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HSP SERIES INSTALLATION AND OPERATION MANUAL
INSTALLATION (CONT)
Hum Problems
Most equipment is designed for minimum hum when used under ideal
conditions. When connected to other equipment, and to a safety earth in an
electrically noisy environment, problems may occur.
The three ”E”s of hum and hum related noise which can plague your audio
system are:
a) Earth loops
b) Electromagnetic radiation
c) Electrostatic radiation
Earth loops can arise from the interfacing of the various pieces of equipment
and their connections to various safety earths.
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 through 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 the 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 connecting to the amplifier are connected
to earth at one end only.
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.
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 HSP 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.
•
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.
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.
Sensitivity
The input sensitivity of your HSP amplifier when the attenuation pot is at
maximum position (fully clockwise) is nominally:
1Vrms for rated power into a 4 Ohm load
Each channel of your HSP amplifier has a nominal balanced input impedance of
20kOhms (@1kHz) and should not present a difficult load for any signal source.
Your signal source (i.e. the equipment feeding signal to the amplifier) should
have an output impedance of 600 Ohms or lower to avoid unwanted high
frequency loss in the cabling.