Xref: utzoo rec.music.synth:2993 rec.music.makers:1567 rec.audio:5621 sci.electronics:2654
Path: utzoo!mnetor!uunet!husc6!bloom-beacon!tut.cis.ohio-state.edu!mailrus!ames!oliveb!intelca!mipos3!td2cad!cpocd2!pokey
From: pokey@cpocd2.UUCP (Todd Wayne)
Newsgroups: rec.music.synth,rec.music.makers,rec.audio,sci.electronics
Subject: Re: Converting Microphone Level Inputs to Line Level Inputs
Message-ID: <1221@cpocd2.UUCP>
Date: 30 Mar 88 18:06:00 GMT
References: <10742@shemp.CS.UCLA.EDU>
Reply-To: pokey@cpocd2.UUCP (Todd Wayne)
Organization: Intel Corp., ASIC in the Desert, Chandler AZ.
Lines: 34

In article <10742@shemp.CS.UCLA.EDU> lui@CS.UCLA.EDU (Stephen Lui) writes:
>I have a Radio Shack Realistic mixer which has 3 microphone inputs that I
>never use. I want to convert these microphone inputs to line level inputs.
>Does this involve inserting a simple resistor in series? How do I
>calculate the value of the resistor? Do mic inputs perform any type of
>equilization similar to phono cartridge inputs?

I hacked an IBM PC telephone interface card once when I was back in
school.  I converted a mic level input to a line level input by
swithching a transconductance amplifier OUT of the circuit.

After I figured out what the gain of the amplifier circuit was, I
discovered that the next section was set up for line level voltages.

What you want to do depends completely on the circuit and the impedences
involved on either side of the amplifier circuit for a particular input
(I assume that any reasonable mixer would have some kind of amplifier or
at least some form of isolation for each input).  You might require
clipping out the amplifier AND adding some resistors - but I think the
section after the input stage should be high impedance.

I personally think having your addition switchable in/out, such that out
leaves the original circuit, is a very good idea.

>	Stephen Lui
>	UUCP:  ...!{cepu,ihnp4,trwspp,ucbvax}!ucla-cs!lui

Hope this helps,
     Todd
-- 
"Here, this will cheer you up.  The martian moves when you flip the pages!
      Watch, you can see him eat an astronaut!" - Calvin, 1/28/88
	   ATT: (602) 961-2399  DOMAIN:pokey@cpocd2.intel.com
      UUCP:...!{decwrl|hplabs|oliveb}!intelca!mipos3!cpocd2!pokey