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How to create a muting stereo mixer?

Discussion in 'General Electronics Discussion' started by SethB, Oct 12, 2015.

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  1. SethB

    SethB

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    Oct 12, 2015
    I found out how to create a regular stereo mixer to combine multiple inputs to one output.

    I like this but want to go one step further.

    I wish to only have two inputs. One input is always live, while the second one is open.

    When the second input starts to output a signal, the first input opens allowing the second one to close.

    I first thought, hey a relay would work great. But then realized that audio is an AC current, and not DC, nor is it high enough to trip any relays I have found. What I next thought was to use a power source and capacitor to charge up the relay to a certain voltage, then when the audio line because active, it would put it over the necessary value. However, that would be very hard to regulate.

    I then thought of transistors, but I'm not to familiar with them in being used as a switch, and from what I read, it probably won't work.

    I would really love to get this working in a simple plug and play method. I don't have time to write some code and create an piece of hardware paired with software to monitor the second input's voltage.

    Simply put, if the second input's voltage goes higher then 0, then open the first input and close the second one until the second one's voltage goes <= 0 and then close input one and stay like that until the condition is met again.

    Thanks all!
     
  2. Arouse1973

    Arouse1973 Adam

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    Dec 18, 2013
    When you say higher than zero, do you have a particular lower level in mind or is this line level voltages?
    Adam
     
  3. SethB

    SethB

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    Oct 12, 2015
    It would be line level voltages. As anything higher than zero would signify that there is sound being played. The amount of voltage coming out of a 3.5mm headphone jack is extremely low and barely measurable on a volt meter. I wonder, could we measure resistance without some sort of software end? I am beginning to think what I want is impossible without the use of software.
     
  4. Arouse1973

    Arouse1973 Adam

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    Dec 18, 2013
    The level could be as high as 2 Volts, depending on the volume adjustment. You don't need software to do this.
    Adam
     
    Martaine2005 likes this.
  5. Martaine2005

    Martaine2005

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    May 12, 2015
    It certainly doesn't need software and is very much still used in audio mixers for Dj's and the mic.
    Are you talking about a lazy mans mixer?
    When the 2nd channel plays the first auto mutes? And vice versa?
     
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  6. Martaine2005

    Martaine2005

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    May 12, 2015
    Same timing Adam. You beat me by 0.000000025μs:p

    Martin
     
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  7. Martaine2005

    Martaine2005

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    May 12, 2015
    However, the above mentioned mute is not the answer and sounds awful just cutting/muting.
    Better to have the 2nd channel fade to mute and vice versa.
    I don't know how to do it though:p

    Martin
     
  8. SethB

    SethB

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    Oct 12, 2015
    I guess. Yes, except, channel one is always live, and only mutes when channel 2 begins to play. So channel two is the "switch" which dictates if channel one should mute or not. Channel one playing should not mute channel two as it will be the "primary" audio source.

    I never heard of a "lazy mans mixer" and google searches are worthless xD as I get a mug that mixes by pressing a button.......

    I really don't care for "fade to mute" and then vice versa. The application it will be used in is in my car. I have music (coming from my cell phone) in channel one that I want always to play, then channel 2 begins to play (my Garmin GPS) to tell me what it must. I only have one input on my radio and want my music to mute so I can fully hear the GPS.

    I guess the volts could be as high as 2 volts, but definitely not in my application lol.
     
  9. AnalogKid

    AnalogKid

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    Jun 10, 2015
    Not difficult, don't need any software. Assuming a single +12 V power source. This can be done with a $3 Chinese "audio detector" module and a little modifying, or you can build one from scratch. One possible circuit is that the Garmin audio goes into a comparator such as an LM393, and that drives a low-power SPDT relay that switches between the two audio sources. No matter how you slice it, there will be a slight delay between the true start of Garmin audio and when it starts coming out of the amp, and a slight delay between when the Garmin audio stops and when the system switches back to music. The shorter these delays are, the more likely that there will be false trips.

    ak
     
  10. SethB

    SethB

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    Oct 12, 2015
    I figured there would be delay. Like 200 ms at most probably. Your method should work, but I was looking along the lines of a plug and play kind of thing without the need for external power. Only reason for that is I'm lazy and have enough wires tapped behind my radio for my bluetooth and such. xD

    I will look into this and see how much time I will need to spend to fully install it. I may just go the route of a stereo mixer and have my music a slight bit lower then the Garmin so when the Garmin comes on it will be extremely loud in comparison to the music.

    Thank you AnalogKid. And everyone else.

    Btw, first time member here and I really like the layout and design of the site. Good job.
     
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