YORKVILLE A4.4 Manuel De L'utilisateur page 4

4. Driving Multiple A4.4's
In large installations it is often desirable to operate many amplifiers in tandem. Since each
channel's XLR input is internally paralleled with its phone input, you may use the remaining input
jack as an output to the next amplifier. Obviously you will need both XLR to XLR and Phone to
Phone patch cords if you are going to tandem more than two amplifiers.
NOTE: These patch cords MUST be balanced whether the input signal is balanced or unbalanced!
5. Ground Switch
Switching the ground switch on the rear panel will disconnect chassis ground from circuit ground.
Earth ground is still connected to the chassis. We do not recommend lifting the ground strap
unless you are experiencing problems with ground loop hum in multiple amplifier setups where
lifting the ground straps of all but one amplifier cures the hum problem.
CAUTION: Sometimes hum problems are an indication of improper AC wiring.. Don't just doctor the
symptom by lifting grounds. Fix the cause by making sure that the proper electrical wiring safety regula-
tions have been adhered to.
6. Modes
The A4.4 can be configured for dual-Mono, Stereo, or Bridged-Mono operation via the rear panel
Mode switch. The following is a description of each mode:
Mono Mode
• 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.
7. Subsonic Filter Switch
The A4.4 features a specially designed Subsonic Filter which blocks potentially destructive
energy in the band below 40 Hz. This filter provides a 12 dB/octave skirt below 40 Hz. It is imple-
mented with a two pole network 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 this filter disabled, the A4.4 is flat down to 20-Hz, and rolls off at 12dB/Octave below that.
8. Limiter Switch
With the internal limiters activated, the A4.4'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.
9. Protect LED
In the event of a shorted load or a load which is of too low an impedance for the amplifier to han-
dle 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 A4.4 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.
10. Short Circuit Protection
The A4.4 is fully protected against all possible passive load conditions. It can operate into a dead
short continuously without damage however, we don't recommend that you short your A4.4 "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 protecting the output stage from damage due to accidental short circuits and
improper loads.
11. DC Protection
In the unlikely event of the A4.4's output's going DC, a thyristor circuit will short the
output terminals and divert all potentially harmful currents away from your speakers.
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