VCA Control
An external pot (500 ohm to 1K) can be connected to the ACM120XL for remote control of the master level. While a
1K pot can used, better results (smoother volume adjustment) can be obtained by using a 500 ohm pot. The external pot
is governed by the master level of the amplifier allowing the installer to set the volume, then lock the amplifier in a rack
leaving the user with just a master volume control that cannot go beyond the level set on the master (front panel) control.
Connection is via a 2 wire terminal strip on the rear panel of the amplifier.
Tone Generator
The ACM120XL includes a 4 tone generator module featuring Alert, Evacuate, Pre-Announce and Bell tones. All 4
tones can be activated individually using the rear panel terminal strip. Shorting “Common” to the relevant tone name
will activate that particular tone. The volume level of the tone is set via an internal pot (R63) which is located to the far
right (when looking from the front) of the front mixer PCB. The pot is labelled R63 and sets the level of all 4 tones.
Please note that the level of the tones is not affected by the “Master” knob on the front panel.
When any of the 4 tones are activated, inputs 4 to 8 are muted. Inputs 1, 2 and 3 on the other hand will mix with the tones
and can be used at the same time.
Insert Point
The ACM120XL includes an Insert Point to allow for connection of signal processors such as equalisers, compressors
or Feedback Exterminators. The Insert Point is located (electronically) between the mixer and power amplifier sections
of the ACM120XL. It allows for the “mixed” output of the ACM120XL to be processed externally and then returned to
the power amplifier section of the ACM120XL. The Insert Point is a 3 conductor (Tip, Ring, Sleeve) socket which
accepts a standard stereo 6.35mm (1/4”) jack. The one jack allows for signals to be “sent” to the processor and then
“returned” to the power amplifier. The connections are:
Tip - Amplifier in. This is the return signal from the processor
Ring - Mix Output. This is the signal from the mixer stage which is to be sent to the processor
Sleeve - This is the ground connection.
When an external processor is used via the insert point, it only affects the power amplifier section of the ACM120XL.
The tape output remains unprocessed.
Tape Output
The ACM120XL include a tape recorder output via dual RCA connectors. Although the output signal is mono, dual
RCA’s are provided to allow for easy connection to domestic or professional tape recorders.
The output level of the tape output is governed by the 8 input controls of the ACM120XL. The front panel master
control does not affect the tape output. In a practical situation, this allows for “on the fly” changes to the power amplifier
level (to turn the PA system up or down) without affecting the signal being recorded.
Line Output
A 3 pin male XLR socket is provided to allow for connection to additional power amplifiers. The line level signal is the
mixer output of the ACM120XL allowing this “mixed” signal to be split to other amplifiers. This is most commonly
used when more power (than the 120 watts of the ACM120XL) is required. In this situation, a standard microphone lead
is used to connect the line output of the ACM120XL to the line input of a power amplifier. The speaker load then needs
to be split into two (one for each amplifier) making sure that each amplifier is driving no more than it’s recommended
load.
The line output is a balanced 700mV signal which can be used to connect (daisy-chain) up to 6 power amplifiers. If
more than 6 amplifiers are required, a distribution amplifier is recommended.
XLR Microphone Inputs
The ACM120XL includes 8 microphone and line inputs. The microphone inputs are via 3 pin XLR female sockets. The
microphone inputs are 200 ohm and are suitable for a wide range of dynamic or electret microphones. When using
electret microphones, phantom power should be enabled for those particular inputs. Phantom power (15v DC) is avail-
able on all XLR inputs and can be switched on or off per channel. To enable phantom power on a particular input
channel, simply flip dip switch 3 (for that channel) to the on position.
