Phonic MAR1, Service Manual

Page: 4 / 23

3
MAR 1 Power Amplifier
Front Panel Description
1. Gain Controls
These two knobs are the level controls for
Channel one and two respectively.
Turning clockwise will increase its gain,
and counter clockwise will decrease its
gain. Please always power-up with the
volume all the way down, and increase
volume slowly to make sure that no
conditions exist which could annoy your
audience or harm your speakers.
2. Protect LED Indicator
The MAR1 features several types of
protection to prevent damage to the
circuitry during turn-on or fault conditions.
If the LEDs light up, this indicates that one
of the various protections is safeguarding
the different sections of the amplifier and
in these cases, the power output is
normally switched off until normal
operating conditions are restored.
l
Loudspeaker protection: in the event
of malfunction, a sensor located on
the power outputs is able to break the
circuit avoiding that current peaks
reach the speakers and damage
them.
l
Thermal protection on the heatsink: If
the amp overheats, thermal shutdown
protects the circuitry until the
temperature is reduced to a safe
level.
l
Short circuit protection: The Protect
LED Indicator will also light up if the
speaker terminals are short circuited,
or the impedance of the load is too
low. In these circumstances, the
Protect LED will stay on until the fault
condition is rectified.
Some protection situations require the
amplifier to be switched off and then
back on for normal operating
conditions to be restored.
3. Clip LED Indicator
The LEDs light up at clipping status,
whenever any conditions occur that could
leak to non-linearility, such as an out-of-
spec load and waveform distortion.
Because of the MAR 1’s ability to enter
and exit clipping with as few audible
artifacts as possible, you may not hear
any distortion even if the indicator flashes.
In general, a few flashes every now and
then will not be a problem. However, if
the LEDs flash often or remain on for any
extended period of time, then turn down
the volume controls to reduce the signal
level going to the MAR 1. If this doesn’t
5
1
2
3
4