User manual

(4.0E) 2-1
IMPORTANT!
CAUTION!
2. E-PAC power amplifier controller
The E-PAC incorporates a power supply, single channel power
amplifier, Digital Signal Processor (DSP), all necessary protection
circuits, a remote interface, controls and indicators.
The E-PAC is housed in a 2 RU high, rugged enclosure and can be
operated as a stand alone unit. Optional accessories allow
installation of a single E-PAC in a standard 19“ equipment rack, or
a pair mounted side by side.
2.1. Digital controller
The controller incorporated in the E-PAC is based on a Digital
Signal Processor, DSP, utilising sigma-delta signal conversion and is
pre-programmed for E3, E9, C6, E12-SUB, E18-SUB and MAX
(linear mode). These configurations can be selected by setting DIP-
switches on the rear panel.
The signal processing includes correction of the frequency
response, a high pass filter, limiting and complex protection circuits
that model loudspeaker cone displacement and voice coil
temperature.
The DIP switch settings are specific to the characteristics of
individual loudspeakers, affecting the frequency response and
maximum output level. To ensure optimum performance and
prevent damage to system components each type of loudspeaker
has to be used in conjunction with a suitably configured E-PAC.
Delay settings up to 170 ms can be programmed into the
controller using a RIB, Remote Interface Bridge, in conjunction with
a PC running d&b ROPE control software.
The E-PAC digital signal processing circuits introduce a processing
delay of 0.7 ms into the signal path, equivalent to a sound path
length of 24 cm. If two identical loudspeakers are driven by digital
(E-PAC) and analogue (P1200A) controllers respectively, the 0.7 ms
delay of the E-PAC effectively positions its respective loudspeaker
at a distance of 24 cm behind the loudspeaker driven by the
P1200A. Where the two loudspeakers form an array this will lead
to an increase in comb filtering and unpredictable coverage
patterns. If the distance between the cabinets is much greater than
the path difference of 24 cm, this effect becomes negligible.
Please note that all digital signal processing equipment used in the
signal path will delay the signal. For example digital equalizers
have a typical processing delay of about 3 ms.