Connecting Inputs; Connecting Outputs; Mode Selection - Crest Audio FXA SERIES Manual

FXA

Connecting Inputs.

Use either the XLR or 1/4-inch input connectors on the rear to supply audio signals to your Crest Audio
FXA Series amplifier. Both connectors accept balanced and unbalanced audio connections. (The FXA
Series amplifiers are configured standard with "Pin 2 hot" on XLR inputs. Please note that some other Crest
Audio amplifiers are configured with "Pin 3 hot"). The unused connector can be used to jumper the audio
input to another amplifier input. For more information, see the sections on Balanced 1/4" (TRS) & XLR
Input Connectors, Input XLR Polarity, and Input Sensitivity.

Connecting Outputs.

Speakers are connected using 5-way Output Binding Posts. Please note that on the 5-way Output Binding
Post version of the FXA4801, two pairs of 5-way binding posts are provided for each channel, so that paral-
leling of speakers is possible.
For more information, see the Output Connectors and Mode Selection sections.

Mode Selection.

The three-position, recessed Mode Select switch (located on the rear panel) configures the amplifier for
either Stereo, Parallel or Bridged Mono Mode. Amplifiers are factory-configured for Stereo Mode.
Stereo Mode.
In Stereo Mode, both channels operate independently, with their input attenuators controlling their respec-
tive levels. Signal at Channel A's input produces output at Channel A's output, while signal at Channel B's
input produces output at Channel B's output. Recommended minimum nominal load impedance for stereo
operation is 2 ohms per channel. Either the 1/4" (TRS) inputs or the XLR inputs may be used.
Parallel Mode.
When set to Parallel Mode, a signal applied to Channel A's input will be amplified and appear at outputs for
both Channels A & B. Either the 1/4" (TRS) input or the XLR input on Channel A may be used.
Bridged Mono Mode.
Bridged Mono Mode straps both amplifier channels together to make a very powerful, single-channel
monaural amplifier. One channel "pushes" and the other "pulls" equally, doubling the power over that of
either channel alone. Signal is applied to the Channel A input only. Both attenuators are used to control sig-
nal level; in addition, both must be adjusted to the same setting. Either the 1/4" (TRS) or XLR input may be
used. NOTE: The channel B input connectors (XLR and/or TRS) may be used to "loop thru" the channel A
signal when in parallel or bridged mono mode.
Use extreme caution when operating the amplifier in Bridged Mono Mode. Never ground either side of the
speaker cable when the amplifier is in Bridged Mono Mode; both sides are "hot." If an output patch panel
is used, all connections must be isolated from each other and from the panel. The recommended minimum
nominal load impedance in the Bridged Mono Mode is 4 ohms, which is the equivalent to driving both
channels separately at 2 ohms. Driving bridged loads of less than the recommended minimums will activate
the IGM circuitry, resulting in a loss of power, and may also lead to a thermal protect condition.
See figures on page 11 showing output connection information.
Page 10 Crest Audio FXA Series Power Amplifiers
Models FXA601, FXA901, FXA1201, FXA2401, FXA3601, FXA4801