Australian Monitor
Operation 13
Your signal source (i.e. the equipment feeding the
amplifier) should have an
output impedance
of 600
Ohms or lower to avoid unwanted high frequency
loss in the cabling.
Input overload occurs at +20.5dBu (8.25 volts).
Hum Problems
Most equipment is designed for minimum hum when
used under ideal conditions. When connected to
other equipment, and to safety earth in an electrically
noisy environment however, problems will often
occur.
The three "E"s of hum and hum related noise which
can plague your audio system are:
a) Electrostatic radiation,
b) Electromagnetic radiation, and
c) Earth loops
Electrostatic
radiation capacitively couples to
system elements causing an interference voltage
that mainly affects higher impedance paths, such as
amplifier inputs. The source is generally a nearby
high voltage such as a mains lead or a speaker lead.
The problem can usually be reduced by moving the
offending lead away, or by providing additional
electrostatic shielding (i.e. an earthed conductor
which forms a barrier to the field).
Electromagnetic
radiation induces interference
currents into system elements that mainly effect
lower impedance paths. Radio transmitters or stray
magnetic fields from mains transformers are often
the cause of this problem. It is generally more difficult
to eliminate this kind of interference, but again,
moving the source away or providing a magnetic
shield (i.e. a steel shield) should help.
Earth loops
can arise from the interfacing of the
various pieces of equipment and their connections to
safety earth.
This is by far the most common cause of hum, and it
occurs when source equipment and the amplifier are
plugged into different points along the safety earth
where the safety earth wiring has a current flowing in
it. The current flowing through the wire produces a
voltage drop due to the wire’s resistance. This
voltage difference between the amp earth and
source equipment earth appears to the amplifier's
input as a signal and is amplified as hum.
There are three things you can do to avoid earth loop
problems:
Ensure your mains power for the audio system is
“quiet” i.e. without equipment on it such as air-
conditioning, refrigeration or lighting which may
generate noise in the earth circuit.
Ensure all equipment within the system shares a
common ground/ safety earth point. This will
reduce the possibility of circulating earth currents
as the equipment will be referenced to the same
ground potential.
Ensure that balanced signal leads going to the
amplifier are connected to earth at one end only.
Signal Ground-Lift Switch
When proper system hook-up has been carried out,
you may still have some hum or hum related noise.
This may be due to any of the previously mentioned
gremlins.
Your
Synergy
Series amplifier has a “Signal Ground Lift”
switch which disconnects the input ground wiring
from the amplifier. A substantial drop in hum and or
hum related noise can result from judicious use of
this switch.
NOTE
If the input ground lift switch is used you must ensure
adequate shielding of the input wiring. If the signal
source equipment does not provide adequate
shielding (i.e. a definitive connection to ground) you
must disconnect the shield from the input
connector's ground pin (Pin-1) and re-connect it to
the "drain" contact on the input connector. This will
ensure the shield on your input wiring actually goes
to the amplifier chassis and subsequently to earth.
DO NOT CONNECT PIN-1 DIRECTLY TO THE
DRAIN CONNECTION.
You will defeat the amplifiers internal grounding
scheme and possibly cause instability to the
amplifier.
Always ensure that your amplifier is
off
and the
attenuators are
down
when you engage this switch.
This switch should only be used when the amplifier is
operated from a
balanced
signal source.
NOTE: Be wary of
quasi-balanced
outputs, these
are often no more than floating
unbalanced
outputs.
4. Operation
IMPORTANT
All signal source equipment should be adequately
earthed. This not only ensures
your
safety but
everybody else's as well. Faults can and do occur in
mains connected equipment where the chassis can
become “live” if it is not properly earthed. In these
instances the fault in a “floating” (ungrounded) piece
of equipment will look for the shortest path to ground
which could possibly be your amplifier's input. If the
fault current is large enough it will destroy the input to
your amplifier and look for the next available path,
which
may be you
!
Before making any connections
to your
Synergy
Series amplifier observe the following:
Ensure the mains voltage supply matches the
label on the rear panel of your amplifier (+/- 10%).
Ensure that the power switch is OFF (to the left -
0
)
Ensure that all system grounds (earth) are
connected from a common point. Avoid powering
equipment within a system from multiple power
sources that may be separated by large
distances.
Check the continuity of all interconnecting leads
to your amplifier, ensure that there are no open or
short circuited conductors.
Ensure that the power handling of your load
(speakers) can adequately cope with the power
output of the amplifier.
Before operating
your
Synergy
Series amplifier,
ensure that:
-
The attenuators are at the “OFF” position (fully
anticlockwise).
-
The GROUND LIFT Switch is not engaged
(should be in the “out” position).
-
The BRIDGE Switch is not engaged if you are not
running the amp in bridged mode.
Powering Up
REMEMBER
The amplifier should be the
last
piece of equipment
that you turn
on
and the
first
piece of equipment that
you turn
off
.
We recommend turning the attenuators on your
amplifier
down
when turning the unit on.
When you power up your
Synergy
Series, your amplifier
goes through an establishment period before it will
accept signal. The Inrush Current Supression (ICS)
circuit is in operation for the first 0.5 seconds. This
limits the mains current to prevent "nuisance-
tripping" of circuit breakers.
During this period you will hear a couple of relays
“click”, indicating mains is now directly applied to the
amplifier and the signal path is connected.
While the ICS circuit operates there is also a 30dB
mute on the signal input. After two seconds this mute
will release, allowing any applied signal to pass
unattenuated.
When switching the amplifier off,
wait
a couple of
seconds before switching the unit on again. This
allows the ICS circuit to reset.
Level Matching
The normal operating position for the attenuator is
the max position (fully clockwise, no attenuation). In
this position the amplifier operates at full gain.
Turning the attenuator back (anticlockwise) reduces
the input sensitivity.
NOTE:
If full power output is required you should operate
your amplifier with the front panel attenuator above
the half way (12o’clock) position, otherwise clipping
of the input circuitry and its resultant distortion will
occur before full output power is achieved.
Sensitivity
Your amplifier is a linear device operating with a fixed
input to output voltage gain (less attenuation). The
maximum output voltage swing is determined by the
applied mains voltage, load, load type and the duty
cycle of the applied signal.
The
input sensitivity
for your
Synergy
Series amplifier
when the attenuator is at maximum position (fully
clockwise) is nominally:
+4.0dB (1.23 volts in) for rated power into a 8 ohm
load.
+3.0dB (1.10 volts in) for rated power into a 4 ohm
load.
Each channel of your
Synergy
Series amplifier has a
nominal balanced
input impedance
of 30kOhms
(@1kHz) and should not present a difficult load for
any signal source.
12 Operation