Newsgroups: rec.audio.tech Subject: Re: Stereo headphone jack to mono RCA audio References: <[email protected]> [email protected] writes: > I want to connect the stereo headphone jack on a laptop computer to a > mono RCA audio jack on a television and get both the R and L sound from > the laptop mixed to mono out of the television speakers. Also, the > laptop and television are about 20 feet apart. What is the right way to > do this? The right way to this is to take 6 feet 3.5 mm stereo plug to two RCA connectors cable. And then add the following circuit (you have to build it yourself, no recommendation where to buy ready maade) between the two RCA connectors and one RCA connector on the TV. http://www.epanorama.net/circuits/linesum.html To build this circuit you need three RCA connectors and two 10 kohm resistors (R1 and R2). The resistors connect the audio signals (center connector) from inputs together to from one output signal. You can see the wiring details in the figure below: INPUT 1 -------\/\/\/\---+ ---+ R1 10K +------------ OUTPUT | | +---- INPUT 2 -------\/\/\/\---+ | ---+ R2 10K | | (shields) | +---------------------+ When you have connected the audio lines together using the resistors, then connect the connect the connector grounds directly together using short piece of wire. Now you have made a nice one channel mixer circuit which can mix together two line level audio signal sources. > Regarding the 20 foot cable I will need between the laptop and the > television, I was thinking I could connect two 10 foot RCA cables > together to get the distance. It is possible. But it should not be too hard to find ready made 20 foor cable. I can myself find 10 meter cables from computer and audio shops without problems... Hooking up two RCA cables after each other can work also work, but with low quality cable connectors and/or RCA female-female adapters this joining of two cables can be unreliable. > I know that for RCA composite video this > would not work since the cables are designed to have a specific > resistance (I think), so connecting two in series would double the > resistance then it wouldn't work correctly. Joining two cables will work for composit video and other video signals as well. The video cables are designed to have a specific impdance for the high frequency video signal travelling with the cable. This cable impedance is something diffent than the resistance you measure with a multimeter. When you have a video cable that has 75 ohm impedance is always 75 ohm for the signal no matter how long the cable is. When you take 75 ohm cable from the cable spool to make cable, you can cut any length of the cable and the results is 75 ohm transmission line. And you can join together two pieces of 75 ohms cables, if the connection is done well it is practicallyu same as one long pice of 75 ohm cable. > But will connecting RCA cables in series work for audio? Connecting RCA cables in series will work nicely. No problems as long as you do the connection reliably (so that the cables make good reliable connection). -- Tomi Engdahl (http://www.iki.fi/then/) Take a look at my electronics web links and documents at http://www.epanorama.net/
