Radio Shack MPA-125 Stereo Amplifier User Manual


 
11
Connections
3. Connect the two pairs of speakers in
parallel. If you connected 8 ohm speak-
ers the total impedance of both pairs is 8
ohms (16
÷
2 = 8).
Note:
If each of the four speakers is 8
ohms, the total speaker impedance of
the combined series/parallel connection
described above is also 8 ohms. Like-
wise, the total speaker impedance is 4
or 16 ohms if the speakers are 4 or 16
ohms, respectively.
4. Connect the speakers’ negative (–) ter-
minals to the
COM
terminal on the back
of the amplifier.
5. Connect the speaker’s positive (+) ter-
minals to the speaker terminal (
4
,
8
,
or
16
) on the back of the amplifier that
matches the total speaker impedance as
calculated in Step 3.
Connecting Speakers with Trans-
formers
For the best results when you connect two or
more speakers to your system, use a line
transformer (not supplied) for each speaker.
Transformers offer these advantages:
You can connect speakers with different
impedances without causing differ-
ences in output between the speakers.
You can add or remove a speaker from
the system without having to recalculate
the entire system’s impedance.
You can reduce signal loss when you
use speaker wire over 50 feet long.
Line transformers have several connectors
called taps.
The primary taps (on one side of the trans-
former) are the inputs and are rated in watts.
The secondary taps (on the opposite side of
the transformer) are the outputs and are rat-
ed in ohms.
Cautions:
Before you connect the speakers, be
sure the total wattage of the primary tap
you intend to use does not exceed the
amplifier’s maximum 100-watt output
power rating.
Avoid multiple connections to the
70V
RMS
and
COM
terminals on the back of
the amplifier.
Taps
Primary
Taps
Secondary
Taps
32-2003.fm Page 11 Tuesday, March 28, 2000 10:45 AM