7
3.4. Input signal connections
The signal input connectors are of XLR-3 type (16), electronically balanced. The pin
assignment is as follows:
1.- GROUND
2.- PHASE (signal in phase with the output)
3.- NON PHASE (signal in opposite phase with the output)
The input connections for a balanced or unbalanced sound signal are as Fig. 2.
The “STK OUT” outputs (15) are in parallel with the inputs and are used to supply the
same input signal to other amplifiers or sound systems. The input impedance is 20K
Ω
(balanced)
with a nominal input sensitivity of 1V (0dBV). This impedance makes possible to parallel several
amplifiers without loosing audio quality.
The input circuit has an electronic protection against overloads of 80Vpp (permanent)
and 250Vpp (short moments). There is an RLC radiofrequency filter that avoids possible
intermodulations and also protects the treble loudspeakers. The rising time of the input signal has
been optimized for a very low TIM.
3.5. Output connections
The “OUTPUT” section on the back panel is provided with Speak-on connectors (9).
To operate the amplifier on BRIDGED mode, place the “STEREO BRIDGE” switch (13) to
the “BRIDGE” position. The correspondent Led on the front panel will shine. The input signal must
be connected to the channel I connector while the output signal will be present on the Speak-on
connector labelled as “BRIDGED”.
The phase shifter used for BRIDGED mode is electronic and is placed in the input
circuit, thus lessening the distortion and increasing the phase margin. When operating on
BRIDGED mode, the signal input is made through channel I input and the corresponding input
attenuator is operative while the one of the other channel is not.
The cable between the amplifier outputs and the loudspeakers must be of good quality,
enough section and as short as possible. This is very important when the distance is long and the
load is low (4-8
Ω
). We recommend a section of 2.5mm
2
or more for distances up to 10m and a
section of 4 or 6mm
2
for longer distances. An easy way to known the required section, assuming
a 4% loss, is:
Length in meters
Section in mm
2
=
Loudspeaker impedance in
Ω
3.6. Subsonic filter
This filter cuts off inaudible frequency components which when amplified suppose a
risk of damage to the low frequency speakers as they generate excessive excursions of the
woofer's diaphragm. The filter, which has a Butterworth shaped response with 18 dB/oct slope
can be internally set to three different cut-off frequencies or switched off completely (20, 30,
40 Hz and OFF). The amplifiers are delivered with a cut-off frequency of 20 Hz. To select a
different cut-off frequency, refer to figure 3.
Summary of Contents for PAM1100
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