View Full Version : 2 computers & 1 set of speakers?

7th December 2000, 21:51
I currently have 2 computers, 1 set of klipsch promedia 4.1's.

Problem is that I have to find a 3.5mm switch that supports 2 3.5mm in and 4 out (2 for each computer)

Currently I am using splitters. The problem is that when both computers are on, the volume is cut in half.

Anyone able to address this issue?

7th December 2000, 22:01
Are you refering to Y cables to combine them?

7th December 2000, 22:07
Yeh, I'm using a Female to 2 Male Y Cable

7th December 2000, 22:23
Could always use one speaker for each system. http://forums.murc.ws/ubb/smile.gif

What you need is a mixer, you can pick up a dual opamp and a couple of resisters and caps and toss somthing together in an afternoon. Or quad op amp for more speakers. Or simply route both computer inputs into a stereo and run the outs to the computer speakers.

7th December 2000, 22:26
You have DC current leaking from one or both cards output(s). When this happens the curren is backfed into the cards and offsets the bias, thus potentially reducing the output levels.
Fix, place a 10mf non polar capacitor series with each signal wire (4 total) and this should cure the problem.

8th December 2000, 00:30
If you're willing to sacrifice something you probably aren't using anyway, try this:

Pipe the line-out of the computer you want sound from into the line-in of the computer that has the speakers connected, and leave the line-in selected in the mixer. Granted, this will only get you stereo sound, but there will be minimal loss in signal.

Resist the urge to make your own splitter: unless you know the line level impedances of the soundcards, you could damage one or both of your soundcards (Including the way they are currently connected).

Hooking Caps in between your splitters will fix your problem - sort of. The disadvantage here is that the entire "Q" of the system is changed, and without knowing the input impedances of the cards, it's really a crap shoot...it may sound muddy, or tinny, or may sound normal: you might need to experiment with higher or lower valued caps...

As mentioned by Himself, an inexpensive mixing board is also a viable option.

8th December 2000, 05:03
You're right, Greebe. :-)

The uncertainty, that was the rub with me. Using a Cap as a filter, (a cap in series with the circuit) creates a first order highpass crossover. The crossover point, though, is unknown, unless we know the exact impedances involved.

I grant you it is not a big deal, but still, the uncertainty is bothersome, and your lower frequency sounds will suffer some (A bummer if you happen to have a subwoofer). An electronic mixer generally has impedance-matching circuitry that negates these disadvantages. (Side Note: My Car Stereo uses all active crossovers :-) )

8th December 2000, 06:54
Thanks for all your feedback, a lot of this is beyond my knowledge of electronics, so a bit more detail would be appreciated.

- himself, I'm not experienced in constructing electronics, is there an inexpensive mixer like this available to consumers?

- greebe, you say that placing 10mf non polar capacitors would solve the problem. Which wires would the be placed on? The output wires from the computers to the control, or on the speaker wire out to each speaker? If on the speaker wire, the subwoofer won't benefit from the capacitors...

-multimedia man, so I would splice into the Y splitters and place the capacitors there?

Overall, I'd prefer the method that has the least amount of signal degradation. Ease of installation might also play into it...

[This message has been edited by isochar (edited 08 December 2000).]

8th December 2000, 09:57
Greebe, anyway you could check the radioshack.com website and show me a URL to the capacitor you're talking about?

8th December 2000, 12:52

Check out this FET mixer, the nice bit about this one is that you don't have to fudge a +/- power supply. You could probably get that down to +5V and run it off the power in your computer.

Good source of parts is http://www.digikey.com/

8th December 2000, 14:14
The crossover point, though, is unknown, unless we know the exact impedances involved
I know the relative impedence of the circuit and thus answered with an appropriate componet where it's crossover point is below audible limits (ie <10hz).

isochar, these (http://www.radioshack.com/product.asp?catalog%5Fname=CTLG&category%5Fname=CTLG%5F010%5F002%5F016%5F001&product%5Fid=900%2D2085) will do just fine. http://forums.murc.ws/ubb/smile.gif

You can add the caps to the Y cables by severing the center conductor and connecting each cap lead to each of the now open center conductor leads. (series circuit). The shielding wire (ground) should have the outerjacket stripped back ~=>1/4". Then lay ground wire braid back over the outerjacket. Next, insulate (wrap) the exposed wire connecting to the cap(s) with electrical tape or with heat shrink tubing (prefered).

After this is done you can wrap the entire area in aluminum foil (Yah I know, but it'll work and is cheap! http://forums.murc.ws/ubb/smile.gif connecting the layed back shield (ground) braid at both ends. Wrap in electrical tape and your done. http://forums.murc.ws/ubb/biggrin.gif

8th December 2000, 15:31
I just ordered a dozen capacitors from radioshack (I ordered extras cause they're so cheap I didn't want to spend more on s/h than on the parts themselves http://forums.murc.ws/ubb/smile.gif)

So I'll message you guys when I receive them...

8th December 2000, 16:35
MM, Typical linein impedence of just about every known audio IC is at least 10k ohm (including powered speaker inputs). The output is low (under ~100 ohms) and so connecting a higher impedence doesn't effect it (do the math). Adding the caps will change the Q of the system per se, by inducing a phase shift of 6dB/octave. Now for the flip side of the coin, "Q" is totally negated unless the "system" is of a totally DC design (which it is not). Hence this effect is totally undiscernable and acceptible in a computer sound system (and 99.5% of all sound systems made).

16th December 2000, 10:49
I got my capacitors in. Greebe was gonna help me, but I think I used up all my free technical support time with him. http://forums.murc.ws/ubb/smile.gif

Could someone help me with modifying my Y splitters with the capacitors?


16th December 2000, 11:00
iso, U used up the tech support from me because of your pride in nV's business practice and were reveling in it! I hope you see the the light before you actually use that business degree, because it's grossly unGODlike, unethical and prevertedly sickening! http://forums.murc.ws/ubb/frown.gif

16th December 2000, 12:07

i'd like to say i'm sorry for my personal opinions on how the world works, but as an educated individual i believe no one should ever apologize for opinions. (unless sexist, racist, speciest, etc.)

if you want to start a discussion on business practices, i guess we should throw it in the soap box.

Here: http://forums.murc.ws/ubb/Forum9/HTML/001197.html

for the sake of this post, i'll reiterate my request for any help with modifying the splitter.


[This message has been edited by isochar (edited 16 December 2000).]