Stereo Mode
• Channels A and B inputs are
separate.
• Two independent amplifi-
ers, Amp A and Amp B.
• Two loads are driven.
• Loads are connected
between the black and red posts on each channel.
Bridge Mode
• Channels A and B inputs are paralleled. Gain B
has no effect.
• Output signals are equal in amplitude but oppo-
site 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 AP1020 features a specially designed sub-
sonic 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 net-
work 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 fil-
ter disabled, the AP1020 is flat down to 6 Hz,
and rolls off at 12 dB/octave below that.
Limiter Switch
When the internal limiters are activated,
the AP1020’s gain is continuously self-
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 mid-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 clipping. The
limiters will make sure that you are getting
the maximum clean power output at all
times. Setting the switch to the Out posi-
tion 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 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 AP1020 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 restric-
tions to air flow at the air intake or exhaust vents of the amplifier.
Short-Circuit Protection
The AP1020 is fully protected against all possible passive load
conditions. It can operate with a dead short continuously without
damage. We don’t recommend that you short your AP1020 “just
for fun,” short-circuits create a lot of stress on the output devices.
The output stage uses a unique triple-slope VL limiting scheme
that is sophisticated enough to remain inert during transient cur-
rents 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 AP1020’s outputs “going DC,” a thy-
ristor circuit will short the output terminals and divert all poten-
tially harmful currents away from your speakers.
Thermal Protection
In the unlikely event that the AP1020 overheats, the signal will
be sporadically cut off and the Protect LED will stay on. If further
heating occurs, due to a malfunction, the internal thermal breaker
will interrupt the primary circuit. There is no visible indication of
this rare condition. The AP1020 is designed and tested to operate
under “worst case” conditions without shutting down, check for
blocked airflow if you experience a thermal shutdown.
Cooling
The fan draws air inward from the front and expels hot air through
the rear vents on the amplifier. This is compatible with other
Yorkville power 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 fans
in the rack to aid cooling. If there are no obstructions, secondary
cooling is not required.
Fan Filter Maintenance
The AP1020 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 fil-
ter should be removed and washed at the first sign of visible clog-
ging. 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 inspection schedule is not going to be fol-
lowed. 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 removing the foam fil-
ter can extend the operating time before thermal shutdown
could occur. At that time, the internal heatsinks should be
cleaned thoroughly.
CAUTION: The AP1020 can deliver over 800 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
AP1020. 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
consider these facts carefully before you choose to run your
AP1020
in bridged mode!
