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From: [e-mail] (marxhausen paul)
Newsgroups: sci.electronics
Subject: Re: Passive Mixer
Date: 29 Apr 1993 12:42:39 GMT
Organization: University of Nebraska--Lincoln	
Lines: 32
Distribution: world
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[e-mail] (Wendy Shaffer) writes:

>I'm trying to build a mixer for a friend of mine to run several things into
>a single boom box.  I have a circuit that uses an op-amp powered by either a
>couple of 9V batteries or using some kind of power supply.  But in a catalog
>I was looking at recently, a "passive mixer" for guitar was advertised taht
>doesn't appear to use any power at all.  Does anyone know what the circuit for
>this would be, because then I could just adapt it for RCA jacks, and save my
>friend and I alot of messing with batteries and plugs.  Thanks.

Well, the fastest, crudest mixer (aside from just physically connecting
all your inputs together directly) is to run each signal through a 
resistor to a common output.  The resistors give some isolation so the
signal sources aren't driving directly into each other. 

Taking a wild, seat-of-the-pants guess, I'd say that if you are mixing
high-impedance sources like some dynamic mikes, electric guitar pickups,
etc., your resistors ought to be maybe 5K - 10K or so.  If you are mixing
line-level stuff or the outputs of a Walkman, or such, I'd go with 1K.

input 1 --/\/\/\/ -------------+--- output
                               |
input 2 --/\/\/\/\-------------+
                               |
input 3 --/\/\/\/\-------------+


--
paul marxhausen .... ....... ............. ............ ............ .......... 
 .. . .  . . . university of nebraska - lincoln .  . . .. . .  .. . . . . . . .
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