Can you hook up two audio sources to one speaker system?

Discussion in 'Playback Devices' started by JamesAH, Sep 11, 2004.

  1. JamesAH

    JamesAH Agent

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    Will they both come through fine, messed up or will the system blow? I want to hook up a music and game console source to a simple Klipsch 2.1 system. Can I do this with a simple combiner from Radio Shack?

    Thanks.
     
  2. Brian Fellmeth

    Brian Fellmeth Supporting Actor

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    Just plug the game out sound RCA's to one of the inputs of your receiver
     
  3. SimiA

    SimiA Second Unit

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    You receiver should have multiple inputs to connect your audio sources.
    Vb
     
  4. Wayne A. Pflughaupt

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    I think James may be referring to Klipsch computer speakers. Perhaps he’ll drop back by here and clarify,

    Regards,
    Wayne A. Pflughaupt
     
  5. Patrick Sun

    Patrick Sun Moderator
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    You might want to get a 4-in-1 A/V switcher (around $20 at Wal-Mart, Radio Shack, etc).
     
  6. JamesAH

    JamesAH Agent

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    Indeed I am refer to the computer speakers. I do not have a reciever.

    I do not want a switch either, I want both of them to come through at the same time.

    Thanks.
     
  7. alan halvorson

    alan halvorson Cinematographer

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    This seems a strange request. All I can think of is a mixer. I don't know if there are any software versions but there are plenty of hardware versions in any musicians store (and maybe a cheap one at Radio Shack).
     
  8. RomanSohor

    RomanSohor Second Unit

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    don't they sell headphone splitters at Radio Shack? Just get a Y adapter, with two female 1/8" jacks at one end and 1 female 1/8" jack at the other end (they might only sell one with 2 females and 1 male, so you might need an adapter for it, too) but if you tell the guy at radio shack that that is what you need they can definately find something for you.
     
  9. JamesAH

    JamesAH Agent

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    ^That's my plan, but will it harm my stereo?
     
  10. Wayne A. Pflughaupt

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    No.
     
  11. David_Rivshin

    David_Rivshin Second Unit

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    This topic has come up a number of times (check the cables&tweaks forum), but here's the long and short of it:

    1) using a splitter in reverse is not the best thing in the world. The output of one component will drive the output of the other component, and vice-versa. Won't break the speakers, but not the best for the sources or for sound quality.
    2) What you want is a device called a mixer. You can build a simple one with some resisters, an op-amp, a power source (batteries work fine), and the necessary box&connectors. You can buy one, but they tend to be more expensive than you probably want, cheapest I can think of is perhaps the Behringher UB series for around $50.
    3) You can build a poor-man's 2-channel mixer with a splitter where you put a resister inline with each input. This will largely prevent the problems of just using a splitter. Note, this doesn't give you any independant volume control unless you use reostats for the resistors.

    Hopefully I'm remember everything correctly, someone will probably correct me otherwise [​IMG]

    BTW, I have Klipsch Promedia 2.1 speakers for my computer, and the control box on mine has an input jack for a second source, intended for things like portable MP3 players. The control box applies a 6dB boost the the aux input, and then mixes it with the main ("computer") input. If yours has the same then that will probably solve your immediate problem.

    Hope this helps,
    -- Dave
     
  12. JamesAH

    JamesAH Agent

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    My 2.1 system did not come with a control box. The volume and sub controls are on one of the speakers.

    Do you have a link to instuctions to build a mixer?
     
  13. JamesAH

    JamesAH Agent

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    bump
     
  14. David_Rivshin

    David_Rivshin Second Unit

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    On my Promedia speakers the volume control is on a little "pod" which is attached to one of the speakers. On the right hand side there are two 1/8" jacks, a headphone out and an aux in. You can actually take the pod off and move it to another speaker (or anywhere else) with alittle bit of effort.

    Disclaimer: I'm not an EE of any kind, let alone an analog EE, so take everything I say past here with a big grain of salt [​IMG]

    To build a "poor man's mixer" just take a splitter, and cut each end open. On both the right and left signal wires in each half install a resistor. Leave the shield/ground wires unmolested. I'm not sure the best resistor value, but I'll guess 10KOhm would be good. Max voltage would be around 2V, so you don't need high-power resistors. As splitters and resistors are cheap, as long as you already have a soldering iron you can get away with just a few $.

    Building a real powered mixer is more involved. Basically you want to build a circuit called a summing amplifier. I'm no expert on them, although I did start (never did finish) building a small mixer myself a few years ago. Try a google search for things like "summing amplifier mixer". A quick search found me this page which has a basic mixer diagram on it: http://wiredworld.tripod.com/tronics/mixer.html
    For a stereo signal you need two such circuits. I've seen more involved circuits with some capacitors (to reduce noise, I believe). If you want to be able to modify the level of each input, change the input resistor to a variable resistor. Dial type reostats are easy to come by and cheap, sliders are hard to come by and expensive, but look slicker.
    For op-amps I think LM77's are generally recommended. Burr-brown has some nice ones as well. As always you can look up specs online and compare. Also, since the standard op-amp circuit will invert the signal, you may want to add another op-amp per output channel to invert it back, but that's not required. For a power source I personally prefer a pair of 9-volt batteries, to give -9V - ground - +9V, which is more than enough swing to a 2V line-level signal, and cheap.

    Past the circuit itself, you just have to attach connectors to the input and output, and wire it all up in a box of somekind. You should be able to get all the necessary parts from someplace like digikey or MCM.

    Just found another good page: http://www.mitedu.freeserve.co.uk/Ci...dio/6ipmix.htm
    Note that it's for a microphone mixer, so the first bit of each input channel is a mic pre-amp which you can ignore.
    I'll also admit that the cap and resistor values are a black art to me, and I have no idea how to determine the best ones. I just follow what everyone else says [​IMG]
    Oh, and this looks like a must-read: http://www.forsselltech.com/summing%20buss.htm

    Hope this helps. It's not a small undertaking, but if you're handy with a soldering iron and have basic skills with electronics you should be able to pull it off. Of course by the time you're done adding up part costs you might not be too far away from just buying something like a UB802 and being done with it [​IMG]

    -- Dave
     

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