Limiter Switch; Short Circuit Protection; Thermal Protection; Bridge Mode - YORKVILLE AP800 Owner's Manual

Modes
The AP800 can be configured for
dual-MONO, STEREO, or BRIDGED
MONO operation via this rear panel
MODE switch. The following is a
description of each mode:
Mono Mode
• Channel A and B inputs are
paralleled
• Each gain control adjusts the signal level for its
respective channel
• Output signals are of equal phase.
• Two loads are driven.
• Loads are connected between the BLACK and RED post
on each channel.
Stereo Mode
• Channel A and B inputs are seperate.
• Two independent amplifiers, Amp A and Amp B.
• Two loads are driven.
• Loads are connected between the BLACK and RED posts
on each channel.

Bridge Mode

• Channel A and B inputs are paralleled. GAIN-B has no effect.
• Output signals are equal in amplitude but opposite in phase.
• One load is driven.
• The load is connected between the two RED binding
posts. The BLACK posts are not used.
Subsonic Filter Switch
The AP800 features a specially designed
subsonic filter which effectively blocks
potentially destructive energy in the
band below 40-Hz. The filter provides
an 12 dB/Oct. skirt below 40-Hz. It is
implemented with a two pole network
designed to minimize phase shift down to
40 Hz. We recommend using this filter in
conjunction with some subwoofers and
with all high power full range cabinets.
With the filter disabled, the AP800 is flat
down to 6-Hz, and rolls off at 12dB/Oct below that.

Limiter Switch

With the internal limiters activated, the
AP800's gain is continuously adjusted
to fit the signal within the available
dynamic range. Occasional clipping
is permitted. The limiters will not only
help to protect your system's horns and
tweeters, but will automatically make
the best use of the available dynamic
headroom. With the limiters activated,
all you need to do is turn up the signal
level until you start to see some clip-
ping. The limiters will make sure that you are getting the maxi-
mum clean power output at all times. Setting the switch to the
OUT position completely disables both limiters.
CAUTION: The AP800 can deliver over 800 Watts of power into a bridged load. Yorkville's own high power speaker systems have cir-
cuit-breaker protection built in. Although these speakers will protect themselves, they are unlikely to be damaged by a bridged AP800.
However, many other speaker manufacturers make "high power cabinets" with no protection features at all.
Yorkville Sound is not responsible for any damage which may result as a consequence of exceeding such a speaker's power handling capa-
bility. Yorkville's two year unconditional warranty does not cover any consequential damages to non-Yorkville equipment. Please consider
these facts carefully before you choose to run your AP800 in bridged mode!
2
Protect LED
In the event of a shorted load, or a load which is of too low
an impedance for the amplifier to handle ,the PROTECT LED
will flash alternately in about 7 second intervals. The sound
may come on and off at ½ second. In this case, the fault is in
the speakers or the speaker cables and should be located and
remedied. No reset of the AP800 is required to restore proper
operation. The protect LED will stay on if the amplifier has
overheated. Check the speaker load impedance, the position
of the load select switch, and any restrictions to air flow at the
air intake or exhaust vents of the amplifier.

Short Circuit Protection

The AP800 is fully protected against all possible passive
load conditions. It can operate with a dead short continu-
ously without damage. (However, we don't recommend
that you short your AP800 "just for fun." Shorts do create a
lot of stress on the output devices). The output stage uses a
unique triple slope VL limiting scheme which is sophisticated
enough to remain inert during transient currents in excess of
40 Amperes and phase angles of more than 45 degrees, yet
is capable of protecting the output stage from damage due to
accidental short circuits and improper loads.
DC Protection
In the unlikely event of the AP800's outputs "going DC," a
thyristor circuit will short the output terminals and divert all
potentially harmful currents away from your speakers.

Thermal Protection

In the unlikely event that the AP800 overheats, the signal will
be sporadically cut off and the PROTECT LED will stay on. If
further heating occurs, (due to some malfunction), an inter-
nal thermal breaker will interrupt the primary circuit. There
is no visible indication of this rare condition. The AP800 is
designed and tested to operate under "worst case" conditions
without shutting down, so if you experience a thermal shut-
down you should check for blocked air flow.
Cooling
The fan draws air in from the front and expels hot air through
the rear vents. This is compatible with our other amplifiers
and with most installations. Since hot air rises, the heated air
forcibly expelled from the back tends to rise away from the
equipment rack. This draws cool air from the floor upwards
into the front of the rack. In some cases where the rear of the
rack is obstructed it may be necessary to install rack fans to
aid cooling. If there are no obstructions, no secondary cooling
is required.
Fan Filter Maintenance
The AP800 is factory equipped with a fan filter mounted
on the air intake grill on the amplifier's front panel. Regular
cleaning of this filter will increase the amplifier's long term
reliability. The filter should be removed and washed at the first
sign of visible clogging. This will typically occur every four to
six weeks depending on use and environment. Replacement
filters are inexpensive and can be ordered through Yorkville
dealers. The foam filter should be removed if a regular inspec-
tion schedule is not going to be followed. The amplifier can
operate without the filter in place, but the amplifier should be