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This is
a simple
microphone
preamplifier
circuit
which
you can
use
between
your
microphone
and
stereo
amplifier.
This
circuit
amplifier
microphone
suitable
for use
with
normal
home
stereo
amplifier
line/CD/aux/tape
inputs.
This mic
preamp
can take
both
dynamic
and
Electret
microphone
inputs
(preamplifier
provides
power
foe
Electret
microphone
elements).
The idea
of this
circuit
is to
keep the
design
as
simple
as
possible
to be
easy to
build.
That was
my goal
when I
needed a
simple
external
microphone
preamplifier
for my
mixer.
The
performance
of the
circuit
is
nothing
superior
but can
be used
with
many not
so
serious
projects.
The
circuit
is a
simple
one
transistor
amplifier
with
amplification
of about
30-40 dB
(depends
on
transistor,
temperature
and
voltage).
The
dynamic
mic
input is
just a
simple
one
transistor
amplifier
circuit
with
nothing
special.
Electret
microphone
input
has a
resistor
R1 fo
feeding
current
through
electret
microphone
capsule
when it
is
connected
to the
electret
microphone
input.
Electret
microphone
needs
some
current
(about 1
mA)
flowing
through
it to
operate,
because
there is
a small
amplifier
circuit
inside
the
microphone
capsule.
This
circuit
is
suitable
for all
typical
cheap
electret
capsules
which
available
from any
electronic
component
shop.
Because
electret
microphones
have
higher
signal
level
output,
it is
quite
easy to
overdrive
the
amplifier
when you
shout to
electret
microphone.
The
circuit
is bet
to build
to a
small
metal
box
where
you have
a small
9V
battery
for
powering
it.
Battery
power
and
metal
box keep
noise
away.
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