About
the
C720
Circuit
Like
most
Josephson
microphones,
the
C720
uses
an
all
discrete
class
‐
A
circuit
to
transform
the
high
impedance
of
the
capsule
to
a
suitable
level
for
interface
with
mic
preamps
and
consoles.
A
cascode
FET
stage
directly
drives
a
special
Lundahl
output
transformer,
which
uses
amorphous
metallic
glass
as
the
magnetic
core
material.
The
result
is
a
much
higher
overload
point,
even
when
the
mic
is
driving
long
cables.
It
is
the
same
audio
circuit
and
transformer
found
in
Josephson’s
acclaimed
e22S
microphone.
The
internal
power
supply
of
the
C720
uses
a
new
electrostatic
circuit
that
provides
capsule
polarization
charge
without
the
use
of
oscillators
or
external
power
supplies.
Only
one
channel
of
the
circuit
is
shown.