Thermal Protection; Limiter Switch; Short Circuit Protection - YORKVILLE AP4020 Owner's Manual

MODES
The AP4020/4040 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 & B inputs are paralleled
• Each gain control adjusts the signal level for its respec-
tive 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
• 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 & 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 AP4020/4040 features a specially designed subsonic
filter which effectively blocks potentially destructive energy in
the band below 40 Hz. The filter provides a 12 dB/octave.
skirt below 40 Hz. It is implemented with a two pole network
designed to minimize phase shift down to 40 Hz. We recom-
mend using this filter in conjunction with some subwoofers
and with all high power full range cabinets. With the filter dis-
abled, the AP4020/4040 is flat down to 20 Hz, and rolls off at
12dB/Oct below that.

LIMITER SWITCH

With the internal limiters activated, the AP4020/4040's
gain is continuously adjusted to fit the signal within the avail-
able 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 avail-
able dynamic headroom. With the limiters activated, all you
need to do is turn up the signal level until you start to see
some clipping. The limiters will make sure that you are getting
the maximum clean power output at all times. Setting the
switch to the IN position completely disables both limiters.
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 on and off at about 3 second intervals.
The sound may come on and off at ½ second intervals. In this
case, the fault is in the speakers or the speaker cables and
should be located and remedied. No reset of the AP4020
/4040 is required to restore proper operation. The PROTECT
LED will stay on if the amplifier has overheated. Check the
speaker load impedance and any restrictions to air flow at the
air intake or exhaust vents of the amplifier.

SHORT CIRCUIT PROTECTION

The AP4020/4040 is fully protected against all possible pas-
sive load conditions. It can operate into a dead short continu-
ously without damage. (However, we don't recommend that
you short your AP4020/4040 "just for fun." Shorts do create a
lot of stress on the output devices). The output stage uses a
unique triple slope VI-limiting scheme which is sophisticated
CAUTION: The AP4020/4040 can deliver over 2400 Watts of power into a bridged load. Yorkville's own high power speaker systems have
circuit-breaker protection built in. Although these speakers will protect themselves, they are unlikely to be damaged by a bridged
AP4020/4040 . 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
capability. Yorkville's Two Year Unconditional Warranty does not cover any consequential damages to non-Yorkville equipment. Please con-
sider these facts carefully before you choose to run your AP4020/AP4040 in Bridge Mode!
2
enough to remain inert during transient currents in excess of
100 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 AP4020/4040'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 AP4020/4040 overheats, the
signal will be sporadically cut off and the PROTECT LED will
stay on. The AP4020/4040 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 most installa-
tions. 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 AP4020/4040 is factory equipped with a fan filter
mounted on the air-intake grill located on the amplifier's front
panel. Regular cleaning of this filter will increase the amplifi-
er'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 environ-
ment. Replacement filters are inexpensive and can be ordered
through Yorkville dealers. The foam filter should be removed
if a regular inspection schedule is not going to be followed.
The amplifier can operate without the filter in place, but the
amplifier should be cleaned internally by a qualified service
technician when dust is visible on the heatsink fins.
Note: In an unusually dusty location, without regular filter inspec-
tions, removing the foam filter can extend the operating time before
thermal shutdown could occur. At that time, the internal heatsinks
should be cleaned thoroughly.