Eico ST 40 - Balance, Level, and Loudness Controls

Ifci&iSteJ
ST«Q
PAGE
8
BALANCE
Control:
Used to.
achieve
equal
left
and
right
side
program
levels
In stereo.
Effective
in
mono
to
center
the
apparent
source
between
the
speakers.
Neither
channel
amplifier
Is favored (as
to
gain)at
the
zero
setting
(mid-rotation).
As
the control
is
turned
clockwise
from
zero, the
channel
2 Is
(right)
speaker
Is
made
louder and
the
channel
1
(left)
speaker
Is made
softer,
whilethe
overall
level remains
about
the
same.
As
the
control
is
turned
counter-clockwise
from
zero,
the
channel
1
(left)
speaker
Is made
louder
and
the
channel
2
(right)
speaker
Is
made
softer,
while
the
overall
level
remains
about
the same.
BALANCE
v'
(CHECK)
Slide
Switch:
If
you
have iden-
tical
left and
right speakers
(or
dissimilar
speakers
of
nearly
equal
efficiency),
the
BALANCE
control
can
be set
properly
by means
of
the
BALANCE
v/
(CHECK)
slide
switch as
follows:
1. Set
BALANCE
(CHECK) slide
switch to
ON
2. Set
MODE
switch
to
MONO 1
3. Adjust
BALANCE
control
for
minimum
sound
(null)
from
the left
(CH.
1)
speaker.
There
will be
no
sound from
the
right
(CH.
2)
speak-
er.
If the
BALANCE
control
Is turned
either
direction
from
the
proper
setting
(null),
the
sound
level from
the
left speaker
will increase.
4. Return
the
MODE
switch
to STEREO
or
RE-
VERSE
if
the source
is stereo.
NOTE:
In the "null"
method
of
balancing
just described,
this
is
what isbeing
done.
An
identical
signal
is fed to
the
channel
I and
2 amplifiers at
the high
level
input
points
(setting
MODE
switch
toMONO
1).
A
dummy
load
is
internally
substituted
forthe
channel
2
(right)
speaker and
the
channel
2
output
signal
Is
fed back
through a
precision
dividing
network
to the input of
the channel
1
power
amplifier (setting
BALANCE
n/
switch
to ON).
The channel
2
output signal
is
out-
of-phase
with
the
input signal
to channel
1
and
tends
to
cancel
or nullify
it. When
the
BALANCE
control
is set so that
the
portion of the
channel
2 output signal
fed
to
the
channel
1
power
amplifier
input is equal to
the channel
1 signal at
this
point, almost
complete
cancellation
(null)
occurs and
the output
from the
channel
1
speaker
is
at
a
minimum.
This
method
of
balancing
jchieves
equality of gain
in
the channel
)
and
2 amplifiers from
the
high level
in-
puts to
the speaker
outputs.
The
preamplifiers,
which
are ahead
of
the
high
level
input, are
audibly
nearly
equal
In
gain
because
of feedback.
If,
upon
returning
the
MODE
switch
to
STEREO
or REVERSE after
setting
the
BALANCE
control
by this method,
audible balance
is not achieved,
the
indication
is
that the
sources feed-
ing
the amplifier
are
not equal. If the sources
have
their
own level
controls,
such
as
FM or AM
tuners or
Multiplex
adaptors,
then
these
level controls should
be set to
equal
output by
successively
setting
the MODE
switch
ats/CH.l
andv/CH.
2 while adjusting
the
source
level
controls for
equal
output
from each
speaker.
Once
the source
levels
have
been adjusted,
the
null
balancing
method
described
previously
will work ef-
fectively*
If
one
speaker
Is a little
more efficient
than the
other,
you
may
pad
down
the more efficient
speaker
by a series
resistor
up to half
the rated speaker
impedance
(more
will unduly
deteriorate
speaker
damping).
In order
to
make
the
convenient
null
balancing
method effective.
If the speakers
are
grossly
different
in efficiency,
you
will have to
adjust
the
BALANCE
control by succes-
sively
setting
the
MODE switch at
vXCH.l and
s/CH.2,
while finding
the BALANCE
control
setting that
pro-
duces
about
equal output
from each
speaker.
If a stereo
phono
cartridge
has a
marked difference
in
output
between
the two
sides,
you
will
have
to adjust
the
BALANCE
control setting
until
audible
balance
is
achieved,
while
successivelysetting
the
MODE
switch
to\ACH. 1
and\ACH, 1
and
v^CH.
2,
when this input
Is selected.
LEVEL
control:
Used
to
adjust
the listening
level
in
both
channels.
The BALANCE
control
is adjusted after
setting
the LEVEL
control.
Substantial
changes
in
LEVEL
control setting
may
require re-setting
the BAL-
ANCE
control. Adjust
the
output
level controls
in
tuners,
multiplex
adaptor, and tape
machines
with pre-
amplifiers,
to match
the sound
level obtained
on phono,
if possible.
If any
of the
high level
sources can not
provide
high enough
output to
match phono,
simply
set
this
source
to
maximum
output.
LOUDNESS
slide
switch: A
characteristic of
human
hearing
is
thatsensitivity
to bass tones
diminishes more
rapidly,
a's the listening
level
Is
lowered,
than sensi-
tivity
to middle and
high frequency
tones. Many people
find
the audible
loss
of bass
at
low listening levels
un-
satisfying*
Setting
the
LOUDNESS slide
switch to
ON
provides
a
compensating
amount of
bass
boost at low
listening
levels. Do
not leave
the
LOUDNESS
switch
at
ON when
listening at normal
volume, since the
amount of bass
boost
provided
will
usually be
excess-