Yorkville AP4K - Manuel (Page 5)

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Mono Mode
This can be achieved by using the remaining jacks to make the parallel connection. (see previous)
• Channel A & 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
• 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 AP4K features a specially designed subsonic filter which effectively blocks potentially destructive energy in the band
below 50 Hz. The filter provides a 18 dB/octave. skirt below 50 Hz. It is implemented with a three pole network designed to
minimize phase shift down to 50 Hz. We recommend using this filter in conjunction with some subwoofers and with all high
power full range cabinets. With the filter disabled, the AP4K is flat down to 20-Hz, and rolls off at 18dB/Oct below that.
Limiter Switch
With the internal limiters activated, the AP4K’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 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/Clip LED
When the amplifier is in Bridge mode, in the event of a shorted load or a load which is of too low an impedance for the am-
plifier to handle the PROTECT/CLIP LED’s 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 AP4K is required to restore proper operation. The PROTECT/CLIP 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.
2 ohm/4 ohm Mode
The AP4K is equipped with the capability of working in two different modes. If the amplifier is connected to speaker loads of
4-ohms or above, the switch on the rear panel can be set to 4-ohm mode. In this mode the amplifier will operate at a higher
voltage level and will maximize the available headroom. If you need to drive loads that are less than 4-ohms you can oper-
ate the amplifier in the 2-ohm mode. This will reduce the amount of voltage available and allow the amplifier to supply more
current without overheating. If you are driving speakers with limited power handling capability, the 2-ohm mode can also be
used to reduce the amount of power available to the speakers. (See the power chart)
Short Circuit Protection
The AP4K 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 AP4K “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 100 Amperes and phase angles of more than 45 degrees, yet is capable of pro-
tecting the output stage from damage due to accidental short circuits and improper loads.
DC Protection
In the unlikely event of the AP4K’s outputs going DC, a thyristor circuit will short the output terminals and divert all poten-
tially harmful currents away from your speakers.
Thermal Protection
When the amplifier is operating in the 4-ohm mode and an overheating condition exists, the amplifier will automatically
switch itself to the 2-ohm mode. This could happen as a result of the speaker impedance being less than 4-ohms, the ambi-
ent temperature being too high or the airflo w being restricted. This function will allow the amplifier to continue to produce
output even in adverse conditions. In the unlikely event that the AP4K overheats, the signal will be sporadically cut off and
the PROTECT/CLIP LED will stay on. The AP4K 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.