Computer sound 5.1 hum/hiss with powered speakers

Hi all, first post!

This is a "how do I wire up my balanced speaker inputs to a computer sound card" question.  It works, with RCA cables, but has some hiss and hum.

I have a Windows PC with an internal Creative SoundBlaster X-Fi Elite Pro 7.1 surround sound card (http://support.creative.com/kb/ShowArticle.aspx?sid=10571) that's been driving a Creative Gigaworks S750 7.1 surround speaker setup (http://support.creative.com/kb/ShowArticle.aspx?sid=4808) for years, and recently the amp/sub died (while physically unplugged from the wall in preparation for a Big Storm moving through town, believe it or not).  I decided "7.1" was a bit too much for my day-to-day music listening, Skype-ing and occasional gaming, so I replaced those speakers with five stand-alone KRK Rokit RPG2 6" powered speakers (http://www.krksys.com/krk-studio-monitor-speakers/rokit/rokit-6.html) instead.  No sub yet; might not need one at all as these speakers deliver plenty of bass for my non-bass-loving ears.

The sound card has three 1/8" TRRS (really, 4-wire tip/ring/ring/sleeve) line-out jacks that I haven't been able to find adapters for, but I have the special TRRS-to-TRS 1/8" cable the speakers came with, which I'm not using now anyway.  This cable is totally unbalanced, having 1 TRS jack for Front L/R, 1 TRRS jack for Rear L/R and Side R, and a second TRRS jack for Center/Sub/Side Left.  Fortunately those 4-wire TRRS jacks also work with 3-wire TRS plugs, for when you want to use less than 7.1 speakers.

I bought three 1/8" TRS (male) to 2xRCA (female) splitters and plugged them into the back of the sound card (tight fit, but they fit).  I then soldered 5xRCA (male) plugs onto the end of five of the original speakers' wires, giving me plenty of male RCA -to- male RCA wires.  Fired it up, figured out which cable goes with which speaker, and it works beautifully.  Sounds great.  Except for the constant 60Hz hum and hiss which doesn't vary much as I turn the volume up or down.

Now, these KRK Rokit RPG2s *do* have balanced XLR and TRS inputs as well as the unbalanced RCA, one of which I think I need to be using.  I'm using the RCA jacks now simply because that's the kind of cable I have.  Must admit these wires are about 7 years old, came packaged with the previous speaker system, and certainly aren't professional grade (think Walmart speaker wire).  What's weird is the hum/hiss is barely noticeable while the computer is powered up and running, but when it shuts off is when the noise becomes a problem.  It's not precisely at the moment when the PC actually turns on or off, but rather the hum/hiss disappears *during* start-up and re-appears *during* shut-down; I guess that's when the sound card drivers are loaded and unloaded, or initialized, or something.  ALSO everything is plugged into a total of 3 Tripp-Lite power strips about 4 feet long with 10 or 12 electrical sockets on each; those are plugged into two APC battery back-up units; and those two are plugged into the same dedicated wall socket used only by equipment in this room.  It's a home office, so there are microwaves and tons of other typical household electrical appliances throughout the house, but I had a dedicated 30A electrical circuit run especially for this room.

I think my hum/hiss problems are coming from either these cheap 2-conductor RCA speaker wires, or that the wires are routed underneath my computer desk right next to a power strip, several small power bricks (for USB devices, cell phone charger, network router, etc.), a foot away from two LCD screens, and lots of other typical computer peripherals like two PCs, a Mac Mini, a "Tube MP" mic preamp, two phones, stand-alone NAS, lots of network/power/data cables, a couple of little bubbly Zen water garden... things, and more.  It's a typical computer desk with lots of stuff plugged in.

SO, the questions: 1) Do you think the unbalanced RCA cable is the source of my hum/hiss, or its being routed along-side lots of power cables and power brick adapters?  2) Should I replace them with RCA-to-TRS or RCA-to-XLR?  3) Somehow I'll need to convert the 2-wire RCA output from the sound card to a 3-wire TRS or XLR plug; will the typical RCA adapters work?  4) Should I be concerned about "balanced" wires or "shielded" wires?  5) Should I think about moving the power connections for just the five speakers to their own power strip and/or wall socket or a separate circuit?

Thanks in advance!

Thanks Max,

Shielded cables aren't cheap, so what I was getting at was whether to look at shielded RCA cables or shielded TRS/XLR cables with some kind of adapter to get from my computer's RCA output to TRS or XLR.  Sounds like from your reply I need to figure out how to run the speaker cables away from the various power wires too.

Thanks JRG1990,

I'll look further into a ground loop isolator, but all I've seen so far handle a single channel at a time.  I'd need five of those, plus maybe another one if I add a subwoofer.  I wasn't aware I was already splitting a signal, though.  How the signal goes is from unbalanced computer sound card to balanced-capable speakers (not the other way around), but if running balanced TRS or XLR cables won't fix the problem, then I'll save the dough and skip it.

Thanks JRG1990, that's the kind of answer i was looking for.  I have yet to find such a thing as "shielded TRS" cable, and I didn't know whether I should be looking for "shielded RCA" or just TRS (which is inherently balanced).  Still, the first problem is that my computer's sound card spits out its signal on 5 RCA jacks.  I think hooking those up to an RCA-to-TRS (not RCA-to-TS) adapter with pins 1 and 3 connected, then running the balanced TRS cable to the back of the speakers would solve it.  Is that right?  I know not all RCA-to-TRS are built like that, but this one evidently is:  http://www.amazon.com/Monster-MCL-FRMST-Single-Adapter/dp/B000HHLUCI/ref=sr_1_9?s=electronics&ie=UTF8&qid=1302291467&sr=1-9.  At $15 a pop, and I'll need 5-6 of 'em, plus the TRS cables, I'll keep looking.

Sounds great, thanks!

MadMax, JRG1990, and others,

Thanks again for your advice.  I went out and picked up 2x 25' and 3x 15' shielded RCA cables: http://www.amazon.com/gp/product/B003FVX9FO, plugged them in, and WOW PRESTO BINGO VOILA the hum and hiss are gone!

FWIW I first tried running them along the existing cable spaces built-in to my computer desk (which are unfortunately alongside all those 120v power cables, transformers, etc. as previously mentioned), but figured I'd have to just lay them on the floor if that didn't do the trick, but it did.  No more hiss and hum!  With both everything powered up and cranked up, and also with the computer totally shut down, even my young kids could barely hear anything with their ears held up to the speakers.

So hat's off to you guys for saving me lots of time, effort, and money looking into a balanced TRS or XLR solution.  Those shielded RCA wires seem to be working just fine!

(That particular brand, too -- "Mediabridge Ultra Series" -- has lots of glowing reviews for their price vs. quality on Amazon.com.  I'm not advertising; just a very satisfied customer is all.)