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1. Description
The PRO series speaker selectors are highly efficient dual-source, impedance-matching selectors. These high-quality speaker selectors
are designed for use with either 4 Ohm or 8 Ohm amplifiers and 4 Ohm to 8 Ohm speakers.
The PRO speaker selectors are equipped with a low-frequency protection circuit to reduce subsonic signals. This allows high power
operation without amplifier shutdown. TIle PRO units employ audiophile-grade impedance matching autoformers to maintain a safe
operating load at the amplifier while distributing maximum power through the system. Autoformers are very efficient because of the
small loss incurred as a result of heat dissipation. TIle series is equipped with a back panel rotary switch, which is used to set the appro-
priate impedance based on the number of pairs of speakers connected. This switch selects the proper taps of the autoformers, allowing
all of the amplifier's power to be delivered to the speakers.
TIle PRO speaker selectors can be connected to one or two amplifiers. A front panel button allows switching between the two ampli-
iiers for all speakers connected to the unit.
2. Connections
The PRO series have removable modular snap connectors thaI provide cUlor-cuded wire terminations without the need for set-screws.
Strip about 3/8" (0.95 cm) of insulation from the ends of all wires to be connected. If necessary, twist the exposed conductor to insure
that no loose strands exist. Remove the AMP A connector by firmly pulling it out of its 4-pole connector. Lift the wire locking lever on
connector. Insert the wires from amplifier A output, being careful to observe the polarity, then lower the lever with a "snap." In the same
way, connect the amplifier B output to the AMP B connector. Follow the same procedure to connect each pair of speakers to the appro-
priate SPEAKER connector, observing proper channel and polarity. If external volume controls are used, connect speaker wire from the
appropriate speaker connector on the PRO to the volume control input. Speaker connections can support multiple speaker pairs wired
in parallel or series, provided their combined impedance is a minimum of 4 ohms.
3. Operation
To ensure safe operation of the amplifier, an impedance level must first be selected using the rotary switch labeled SPEAKER PAIRS
located on the rear of the unit. This switch should be set to the total number of speaker pairs being connected to the unit. Set the svvitch
based on the following conrlitions:
•
If the amplifier and the speakers Jre both 4 ohms, set the rotary switch to the number of pairs of speakers connected to the PRO.
•
If the amplifier and the speakers are both 8 ohms, set the rotary switch to the number of pairs of speakers connected to the PRO.
•
If the aillplilll'j
,c, ,j
~;i,;:!,
1;,;
::li'
"!lz',lkf':S drC'·: ohms, set the rotary switch to TWICE the number of pairs of speakers connected to
the PRO.
•
If the amplifiel' is 4 ohms ,lnd
till'
51)(\11,:('1'5
drc' () ohms, set the lutary switch to HALF the number of pairs of speakers connected to
the' PRO
After selling the proper impedance level, the spedkers Cdn be turned on and off in any combination.
To switch between the A <md B alllrlifiers, push the AMP A / AMP B hutton located on the front panel.
4. Setting System Volume
It is impol1dllt tu prupl.'riy adjust an impedance-matching system to avoirl distortion or DC clipping (DC voltage will be produced from
an amplifier that is overworked or that h,15 ,ln improper load). These can cause an amplifier/receiver to go into protection, and can
cause autoformers on volume controls to hmt up, damaging system components. To set up the system, the amplifier/receiver volume
should be at its lowest setting, and the in-wall/selector volume control should be at the highest setting. Slowly adjust the
'lmplifier/re'ceivpr volume' tu
,1
h'(·1
thZlt is acceptable for the amplifier to produce without clipping.
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