Specifications

CONNECTING A CENTER LOUDSPEAKER
Ventilation
,
When using the SCA-35 it is essential that it have ade-
quate ventilation. This unit dissipates 110 watts of heat,
and you can see that there is the same heating effect as
with a 110 watt incandescent lamp in a small metal con-
tainer-the case will get quite watm to the touch, and
should have air space above to permit the heat to dispell.
There should always be several inches of air space above the
unit and behind it. Never place anything directly on top
of
the cover when the amplifier is operating.
Under some conditions it is advantageous to be able to
use a
center loudspeaker which handles the monophonic
signal
(sum of left and right channels) derived from the
two parts of the stereophonic signal. This center speaker
can eliminate the "hol.e-in-the-middle" effect of speakers
which are widely separated. The composite center signal
can also be used with a remote loudspeaker for monophonic
reproduction
in another area. The signal for the center.
speaker is available on the back panel of the SCA-35 with-
out need for another amplifier.
5
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Switch the stereo-mono switch to "mono." Then adjust
the balance so that the sound is equal from both loud-
speakers.
Stand slightly forward of the speakers at an
equal distance from each. Move from side to side while
trying to loeate the sound source. If the speakers are phased
correctly, the source will be in the center, when you are in
the center, and will shift smoothly to whichever speaker
you approach. If the speakers are phased incorrectly, there
will
be an abrupt jump in the location of the sound, and it
will shift suddenly from one side to the other with little
or no apparent centering.
To correct the phasing of the loudspeakers, if it is incor-
rect, you must interchange the two wires between the
SCA-35
and one of the speakers. This can be done either at
the amplifier or at the speaker.
Cabinet Mounting
The oversize front panel on the SCA-35 facilitates cab-
inet installations. The rubber feet are not used.
A
supporting shelf installed flush with the bottom of a
3
1
:;{o" by 13Yt
o
"
cutout in the cabinet panel is required.
A
3Y2" square ventilation cutout should be made in the
shelf to coincide with
the punched-out section of the SCA
bottom plate, under the output tubes. A PBK bracket kit,
which eliminates
the need for the shelf, is available directly
from
Dynaco for $2.00. No C.O.D.'s please.
Adequate ventilation is imperative. The warranty does
not cover equipment which has been subject to abuse as the
result of insufficient ventilation. Cabinet installations fre-
quently require the use of a small circulating fan, particu-
larly where the SCA must be mounted close to a tuner, or
where vertical (face up) mounting is necessary. Under no
circumstances should the SCA be stacked immediately
above
or below the Dynatuner.
USING YOUR SCA-35
Other Back Panel Connections
There are two AC outlets on the back panel to which the
wer cords of
auxiliary equipment may be connected. One
these outlets is switched in unison with the SCA-3S when
e
SCA's power switch is operated. The other outlet is not
switched and will furnish power at all times that the SCA's
power cord is plugged in. The switched outlet may be used
to power a radio tuner so that this can be turned on and off
with
the SCA-3S. The lUlswitched outlet should be used for
a
turntable, record changer, or tape machine. These devices
require mechanical switching
and should not be switched
automatically when the SCA-35 is turned on or off.
The line cord of the SCA-35 should be plugged into a
suitable outlet furnishing nominally 120 volts, 60 cps alter-
nating current (120 or 240 volts, 50 or 60 cycles for export
models) .
There are two knurled shafts on the back panel which are
used for hum adjustment of the two channels. Their func-
tion is explained below.
Phasing Loudspeakers
For best stereo effect, the loudspeakers should be prop-
erly phased-an adjustment which is made once and can
then be left fixed. Phasing consists of arranging the polarity
{ the speaker connections so that both speakers function
In unison, moving in the same direction at the same time,
on monophonic signals.
Hum Adjustments
Turn the volume down low, set the selector switch on
"phono," and turn on the SCA power switch. After the first
5 seconds,
advance the volume control slowly until you
v ear some hum from the loudspeakers. Then turn the bal-
ance control to cutoff the right loudspeaker, and adjust the
left hum control (on the back panel) for minimum hum.
Repeat this with the balance control set to cut off the left
loudspeaker,
adjusting the right channel hum control.
These controls should give some minimum point {or hum;
and this point should be low enough to be inaudible at
normal listening levels.
Turn the volume down, place a record on the turntable,
and advance the volume until you have a suitable level;
then you can adjust balance and tone controls to your
satisfaction.
The same setup procedure can be followed with a tape
deck, using the tape head input. The minimum hum point
will be at about the same point as with phono. If neither
phono or tape head inputs are to be used, the hum level
will be
much lower, and it may be difficult to determine
where the minimum settings of the hum controls fall. In
this case, since hum should be inaudible, it is not important
whether the controls are set accurately.
Once the associated equipment is connected to the
SCA-35 and you are familiar with the operation of the con-
trols,
you are ready to try it out.
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