Stereo Mode
• Channel A and B inputs are separate.
• 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 AP2020 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
disabled, the AP2020 is flat down to 20 Hz, and rolls off at
12dB/Oct below that.
Limiter Switch
With the internal limiters activated, the AP2020’s gain is con-
tinuously 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 head-
room. 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 com-
pletely 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 AP2020 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 AP2020 is fully protected against all possible passive load
conditions. It can operate into a dead short continuously with-
out damage. (However, we don’t recommend that you short
your AP2020 “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 enough to
remain inert during transient currents in excess of 50 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 AP2020’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 AP2020 overheats, the signal will
be sporadically cut off and the PROTECT LED will stay on. If
further heating occurs, due to some malfunction, an internal
thermal breaker will interrupt the primary circuit. There is
no visible indication of this rare condition. The AP2020 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 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 AP2020 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 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 inspection schedule is not going to be followed.
The amplifier can operate without the filter in place, but a
qualified service technician should clean the amplifier inter-
nally when dust is visible on the heatsink fins.
Note: In an unusually dusty location, without regular filter
inspections, removing the foam filter can extend the operat-
ing time before thermal shutdown could occur. At that time,
the internal heatsinks should be cleaned thoroughly
Clip LEDs
The CLIP LEDs on the front panel will visibly indicate any sig-
nal excursion beyond the dynamic headroom of the amplifier.
Reliability
The AP2020 is designed and manufactured by Yorkville
Sound. Each unit undergoes a thorough, temperature cycled
burn-in period, and each circuit is tested by both manual and
sophisticated computer controlled equipment which is capable
of identifying any deviation from the design center parameters.
The design of the AP2020 is conservative with respect to the
power handling capabilities of the output devices. The topol-
ogy guarantees that thermal stress not secondary breakdown
will set the limits of operation, while the computer optimized
heat dissipation system insures that excessive thermal stress will
not occur. Yorkville’s reputation as a manufacturer of reliable
equipment will be further enhanced by the AP2020.
CAUTION: The AP2020 can deliver over 2100 Watts of power into a bridged load. Yorkville’s own high power speaker systems
have circuit-breaker protection built in. These speakers will protect themselves and thus are unlikely to be damaged by a bridged
AP2020. 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 AP2020 in Bridge Mode!
