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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
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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