9
Power Amplifier - General
The
AP812/818
has a
built-in
800 watt
stereo
power amplifier. Each channel has an
input sensitivity of
+4 dBv (1.4 volts RMS) for full-power output and each can deliver
over
400 watts into a 4 ohm speaker load. These amplifiers incorporate computer
designed internal heatsinks and a
variable-speed
fan which automatically provides
quiet operation 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 maxi-
mum 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
Two
1/4-inch jacks and one
Speakon®
connector 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 applications we
recommend
14-gauge cables equipped with the
Speakon®
connectors. This will reduce
risk of resistance buildup. The
Speakon®
system, developed in recent years by
Neutrik
in Switzerland, features block-style contacts capable of handling large amounts of
power and the connectors lock down to prevent accidental kick-outs.
Connect one or two
8 ohm
speakers or one (only)
4 ohm speaker to each chan-
nel. When connecting the
Speakon’s®
, push them in firmly and twist in a clockwise
motion. Push the tab and twist counter-clockwise to disconnect.
User tip: To connect two (8 ohm) speakers to one or both of the AP812’s powered
output channels via the
Speakon® connectors, run a single Speakon® -equipped
cable, e.g.
Yorkville model SP2-25SS or SP2-50SS with Speakons® at both ends
(most higher-powered speaker enclosures now feature
Speakons® as well) from the
AP812/818 to one of the enclosures. Now run a second cable from one cabinet to the
next via their dual, parallel inputs.
Power Amplifier Protection
The
AP812/818’s
power amplifier is protected from damage due
to open, shorted or
excessively low speaker loads
. It will continue to run into a low (less than
4 ohms)
overall speaker impedance or even a total short-circuit for a brief time, however the
amplifier’s defense system will be activated. First, the
built-in limiter
will reduce output
power levels and the fan speed may increase. Then, if the condition worsens, a thermal
protection circuit will shut the power amplifier down. When this happens, check your
system for restricted air intake/exhaust at the
AP812/818
. Also check for shorted cables
or connectors and/or reduce the number of speakers being driven. In a few minutes
when it has had a chance to cool down, power amp function will resume.
User tip:
a) If the power amplifier shuts down as above, the mixer section will continue to
function. This means that, if the
AP812/818’s power amp fails to come back on
(unlikely) and you have a spare power amplifier available, you can connect it to
the
AP812/818 via the LINE OUTPUT jacks. See under PRE and POST EQ LINE
OUTPUTS for further information regarding connections.
b) Because the amplifier is also protected against open-circuit conditions, you
may use the
AP812/818 without any speakers connected, for example if you
wanted to do some recording.
Содержание AP812
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