Yorkville Sound AP812 User Manual

Power Amplifier - General

The

AP812/818 has a built-in 800 watt stereo power amplifier. Each channel has an

input sensitivity of

+4 dBv (1.4 volts RMS) for full-power output and each can deliver

over

400 watts into a 4 ohm speaker load. These amplifiers incorporate computer

designed internal heatsinks and a variable-speed fan which automatically provides

quiet operation consistent with cooling requirements. Cool air is drawn into the front

of the mixer, and heated air is expelled along the bottom of the back. Even at maxi-

mum power, this arrangement results in quiet, dependable performance.

PLEASE NOTE: THE AIR VENTS AT THE FRONT AND BOTTOM REAR OF THE

MIXER ARE ESSENTIAL FOR PROPER

OPERATION. BLOCKING THE

FREE FLOW OF AIR THROUGH

THE MIXER WILL RESULT IN

SYSTEM SHUT-DOWN DUE

TO OVERHEATING. REPEATED

OVERHEATING MAY EVENTUALLY

CAUSE DAMAGE. PLEASE KEEP THE

VENTS FREE OF OBSTRUCTIONS.

Speaker Connections

Two

1/4-inch jacks and one Speakon®

connector are in parallel with each amp-channel output stage. This allows the use of

speaker cables equipped with either type of connector. For full-power applications we

recommend

14-gauge cables equipped with the Speakon® connectors. This will reduce

risk of resistance buildup. The

Speakon® system, developed in recent years by Neutrik

in Switzerland, features block-style contacts capable of handling large amounts of

power and the connectors lock down to prevent accidental kick-outs.

Connect one or two

8 ohm speakers or one (only) 4 ohm speaker to each chan-

nel. When connecting the

Speakon’s®, push them in firmly and twist in a clockwise

motion. Push the tab and twist counter-clockwise to disconnect.

User tip: To connect two (8 ohm) speakers to one or both of the AP812’s powered

output channels via the

Speakon® connectors, run a single Speakon® -equipped

cable, e.g.

Yorkville model SP2-25SS or SP2-50SS with Speakons® at both ends

(most higher-powered speaker enclosures now feature

Speakons® as well) from the

AP812/818 to one of the enclosures. Now run a second cable from one cabinet to the

next via their dual, parallel inputs.

Power Amplifier Protection

The

AP812/818’s power amplifier is protected from damage due to open, shorted or

excessively low speaker loads. It will continue to run into a low (less than

4 ohms)

overall speaker impedance or even a total short-circuit for a brief time, however the

amplifier’s defense system will be activated. First, the built-in limiter will reduce output

power levels and the fan speed may increase. Then, if the condition worsens, a thermal

protection circuit will shut the power amplifier down. When this happens, check your

system for restricted air intake/exhaust at the

AP812/818. Also check for shorted cables

or connectors and/or reduce the number of speakers being driven. In a few minutes

when it has had a chance to cool down, power amp function will resume.

User tip:
a) If the power amplifier shuts down as above, the mixer section will continue to

function. This means that, if the

AP812/818’s power amp fails to come back on

(unlikely) and you have a spare power amplifier available, you can connect it to

the

AP812/818 via the LINE OUTPUT jacks. See under PRE and POST EQ LINE

OUTPUTS for further information regarding connections.
b) Because the amplifier is also protected against open-circuit conditions, you

may use the

AP812/818 without any speakers connected, for example if you

wanted to do some recording.