3
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.
Clip LEDs
The CLIP LEDS on the front panel will visibly indicate any signal excursion beyond the dynamic headroom of the amplifier.
Reliability
The AP4K 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 iden-
tifying any deviation from the design center parameters. The design of the AP4K is conservative with respect to the power
handling capabilities of the output devices. The topology 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 reinforced by the AP4K.
The AP4K is not only suitable for use in both heavy duty touring sound reinforcement systems but also when high head-
room and low distortion are needed to fully reproduce the dynamic range and clarity of today’s CD recordings. It is built to
survive grueling road conditions and constant 2 ohm or 4 ohm operation. Its reliability in a fixed installation running 4 or 8
ohm studio monitors is without parallel.
Output Connections
WARNING:
When driven to full power in Bridge Mode. There is more than 200 Vrms appearing between the binding posts. This
represents a significant shock hazard and due care should be taken when making any speaker connections. Ensure that no
strands of bare conductor are exposed after inserting the speaker wire into the hole in the side of the binding post terminals.
The AP4K has 5–way binding posts and Neutrik four contact Speakon™ connectors for output speaker connections. Con-
nection to the binding posts can either be made with a banana plug inserted into the end of the post or you can insert the
wire into the side of the binding post.
There are two Speakon™ connectors. The Speakons™ are connected to the amplifier’s outputs whether the amplifier
is in stereo, mono, or bridge modes. Each Speakon™ output connector (output A and output B) is wired in parallel with it’s
respective binding posts for two channel two cable connections (figure 1).
Speakon™ output A also doubles as the A&B/Bridge connector. This Speakon™ contains both channels on one connec-
tor. This is convenient when connecting one speaker to the amplifier in bridge mode where the speaker is connected across
the positives of each amplifier output. Configure the mode switch for bridge and connect the speaker to pins +1 and +2 of
the bridge/bi-amp Speakon (figure 3).
To connect a bi-amp speaker, configure the amplifier for
stereo
and connect to the bridge/bi-amp connector but use all
four terminals in the Speakon connector which will connect A and B outputs separately to the speaker (figure 2). Connection
configurations are labeled on the back panel.
Power Output
All values are in WATTS. Measurements were made at the 0.1% distortion point. Some CONTINUOUS AVERAGE POWER
measurements required line currents greater than 15 Amps. The amplifier under test was plugged into an IDEAL POWER LINE
consisting of a REGULATED 120 VAC RMS 60 Hz pure sine wave. Ordinary AC “wall outlet” lines will always exhibit varying
and unpredictable amounts of sag. To produce objectively verifiable and accurate specifications these unknown factors must be
eliminated by using an ideal AC line. When using an ordinary electrical outlet, it will usually be possible to get 3600 Watts when
the AP4K is bridged into 8 ohms or 4 ohms. The BURST measurements use a 10 mS burst at 1 KHz with a 1/8 second pause
between bursts. The 1 KHz burst represents the maximum possible sine wave output power.
CAUTION:
The AP4K can deliver over 3600 Watts of power into a bridged load. Most of Yorkville’s own
high power speaker systems have circuit-breaker protection built in and will protect themselves under such
conditions. Please be aware that 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 con-
sequential damages to non-Yorkville equipment. Please consider these facts carefully before you choose to
run your AP4K in Bridge Mode!
