General Checklist; Optical Connections; Switching The Amp On; Protection Mode - SPHINX Project Twelve Service Manual

SPHINX

6. GENERAL CHECKLIST

Before you test or service the Project Twelve
please check the following items. They will give
information about the current status of the amplifier.
Note: The Project Twelve will become warm, so
correct placement is critical. Do not position it on
top of or close to other heat-radiating equipment
(such as other power amps) or in direct sunlight.
Please ensure unrestricted ventilation around
the component.

Optical connections

The optical CONTROL IN (4.) is light-sensitive. A
strong light source might therefore activate the
CONTROL function and switch the Project Twelve
to Standby.
While this mode has priority the amplifier can not
be activated with the Standby switch at the front
panel.
Before you start connecting equipment it is always
wise to check whether all the mains cables of all
components are disconnected from the mains
outlets!
This will prevent any damage to the loudspeakers
and amplifiers caused by incorrect wiring or
settings.
Connect the mains cable after you have connected
all other components in the system and have
double-checked all connections.
If you use more than one Project Twelve connect
hem all to the same mains outlet and phase.

Switching the amp on

Before you switch the power amp on you should
always first:
•
connect a pre-amp
•
connect the pre-amp's Control Out to the power
amp's Control In
•
or place the dummy plug in the Control IN
connector of the power amp.
After switching the amplifier ON the red LED (1.)
will first blink slowly (1x per second) and then will
light continuously.
The amp is now in Standby mode.
Pressing the Standby-button (2.) will activate the
amplifier and the LED turns to green.
Project Twelve Service Manual

Protection mode

If - after switching on - the red LED (1.) blinks
rapidly (2x per second) this indicates that the
protection mode is active.
This may be caused by one of the following
problems:
1. The operational temperature exceeds 70 °C.
2. The output DC-offset exceeds +/- 350 mV.
3. The output is shorted (current-limiter active)
Warning!
The output Short-circuit protection will be
activated at output currents of over 27A. At
lower output currents (AC or DC) the amplifier
has no direct protection. At continuous large
currents, the temperature protection will take
over.
4. Power supply voltage is wrongly connected or
low (for correct voltage see underside of PJ 12)
The protection mode will do the following things:
1. Disconnect the amplifier output.
2. Disconnect the amplifier input.
3. Reset the bias current to 0 mA.
The protection mode can only be deactivated by
switching the amplifier off with the Mains Switch (6.)
and leave it off for at least 30 seconds.
If the amplifier is switched on again within those 30
seconds the protection mode will automatically be
activated.
Note: This also happens if the amplifier worked
properly before switching it off!

Cables

Always use loudspeaker and audio cables and
connectors of the highest quality.
Siltech cable is used throughout internally and we
recommend using this same cable for all external
connections.
If you have the choice between longer loudspeaker
cables or longer audio cables, choose the latter
(cables between pre-amp and power amp will
cause the least signal quality loss).
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