lui@CS.UCLA.EDU (03/30/88)
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?
Stephen Lui
ARPA: lui@cs.ucla.edu
UUCP: ...!{cepu,ihnp4,trwspp,ucbvax}!ucla-cs!luipokey@cpocd2.UUCP (Todd Wayne) (03/31/88)
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
daver@felix.UUCP (Dave Richards) (04/07/88)
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? Radio Shack also sells patch cords that have a built-in resistor to do this for you. There's a different one depending on whether the mic input is low or high impedance. With the right patch cord and adapters you should be able to hook everything up. Dave
sheperd@raider (Charles Cain) (04/12/88)
The device that Stephen Lui is looking for is called an L-pad. It will
allow you to take a line level signal and lower it to a mic level signal
in varying amounts. It operates just like a volume control except it will
not short out the outputs of the line level source or the inputs of your
mixer if the control is turned to the extremes. Also you may try to find
out exactly how much attenuation you need by measuring the output of the
line level device and the midrange input level of your mixer. Typically
line level can be from -15Db to 0 db and mic level from -70Db to -50Db
but sometimes that is not always true. The L-Pad will allow you to set it
to your level and if you should ever have to change the setup around, it
is easier to set it back up with one than with a fixed attenuator. Hope
this helps.
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