Specifications

+ 2.2 dBu (1.0 Volts) for rated Power into a 4 ohm load.
The signal source (i.e. the equipment feeding signal to the amplifier) should have an
of 600 Ohms or lower to avoid unwanted high frequency loss in the cabling.
Input overload occurs at +19.10dBu (7.00 volts).
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 an audio system are:
a) Electrostatic radiation,
b) Electromagnetic radiation, and
c) Earth loops
radiation capacitively couples 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).
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.
can arise from the connection of the various pieces of equipment and their connection to
different 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 amplifier 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.
When proper system hook-up has been made, you may still have some hum or hum related noise. This may
be due to any of the previously mentioned problems.
The AV2.2P 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 the judicious use of this switch.
output impedance
Electrostatic
Electromagnetic
Earth loops
Hum Problems
Signal Ground-Lift Switch
10 Operation
AV2.2P