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Sony TA-E88 - Phono and Head Amplifier Circuits

Sony TA-E88
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‘TA-E88/E88B
1-2,
CIRCUIT
DISCRIPTION
4-2-1.
Phono
1
and
Phono
2
Input
Circuits
The
TA-E88/E88B
is
equipped
with
two
phono
inputs
—
PHONO
|
and
PHONO
2.
PHONO
1
@
When
using
high
impedance
cartridges
(output
about
2.5mV):
When
the
FUNCTION
switch
(SI)
is
set
to
the
PHONO
1
position,
the
input
impedance
Zinl
(150kQ,
100pF)
of
equalizer
amplifier
is
con-
nected
in
parallel
with
R1
(75kQ)
across
the
PHONO
1
input
terminal.
They
serve
as
load
impedance
for
the
cartridge
used.
(R
=
50kQ,
C
=
100pF)
®
When
using
low
impedance
MC
cartridges
(output
about
125uV):
The
head
amplifier
is
connected
by
switching
S1.
At
the
same
time,
either
a
3Q
or
40Q
load
im-
pedance
(depending
on
cartridge
impedance)
is
also
connected
to
the
PHONO
1
input
terminal.
For
the
load
of
400
cartridge,
the
input
im-
pedance
Zin2
(100Q)
of
head
amplifier
is
employ-
ed,
and
for
the
load
of
322
cartridge
R2
(332)
is
connected
in
parallel
with
Zinl,
resulting
in
a
25Q
input
resistance.
PHONO
Tf
PHONO
7
ZINI
Ri
HEAD
AMP
ls
150kQ.
100pF
—FUNCTION—
PHONO
1
R2
&}
402—
7
HEAD
AMP
32
Fig,
1
PHONO
2
@
The
PHONO
2
input
is
basically
the
same
as
the
PHONO
1
input,
but
also
is
equipped
with
a
PHONO
2
PHONO
2
T
°
a
ae
|
rey.
OTL
a)
bf
6
2
r
|
~LOAD
R-
-LOAD
C—
10k
—100kQ.
100p—S00pF
(varied
in
10k9.
steps}
(varied
in
10OpF
steps)
Fig.
2
cartridge
load
selector.
It
is
adjustable
over
10k
to
100kQ
and
100pF
to
SO0pF
ranges
when
using
high
impedance
cartridge.
®
This
switch
(S801)
located
on
the
top
case
is
a
kind
of
rotary
switch.
Fig.
3
1-2-2.
Head
Amplifier
Generally,
the
very
low
level
signals
produced
by
an
MC
(moving
coil)
cartridge
are
amplified
by
step-
up
transformer.
On
the
other
hand,
in
the
TA-E88/TA-ES88B,
this
amplification
is
performed
by
a
built-in
head
ampli-
fier.
Although
the
use
of
active
amplification
ele-
ments
(rather
than
passive
transformers)
causes
some
deterioration
of
S/N
ratio,
these
problems
have
been
successfully
overcome
in
the
TA-E88/E88B
by
employing
parallel-connected
transistors
in
the
head
amplifier.
The
head
amplifier
includes
a
main
amplifier
stage
consisting
of
eight
transistors
(Q101
to
Q108)
con-
nected
in
parallel,
and
another
eight
transistors
(Q109
to
Q116)
differentially-connected
to
this
main
stage,
achieving
gain
of
27dB
with
usually-
low
noise.
buffer
amp
ey
output
input
4
_
—_
--3}-4
™
101-108
sits
i
Fig.
4
@
Parallel
Connection
When
a
transistor
is
used
for
amplification
pug-
poses,
the
current
flowing
between
the
collector
and
emitter
of
the
active
transistor
is
placed
under
control.
Signals
from
the
base
terminal
pass
through
the
internal
resistance
of
the
base
spread

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