owners manual / guide d' operation - Yorkville Sound

DAISY CHAINING
GROUND STRAP
BRIDGED OPERATION
OWNERS MANUAL / GUIDE D' OPERATION
In large installations it is often necessary to operate many amplifiers in parallel. Several
AUDIOPRO 3000 may be paralleled by patching from the unused input jack of the first
amp to the second amp’s input, and so on down the line. The original source must drive
all of the amplifiers. Eighteen AUDIOPRO 3000 channels would present a load of about
600 Ohms. Any source capable of driving a 600 Ohm line to +15 dBm should be able
to drive this load with no problem.
For best results, daisy chaining should be done with balanced patch cords. Ground
loop hum can be eliminated by lifting the ground straps of all but the first amplifier in the
chain.
Removing the ground strap on the rear panel will decouple chassis ground from circuit
ground. Safety (“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 somewhere else in your system. Don’t just doctor the symptom
by lifting grounds: Fix the cause by making sure that the proper electrical wiring safety
regulations have been adhered to.
Historically, bridged mode operation was a means of getting high power from medium
power amplifiers. The AUDIOPRO 3000 delivers more power from one channel than
most other amps deliver when fully bridged. Bridging the AUDIOPRO 3000 will
reproduce music with a headroom of about 4500 Watts into a 4 ohm load! We don’t
know of any subwoofers that can handle such power. We recommend that you
carefully check the ratings of your speaker system against the power specifications
listed in this manual before you consider bridging the AUDIOPRO 3000.
We have purposefully made it a little difficult to bridge the AUDIOPRO 3000. You need
to construct a special crossed-phase balanced cable. If your input cable is a balanced
XLR, you will need a stereo phone cable with the ring connection of one end going to
the tip of the other end, and the ring of that end going to the tip of the first end. If your
input cable is a phone plug, then you need to make an XLR patch cord with pin 2 of one
end going to pin 3 of the other, and pin 3 of that end going to pin 2 of the first end. See
Fig, #3. Connect the special cable from channel “A” to channel “B”. Connect the input
to your AUDIOPRO 3000 to channel “A”. Put the STEREO/MONO switch in STEREO
position. Connect your speaker between the two RED binding posts. (The resulting
phase polarity is marked on the panel).
You MUST set both front panel gain controls to the same position for bridged operation
to work properly. Failure to do this will result in premature current limiting and will
produce less power than is produced in non bridged mode's.
Again a word of CAUTION: Yorkville’s own high power speaker systems have circuit
breaker protection built in. Although they may shut down, they are unlikely to be
damaged by a bridged AUDIOPRO 3000. However, many other speaker manufacturers
make high power cabinets with no protection features whatsoever. Yorkville Sound
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