Combine two line level audio signals?

[Noozer]

I want to combine the line output from to PC's into a single set of
speakers. I know that reversing a Y cable is probably a bad idea. What's
the simplest way to do this properly?

 

[jasen]

On 2007-01-21, Noozer <dont.spam@me.here> wrote:

I want to combine the line output from to PC's into a single set of
speakers. I know that reversing a Y cable is probably a bad idea. What's
the simplest way to do this properly?

a couple of 1K resistors will be enough to protect your soundcard's outputs
from each other.

.-------------------------------------------------------------.
| This is an ascii schematic, if the diagram appears garbled |
| try switching to a fixed-pitch font (courier works well) |
| pasting it into notepad works well on ms-windows. |
| in google groups selecting 'fixed font' (top right of page) |
| or view source (options) work too. |
`-------------------------------------------------------------'

fixed channel combiner
.----- right left
Sterio jack plug | | | / |\ /|
_ _ ____ ___________| | | / | \/ |
/ ~-_/ ## | ## | | / | / |
/ `-----------------------| / |/ |
\ _-------------------------------/ common | |
\_-~ \_##____##___________-----------------------------------
| |
| |
`-----'
common 1 ---.
|-------------- common out
common 2 ---'

left 1 --[1K]--.
|----------- left out
left 2 --[1K]--'

right 1 --[1K]--.
|---------- right out
right 2 --[1K]--'

If you get hum from that something more elaborate is needed

I've not seen cables like this for sale anywhere so you'd have to make
them. the cheapest way to do a reasonable job is probably to solder
the resistors in-line and use heatshrink to insulate and strain-relieve
the joint

--

Bye.
Jasen

 

[Noozer]

jasen wrote:

fixed channel combiner
.-----  right  left
Sterio jack plug          |     | |     /              |\  /|
_    _  ____  ___________|     | |    /               | \/ |
/ ~-_/ ## |  ##                 | |   /                | /  |
/          `-----------------------|  /                 |/   |
\    _-------------------------------/       common     |    |
\_-~ \_##____##___________-----------------------------------
|     |
|     |
`-----'
common 1 ---.
|-------------- common out
common 2 ---'

left 1 --[1K]--.
|----------- left out
left 2 --[1K]--'

right 1 --[1K]--.
|---------- right out
right 2 --[1K]--'

Thanks! Thats the information I needed to know.

 

[Mark Aitchison]

Noozer wrote:

I want to combine the line output from to PC's into a single set of
speakers. I know that reversing a Y cable is probably a bad idea. What's
the simplest way to do this properly?

Let's see.. you have two PC line outputs (normally these are stereo, so
2x Left and 2x Right) and you want to have one set of (must be)
amplified speakers for both computers. Okay, you need two stereo 3.5mm
(1/8th inch) plugs to match the soundcard outputs, and four resistors of
about 4.7 kilohm (or anywhere between 2k and 10k, so long as they are
all the same), plus one stereo 3.5mm socket (or whatever your amplified
speakers need to plug into), plus some cable. You might be able to get
all of this other than the resistors already made up in a Y cable like
you suggested then snip it in two places, in the line of each of the two
cables going from the 3-way join to the plugs that go into the PCs
probably if your Y cable looks like I imagine it.

The important thing is to put a resistor in series with each line output
(two lines, each with L & R outputs means 4 resistors), with the other
ends of the resistors joining to go to the single line (L or R) to the
amplified speakers. If they aren't amplified speakers you won't get any
sound, by the way. If it is a single (mono) amplified speaker you can
mix them all down into one channel instead of Left & Right. If you need
more help let me know (I didn't try drawing a circuit 'cause I don't
think ASCII artworks are going to make it clear enough).

Mark A.