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3. Now connect one 8 ohm subwoofer to the AMP 1 SPEAKER OUTPUT jack and one
8 ohm full-range cabinet to the AMP2 SPEAKER OUTPUT jack.
4. The complete system
is now functional, not
including monitors.
How-ever, if you need
to vary the compara-
tive volume levels of the
subwoofer/s relative to
the full-range cabinets,
another setup will be
required with an exter-
nal power amp for the
subwoofers or employing
powered subwoofers.
In that system, AMP 1 would be for full-range speakers and AMP 2 would be for
monitors. In other words, this is a standard setup but with the MAIN (L) LINE
OUTPUT going to the input of the processor/crossover and then to an external
amp driving the subwoofer/s, or simply direct to the input of a powered subwoof-
er (ours have crossovers built in).
Power Amplifier - General
The AP312 has a built-in 320 watt stereo power amplifier. Each channel has an input
sensitivity of +4dBv (1.4 volts RMS) for full-power output and each can deliver over
160 watts into a 8 ohm speaker load. These amplifiers incorporate computer designed
internal heatsinks and a variable-speed fan which automatically provides quiet opera-
tion consistent with cooling requirements. Cool air is drawn into the front of the
mixer, and heated air is expelled along the bottom of the back. Even at maximum
power, this arrangement results in quiet, dependable performance.
PLEASE NOTE: THE AIR VENTS AT THE FRONT AND BOTTOM REAR OF THE
MIXER ARE ESSENTIAL FOR PROPER OPERATION. BLOCKING THE FREE FLOW
OF AIR THROUGH THE MIXER WILL RESULT IN SYSTEM SHUT-DOWN DUE TO
OVERHEATING. REPEATED OVERHEATING MAY EVENTUALLY CAUSE DAMAGE.
PLEASE KEEP THE VENTS FREE OF OBSTRUCTIONS.
Speaker Connections
The two 1/4-inch jacks are in parallel with each amp-channel output stage. This allows
the use of speaker cables equipped with either type of connector. For full-power applica-
tions we recommend 18-gauge cables or heavier - possibly 16-guage, or even 12-guage
Connect one or two 8 ohm speakers to each channel.
Note: The amplifier puts out maximum power into 8 ohms per channe
Power Amplifier Protection
The AP312’s power amplifier is protected from damage due to open, shorted or exces-
sively low speaker loads. It will continue to run into a low (less than 4 ohms) overall
speaker impedance, or even a total short circuit, however the output power will be
automatically reduced to maintain an optimum safe operating temperature. In a worst-
case situation, the thermal breaker on the transformers primary windings will shut the
AP312 down until it cools sufficiently.
User tip: Cooling will require a few minutes. Take this time to check the number,
and impedances of connected speakers (are there significantly more than two 8 Ohm
speakers per channel?). Also check inside the speaker cable jacks; there may be stray
bits of wire that could be causing short circuits. Also, connection tabs may be too
close to each other. Remove the short and/or reduce the number of connected speak-
ers.
AC Power Circuit-Breaker
Located on the back panel near the SPEAKER connectors, this circuit breaker’s main
function is to shut the AP312 down completely in case of an AC power overload. If,
for example, the unit were accidentally connected to a high-voltage power outlet, this