power cable alongside usb? OK?

**zaxxon** · 09-07-2004, 09:33 PM

Quick question, sorry if this is a FAQ, could not find the answer on search.

I am running a 4 guage power cable to the trunk for an amp and a epia-M PC. I have the interior apart to gain access to the area under the console to run wires. It's an easy shot through the console to the trunk for all of the needed wires, but that puts the 4-g alongside a usb cable, a video (VGA) cable and a serial cable.

Is that a potential noise problem? Should I pull it out and run it along the door sill? I was going to put the speaker wires to the doors along that sill as well, but if I had to I would put those through the console as well....

Anyone been there/done that? Any opinions appreciated.

**NovaKane** · 09-07-2004, 09:45 PM

I think you will hit a little bit of noise running it that way. But I am not an expert on the subject. Think about it this way, even with shielded RCA's for car audio you run the wire's seperately, because you will pick up engine whine and other noise...so what should this be any different.

**rando** · 09-07-2004, 09:57 PM

The noise introduced by the power wire might increase your bit error rate on the serial and USB lines but ultimately this probably will not manifest itself as any kind of audible noise -- assuming that's what you mean. I presume you don't have any audio running over your serial bus. If you are using a USB sound card, then it's possible that noise on the USB bus could result in pops and clicks in your music...assuming the sound device and computer don't implement some form of reliable end-to-end tranmission protocol (and they probably do).

Your video cable and pre-amplfied RCA audio lines should be run away from the power wire (and everything else if it's possible). Noise on these WILL be heard in your audio and/or seen on your video display.

**zaxxon** · 09-07-2004, 11:36 PM

Thanks for the advice.

I decided to pull the power wire and run it down the right sill. I really have no choice but to run the serial (OBD2), USB (touchscreen), pre-amp level RCA's, and VGA (lilliput) through the console. I am going to run the RCA's on one side of the console, and everything else on the other (and cross my fingers).

I have to run speaker wire to the front door speakers as well. I can run those down the left sill, but they have to be the same length correct? I trust it's not a good idea to coil the extra for the short (left) side. That is going to be a long run as the amp is in the right corner of the trunk.

Also, I did find more info on this when I searched a little more using "noise" as a keyword...

**rando** · 09-08-2004, 12:15 AM

The speaker wires don't have to be the same length but you will get a marginal improvement in sound quality if they are -- unless you're an audiophile with high end equipment, you probably won't be able to tell the difference. Also noise is not a problem on the speaker level wires since their signal level is so much higher than any introduced noise. As long as you don't coil the wire tightly or around an iron core, it's probably ok if you loop the speaker wire.

If you pickup interference from your RCA run, you can always switch over to a USB sound card. The benefit of doing so is that you can then place the sound card right next to your amp and run very short (inches) RCA cables. Essentially you keep your sound digital right up to the amp -- a very good thing!