Specifications

RMa750 Programming Definitions Monday, 10 July 2000
page 2
as an early warning system as well. A fault from the in/out detect circuit will pass through an
internally selectable link which will either have the amplifier disconnect the offending channels
relay or have the program (via the control system) open the output relay of the offending channel.
The biggest problem for in/out detect is that clipping is essentially an input to output fault and the
reality is that transients (regardless of preceding signal processing) will generate an in/out fault due
to clipping. The micro on the amplifier interface has been programmed to allow a certain amount of
clipping to occur before reporting a fault. A considerable amount of time was spent to come up with
a suitable routine that took into consideration the ballistics of the status indicator, frequency and
ultimately the power handling ability of speakers envisaged to be used within the installation.
Power
The power for the CNPI/ CPI cards is sourced externally from the amplifiers and is required to be
supplied by the CRESTNET II/AXLink network. Though most of the interfacing to the cards is
powered internally by the amplifier and provides very little loading to the network, there is some
obvious loading that should be considered.
1) To enable the use of a remote power up/down facility, the CNPI/ CPI card has to switch a
high current relay within the amplifier.
2) The indicator for Remote Power enable/standby requires power from the CRESTNET
network.
We should consider 1mA per input and output, 20mA for the Remote Power LED, 40 mA for the
remote power relay on a Crestron system and 80mA for the remote power relay on an AMX system.
The Quiescent current draw of the CNPI card is approximately 100mA and 25mA on a CPI card,
thus a total of around 200mA minimum should be allowed for per CNPI/ CPI card within this
system. The loading of all the CNPI/ CPI cards for the amplifier system could be substantial and the
high level of current can cause substantial voltage drops over long cable lengths so booster type
power supplies should be located close to the amplifiers to minimise insertion loss type problems.
Ground
Grounding for the system is crucial. The amplifier has many ground schemes, one for mains power
and the high current outputs, one for input signal, one for pre-amps and a separate one for the
control system to amplifier interface. The control system earth connecting to each amplifier is not
connected internally to the amplifiers grounding schemes. The CNPI/ CPI card is resistively
isolated to the amplifier and the amplifier’s interface. The control system earth/ground must be at
the same ground potential as the amplifiers. A Technical type earth must be near the amplifiers and
the system should attain “STAR” grounding to this point!!!! Make sure you earth the booster power
supplies - they are not to be allowed to float. Ensure this before anything is ever turned on!!!!!!!
NOTE: If Signal ground lifting is to be used, suitable shielding of the input still needs to be
maintained. If Pin-1 on the interconnecting XLR (source equipment) is all you are relying on, you
may be in trouble as the source may not be providing a true ground for the shield (you should check
this out). You must ensure proper shielding.
The amplifier is supplied with a 4 pin Phoenix type data connector (similar to the ones Crestron and
AMX utilise). We will be supplying the connecting in line plug as well. The connectors are Phoenix
branded where the panel mount male socket is a:
DFK-MSTB 2.5/4-G-5.08,