[SECC] N1MM Sound Card Interface

[Scott Straw]

Gordon,

Remember that I'm only a sound engineer wanna-be!  I will preface my
comments by reciting my favorite "truth to live by", but in this case it
really applies to me:

"Those of you who think you know everything tend to really irritate the fire
out of those of us who do."

I am afraid that I might come off sounding like I think I know everything,
so those of you who do, don't hesitate to set me straight.

Basically this is a issue that we deal with all of the time in sound
reinforcement and recording.  The keyboard, guitar amp, CD Player, or
DVD/VCR generates an electrical audio signal with the aid of a cable that
sucks energy from "the magic wall." The variable frequency AC current is
usually around 1v.  A dynamic microphone however,  must make its own juice
by moving a spring-loaded magnet back and forth inside a coil - no magic
wall for it.  In spite of its best efforts, the microphone will probably at
best generate a milli-volt or so.

Most audio mixing consoles and microphone recording devices are engineered
to deal with the wimpy efforts of the dynamic microphone, and get really
upset when you ram an entire volt down their input. Likewise, a device
looking for 1v signal will ask the microphone plugged into it, "Where's the
beef?"  Transforming audio signals, which are really just variably
oscillated electrical voltages, is a common practice.  Fortunately there are
only about three standard voltage levels that we  deal with: professional
line level (1v), consumer line level (.7v), and mic level (1mv). And also as
a matter of fortune, close is usually good enough thanks to variable value
resistors (aka volume knobs).

Now that I've insulted your intelligence, for which I beg forgiveness, I
will suggest that the same solution for his fancy new Icom should work on
your trusty and reliable Drake.  You will need to verify what impedance the
Drake likes best, and just, well, impede the voltage from your computer to
match.


Oh to be a simpleton once again! Curse you damned curiosity!

KB4KBS