm jack into RCA outputs so I'm a bit concerned about that.

If anyone can explain my situation to me a bit better than I understand right now, I would greatly appreciate it as I'm confused out of my mind on what I should do. I've done plenty of searching on the car audio section and can't seem to find a consensus. It just seems that everyone has a different opinion on what is good and what is not. If I could just get an explanation as to how one set up is better than another, that would help a great deal. I'm guessing the obvious answer to that question is getting a new external sound card as I've read many people have done but yet some people feel it is completely unnecessary. Thanks! (btw, I searched 'laptop' under the car audio forum and came up with nothing :-/ not sure what kind of key words to search for in my situation so I just read anything that was somewhat relevant)

mhornnt · 10-12-2006, 03:08 AM

*EDIT
Looking back at this response now its longer than I expected so I'm sorry if its a bit long winded. To sum up, if you've got a line out on your laptop, go ahead and proceed as you plan too, if not, beware the quality may not be what youre expecting. Keep reading if you want more detail
*EDIT

Alright, my first question for you would be this, does your laptop have an actual "line out" 3.5mm output, or just a headphone 3.5mm output? (Ive seen very few laptops that have anything other than a mic in and a headphone out) I only looked briefly over the link you included, so I'm not sure how much or if it was covered, but if you're going to use the 3.5mm out straight to your head unit with the RCA adaptor, you need to make sure its a "line out" and not headphones. If it is indeed a line out you're all set, and the sound will be good, including what is then run to your amp/subs. If however, it is instead a headphone output, you're going to run into problems. The reason being, the aux in on your head unit is expecting a line level, or basically unamplified signal, which it will then process and output to your speakers amp etc. If you go with the headphone output however, you have a signal thats already been amplified, and while yes its possible to just lower the volume to mimic what a line out would be providing, at least in my experience this tends to result in much lower quality. Hope this helps

AznArkitekt · 10-12-2006, 03:51 AM

ahhh, that definitely helps a lot. so that's what a line out is for eh? I've always wondered what it was since I was a little kid haha. my laptop is sittin in my car at the moment and I'm not sure if it has a line out. I'll look into that tomorrow and post my findings. thanks again! and about it being long winded? I'd much prefer lengthy replies that provide explanation as opposed to short answers, just because I'm trying to learn how things work as I go about my project, rather than follow instructions without understanding how my setup is actually working. thanks!

AznArkitekt · 10-12-2006, 10:31 AM

Well, sadly it looks like my laptop carputer only has a headphone output and mic input...so I guess that means I'm going to need an external sound card if I want good quality?

Jahntassa · 10-12-2006, 10:47 AM

On most computers, the output is labelled as a 'headphone' output. Traditionally any 'output' on a consumer device is considered 'headphone' out if the volume is variable (I believe), whereas 'line-outs' are usually fixed in volume. I think most soundcards will label their output as a 'headphone' out.

Though yes, your quality will improve if you have a USB / PCMCIA soundcard solution with an actual line-output.

AznArkitekt · 10-12-2006, 11:25 AM

I searched for PCMCIA sound cards on ebay and pretty much the only thing that came up was soundblaster Audigy cards. Under the specs, it says that theres a 3.5mm jack for ("Line in/microphone in/optical in") and a 3.5mm jack for ("Heaphone jack/Optical Out")... is it pretty much grouping the headphone jack and line out as the same output? I'm not sure if this is what I'm looking for mhornnt noted that I need a solitary line out and not a headphone out.

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