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THEORY OF OPERATION
Amplifier Operating States (continued)
The order is pin 4 = MSB, pin 6 = LSB. For example, if pins 4, 5 and 6 measured high (+5V),
high (+5V), low (0V), you would be in state 6. Some of the states are transitioned through so
quickly that you would need a storage scope to verify operation in that state (ex.: state 4). Below
is a brief description of the states:
State 0 Amps and speaker relay OFF-waiting for Wakeup and/or Amp On command.
State 1 Delay- Wakeup received, wait 1 second for rail voltages to stabilize.
State 2 Test supply rails - return to state 0 if out of range. If OK, set to 70V or 100V mode
according to rail voltages.
State 3 Un-Mute (turn-on) amplifier (speakers off). Return to state 0 if Off command received.
Wait 1 second, but go to state 6 immediately if high frequency input detected.
State 4 Test for power OK, DC, high frequency, overheat, etc. + Tripath faults. Go to state 5 if
OK. State 6 if not OK.
State 5 Normal operation - Set speaker relay On (amp still running). Reset retry count to 0.
Watch continuously for Off commands or any faults.
State 6 Retry state. If retry count = 6, go to state 0. Mute amp, set relay Off. Add 1 to retry
count. Wait 2.5 seconds, then go to state 3.
DSP Theory of Operation
1. Overview
The 4400’s DSP section consists of five boards manufactured as a single panel. Unregulated
power is distributed to the boards and each, except the flash card daughterboard, contains its
own regulators. The DSP board contains the 56K DSP and the 80C251 host processor along
with its subordinate PIC processor for peripheral control. This board also carries the audio
codecs and their associated analog circuitry. Two audio inputs are line level and two may be
configured for 0 to 60 dB of gain. The direct input bypasses the DSP and codecs and allows a
signal to directly drive the amplifier system. A ribbon cable transports the audio output signals,
various control and monitoring signals, and raw power between the amplifiers/power supply and
the DSP system.
A flash memory chip that holds the host operating program and system configuration informa-
tion is mounted on a small card that plugs into the processor board. The LED board holds the
front panel indicator LEDs, standby button, and the USB interface connector. The wall plate
connectors, contact closure input, direct audio output, and music on hold output are on the Wall
Plate Sense board at the back of the unit. The Auto-Volume Mic Sense board is mounted above
the Wall Plate Sense board and also contains the RS-232 connector.
When the system is on, it can be in one of two states: standby or operating. When the system is
in standby, the host and peripheral processors are powered up and functioning as are the LED
and Wall Plate Sense boards. The +/-180V main power rail voltages on the amplifier boards are
also powered up when in Standby mode. The power to the Tripath module, the Auto-Volume
Mic Sense board, the DSP section and the analog I/O circuitry and codecs is shut down. When
you bring the unit out of standby all sub-systems are powered.
Summary of Contents for FREESPACE 4400
Page 87: ...87 Circuit Board Layout Diagrams Figure 12 DSP PCB Top Etch Board Layout Diagram ...
Page 88: ...88 Circuit Board Layout Diagrams Figure 13 DSP PCB Bottom Etch Board Layout Diagram ...
Page 90: ...90 Circuit Board Layout Diagrams Figure 18 Amplifier Upper PCB Top Etch Board Layout Diagram ...
