Power Amplifier Protection; General Operating Instructions; Ac Power Circuit-Breaker; Rack Mounting - YORKVILLE AP812 Owner's Manual

10

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 ther-
mal 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.
The AP812/818's power amplifier also features speaker protection in case of DC-off-
set. This is a very unlikely occurrence given the amp's inherently stable design, but
should it happen, the output power is instantly shorted to ground and the speakers
are saved. The AC mains breaker on the back panel will blow in response to this con-
dition (among others). If your breaker blows more than once in a short space of time
and the problem does not appear to be AC overload (see below), switch the power off
and take your AP812/818 to a qualified technician.

AC POWER CIRCUIT-BREAKER

Located on the back panel near the SPEAKER connectors, this circuit-breaker's main
function is to shut the AP812/818 down completely in case of an AC power overload.
If, for example, the unit were accidentally connected to a high-voltage power outlet,
this breaker would open as soon as the AP812/818's POWER switch was flipped on. If
this breaker opens more than once in a short space of time, try plugging the AP812/818
into another power outlet. Also, see above regarding DC-offset speaker protection.
RACK MOUNTING (applies to AP-812 only)
To rack-mount the AP812 you will need to purchase a pair of the accessory model
RK812 rack ears, then simply remove the three screws holding each of the AP-812's
two end moldings in place and use the screws to mount the rack ears to the sides of
the mixer.

GENERAL OPERATING INSTRUCTIONS

1. Connect the AC power cord to a 120Volt AC grounded power outlet (220 to 240
Volts in export units).
2. Switch on the POWER and turn the MAIN and MONITOR MASTER controls to
OFF for now.
3. Connect low-impedance microphones to the 3-pin XLR type MIC inputs.