Stereo To Mono?!!

Discussion in 'Home Theater Projects' started by Mark Amayao, Aug 18, 2003.

  1. Mark Amayao

    Mark Amayao Stunt Coordinator

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    Is it possible to convert a stereo signal to mono via some device or accessory? .....

    e.g.

    cd player stereo output -> mono accessory -> mono to amp stero inputs w/ "Y" connection.

    Thanks guys!
     
  2. Chu Gai

    Chu Gai Lead Actor

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    Yes, like the cables found here.
     
  3. David_Rivshin

    David_Rivshin Second Unit

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    Not to correct Chu (I'd never dare to do such a thing [​IMG]), but all I see there are Y splitters... Please correct me if I've missed some device on that page which would be better...

    Technically a Y splitter is not the correct solution. That will connect both the left and right outputs of your device together, causing them to drive each other. If they play almost the same signal then perhaps its not a problem, if they play very different signals you'll likely get output which isn't blended between them very well. Not to mention it's not particularly nice to the electronics (although I doubt any permanent damage will result, someone else would be better to comment on that).

    Basically using a Y splitter (or combiner in this case) to sum a stereo signal has the same problems as using one to sum a signal from multiple devices, or as a replacement for a switchbox. Y splitters are for just that: splitting a single signal into 2 (or more) identical signals. IOW 1 in -> 2 out, not 2 in -> 1 out.


    In any event, the "correct" solution is to use a mixer. You can either get one off the shelf (cheapest is perhaps $50), or you can build one. For your purpose a simple 2-input 0-gain summing amplifier would be fine. You can find schematics for such devices by doing a general search online. I'm sure books on basic analog electronics would have info too, it's a fairly classic circuit.

    Hope this helps [​IMG]
    -- Dave
     
  4. Chu Gai

    Chu Gai Lead Actor

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    I've seen a few approaches to this but frankly haven't tried any. David's approach is one, the Y-splitter approach is another, a variant of the Y-splitter include the presence of resistors, and perhaps a very workable approach is to use software and create a mono disk off your computer. I must say it must be one heck of a device you want to put this through.

    Absolutely you should correct me. For $2 or less it's worth a shot specially when you can return the thing.
     
  5. Wayne A. Pflughaupt

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  6. Mark Amayao

    Mark Amayao Stunt Coordinator

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    I have a client that wants a Niles ZR8630 ..... unfortuantely when he approached me he had already wired his home.

    different zones using either stereo or mono speakers inceiling.

    he didnt factor in stereo outputs of sources ... therefore installed just single speakers not stereo input speakers.

    I was wondering about accessories mainly because he would need an adaptor for all 8 sources! lol .......

    sorry i shouldve elaborated on the application.

    thanks guys
     
  7. Chu Gai

    Chu Gai Lead Actor

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    well that sounds like someone who flunked 8-track audio. heck i'd work a way to put the extra speakers in.
     
  8. David_Rivshin

    David_Rivshin Second Unit

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    Disclaimer: I'm a software engineer, not an analog engineer, so I only know enough about such things to be dangerous. I don't claim to be an expert (publicly [​IMG])

    You all do have a point. If you take a summing amplifier and take out the op-amp you basically have a Y splitter (combiner) with a resister on each input. I've seen some caps to ground also used to remove DC (if memory serves) but I don't think that'd be necessary in this case. Since I don't believe that a 0-gain op-amp would do anything for this circuit other than provide a buffer to the next stage, I think you'd be safe leaving it out. This will also remove the need for batteries or a some other power source.

    The only downside I can think of is that the impedance seen by the next device might be not quite right, but careful choice of the resistors value should make it all come out in the end.

    Some quick notes:
    LO/RO = L/R output
    LI/RI = L/R input
    R1 = impedance of LO/RO
    R2 = resisters in combiner
    Code:
     straight through: 
     LO (R1) --------> LI 
     RO (R1) --------> RI 

    impedance seen by LI and RI is "R1"

    Code:
     with combiner/splitter: 
     LO (R1) ---> R2 - /---> LI 
     |-----| 
     RO (R1) ---> R2 -/ ---> RI 

    impedance seen by LI and RI is:
    2 * ((R2 + R1)/2) = R2 + R1
    impedance seen by LO and RO is:
    R1 + R2 + R2 + R1 = 2 * (R2 + R1)
    which is probably why the signal from LO doesn't push into RO; the path to LI is much easier than the path to RO.

    If I've gotten anything wrong in there someone please correct me. As I said I'm nothing even approaching an electrical engineer, so I have no formal training in such matters.

    PS. does anyone know how to get the
    Code:
     tag to not make everything come out double spaced? wreaks havok with ASCII art...
     
  9. David_Rivshin

    David_Rivshin Second Unit

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    Oh, I almost forgot to talk about this part:

     
  10. Wayne A. Pflughaupt

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  11. David_Rivshin

    David_Rivshin Second Unit

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