Path: cantaloupe.srv.cs.cmu.edu!magnesium.club.cc.cmu.edu!news.sei.cmu.edu!fs7.ece.cmu.edu!europa.eng.gtefsd.com!howland.reston.ans.net!zaphod.mps.ohio-state.edu!moe.ksu.ksu.edu!crcnis1.unl.edu!mpaul From: mpaul@unl.edu (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 Message-ID: <1roifvINNd9n@crcnis1.unl.edu> References: <1rmk8t$8l0@cat.cis.Brown.EDU> <1rmsbuINN59f@MINERVA.CIS.YALE.EDU> NNTP-Posting-Host: unlinfo.unl.edu shaffer-wendy@yale.edu (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 . . . .. . . .. . . . . . . . . . . . . . . . . . . . . . grace . . . . . . . . . . . . happens .