Post Subject: Sound Inputs Guide
Posted on: Sep 16, 2008
Adding sound inputs are a simple way to add a little versatility to your box, especially if you've ever wanted to connect external audio sources to your PC. Instead of using an array of cables and converters (which only degrades sound quality), why not use RCA (otherwise known as phono) jacks? Most sound cards nowadays have extra inputs for CD-ROMS, modem speakers and more, so we may as well use them!
Inputs Galore (SB Live! CT4620)
There are 2 simple ways to stick the inputs on your case. You can buy premade boards with 4+ RCA jacks, and bolt the board to the back of your case (You'll have to cut a square out of the case to allow the wires to go thru). Otherwise, if you have an extra slot (and extra slot cover), you can buy just the jacks, and drill out holes for them in the slot cover. That way you can bolt the RCA jacks to the case like you would any expansion card.
RCA Jack Board
Seperate RCA JacksAnalog Inputs
Most inputs on sound cards are analog. They have a left and right channel, and typically a ground for each. Easiest example is a standard CD-ROM cable:
Red: Right Channel
Black (x2): Ground
White: Left Channel
For simplicity I'll use our phono jack board for these inputs.
What we need (for 2 inputs):
Four-position Phono Jack board (Radio Shack #274-322B)
A long CD-ROM cable
That's it! Of course, it'll help if you have wire cutters, soldering iron and (optionally) shrink wrap. For our purposes, the outside pole of the jack is always ground, while the inside pole will carry the audio. So, we'll need 2 separate jacks for each input.
Step 1: Cut the CD-ROM cable in half, and strip a little insulation off each wire:
Step 2: Loop the end of the red wire through the center pole of one jack, and the ground wire right beside it, on the outside pole. Then solder both connections. If you're using shrink wrap, make sure you put it on BEFORE you solder it :)
Only 3 More To Go
Step 3: Now we have to do the same for the last 2 wires on the CD-ROM cable. Solder the white wire into the center pole of the jack, and the remaining black wire onto the outside pole.
Thats one of em! Do the same thing to the last 2 jacks with the other half of the CD-ROM cable.
There We Go Easy Don't You Think?
But now, where do we connect them to? There are a few common inputs:
CDIN(2)(3..) - Obviously for your CD-ROM(s) :)
Aux(2)(3..) - Extra misc. inputs
MIC - Microphone in
TAD - For modems that don't have an onboard speaker, or used for voice capabilities
NOTE: The MIC and TAD inputs are almost always MONO (one channel only)! Only use these if you have a mono source (I have an old FM tuner connected to TAD)
Last thing you need to do is cut a hole in the back if your case so you can mount the inputs. I didn't have any decent cutting wheels handy, so I just drilled it out. Doesn't look all that great, but works nonetheless (besides you only see it from the inside)
More and more cards nowadays include some sort of digital (SPDIF) input. This lets you deliver crystal clear sound from any source that supports it. Most CD-ROMS also have the 2-wire SPDIF output. You can use an SPDIF cable instead of a CD-ROM cable to get better sound from your CD-ROM, but you can also create an adapter to use an external source, like a stereo receiver.
To think this came with a PCChips board!
Unlike an analog input, SPDIF only requires one RCA jack, since all channels run off just one wire. For this mod we'll include one analog input along with the digital one.
What we'll need:
3 Shielded Phono Jacks (Radio Shack #274-346)
2-wire connector (eg from case lights or switches, or SPDIF cable)
4-wire CD-ROM audio cable
Step 1: Measure and drill out a few 1/4" holes. We're going to have an analog and digital input here, so we need 3 holes:
Step 2: Next, mount the RCA jacks in the holes (makes it easier when soldering)
Step 3: Once you've got the 2-pin cable cut and stripped, solder the (non white or black) wire to the outside pole (again, ground). Then solder the other colour to the center pole. I bent the ground pole 45 degrees for a little more clearance when we install the bracket:
Our soldered digital connection
Step 4: Create a analog input using the last 2 jacks (check Back for details)
Here we go, an external digital input, with an analog one to boot:
Completed SPDIF/Analog Inputs
Now all we have to do is connect it to your sound card.
That wraps up this guide. These mods may not be the most innovative on the planet, but it adds a few more features to your 'puter without breaking the bank.
I've done something similar with my HTPC for connecting it to my surround sound.
When I get a chance I think I'll add to more phono jacks conected to the line in, then I can un-mute the line in channel in windows and use it as an extra aux in on the surround sound when the pc is on.