Radio Shack MPA-125 用户手册

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 

 terminal on the back

of the amplifier.

5. Connect the speaker’s positive (+) ter-

minals to the speaker terminal (

Ω

Ω

Ω

Ω

, 

Ω

Ω

Ω

Ω

,

or 

Ω

Ω

Ω

Ω

) on the back of the amplifier that

matches the total speaker impedance as
calculated in Step 3.

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.

• 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 

 and 

 terminals on the back of

the amplifier.

32-2003.fm  Page 11  Tuesday, March 28, 2000  10:45 AM