impedance of the speaker you are using,
attach this same wire to the 4 or B ohm
OUTPUT terminal of either channel. Con-
nect the other wire from the "common" of
the speaker to the "common" of the same
channel OUTPUT (C). t6 ohm speakers
are attached to the 8 ohm tapping. You
should now connect a ]oad resistor across
the amplifier output terminals o{ the chan-
nel that you are not using to "load" this
channel. Choose a 10 watt resistor of the
same ohm rating as the speaker you are
using and connect it to the free channel,
duplicating the speaker connections. How-
ever, if you wish, you may attach an ex-
tension speaker for use in another room
instead of a resistor. It is very important
throughout your speaker wiring that you
make absolutely certain that no loose
strands of wire are shorting out (touching)
adjacent terminals.
Stereo: Use the same code designation to
make identical connections for the two
channels. Proceed exactly as ahove. First
wire the channel A speaker system to
channel A OUTPUT; then similarly wire
the channel B speaker system to channel
B OUTPUT (See illustration). Nothing
more need be done.
Phasing: If one or both of your speakers
have no identification markings you will
have to phase the speakers correctly in the
following manner. Connect the speakers to
the correct impedance output terminal of
each channel. Choose a good monophonic
record containing sustained, deep bass
passages. While you listen to these pas-
sages, reverse the two connections of one
channel only. In one of the two positions
the bass will be out of phase-the speakers
will counteract each other and bass re-
sponse will lose both quality and volume,
In the other position the speakers combine
their bass energy and reproduction sounds
better and fuller. This efiect is most ap-
parent if the bass control is at maximum
(both channels) and the speakers are
placed about two feet apart, facing each
other. Fasten the wires down in the cor-
rectly phased position.
Center Channel Stereo: First connect the
two main channels as outlined above. Cor-
rect phasing if speaker terminals are un-
marked. Then connect the center channel
speaker, one lead to the 4 ohm terminal of
channel A and the other to the 4 ohm ter-
minal of channel B. Reverse terminals to
determine the best phasing position.
In many cases it is desirable to reduce the
volume of the center channel speaker. The
best way to do so is to use a "T" ot "L"
pad, easily mounted at the rear of the
speaker baffie. Ask for a connection dia-
gram when you obtain either one at your
local high fidelity or radio parts dealer.
If you use this A plus B'signal speaker for
monophonic reproduction in another room,
you do not have to check for phasing.
hunt,
Hum happens in the best of circles, par-
ticularly in ground loops. Every program
source should be grounded to the ampli
fier. And all of them in turn should be
grounded. Disconnect all sources and out-
puts from the amplifier except the speakers.
If there is hum, reverse the AC plug. Then
re-connect one program source at a time to
locate which, if any, induces hum. If one
does, and it is well grounded, move its con-
necting cables, even the whole piece of
equipment to various positions. You may be
troubled with hum induced by a strong AC
field. Phono pickups are especially sus-
ceptible to this type of field and should be
well shielded from the transformers or
motor of other audio equipment. If phono
hum persists, check installation instruc-
tions provided by the cartridge manufac-
turer. There are some general rules here
that you may wish to follow. The ground
side of the shielded cables {rom the car-
tridge should not make contact with the
turntable chassis, nor should the two shields
make contact except at the amplifier. Use
insulated shielded cables. The tone arm
should be grounded to the turntable chas-
sis and the latter to the motor. Tone arm
grounding, which is often efiected only
through the bearings, can cause hum. If
all other attempts to cure phono hum have
failed, try to achieve better grounding by
the use of fine braided wire.
