Klark Teknik square one dynamics, Operator'S Manual

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Balanced/unbalanced audio
Square ONE Dynamics 37
Balanced/unbalanced audio
The electronically balanced input and output connections of the Square ONE Dynamics have the benefit of
high common mode rejection (CMR), which eliminates externally induced interference such as mains hum
etc. Balancing is especially useful when long cable runs are used between pieces of equipment.
CMR is the ability of a balanced input to reject the part of the incoming signal that has the same amplitude
and phase on both input terminals, referenced to ground. As a specification, CMR is usually stated as a dB
ratio at a given frequency.
Balanced audio
Balancing refers to the type of input or output signal connection. An unbalanced connection has two signal
carrying conductors; one of these is the cable shield or ground, which is used for signal return. A balanced
connection has three conductors, two for signals and a shield that is connected to earth. Neither of the signal
wires is grounded and each is driven with equal voltage but of opposite polarity; it is important that each of
these wires has the same source impedance. Because the signal conductors on the balanced connection are
at the same impedance and of opposite polarity they are better able to cancel, and therefore reject,
interference and noise pick-up. It is standard practice to use balanced connections for long cable runs, for
example, to amplifiers, or for cables carrying sensitive or low level signals, for example, microphones.
A balanced line requires electronics and typically employs connectors of the XLR and 1/4” TRS jack plug
types.
No actual circuit can ever be perfectly balanced due to inherent differences in the signal paths caused by the
fact that no two resistors or transistors are identical and the signal paths cannot exactly mirror one another.
So, each circuit can only be balanced to a certain degree. However, the difference between a balanced and
an unbalanced circuit is that the unbalanced circuit can never be balanced whereas, the circuit designed to be
balanced can be improved by careful component selection and layout.
In conclusion, unbalanced lines are more susceptible to noise so that cable runs should be short. Whereas,
balanced circuits offer good rejection of noise induced equally on both wires, that is, they offer high common
mode rejection, and allow long cable runs.
Principles of balanced audio
A balanced audio signal comprises three components:
• Hot wire: contains positive voltages.
• Cold wire: contains negative voltages.
• Ground wire: at zero volts and surrounds hot and cold wires.
A single-ended (unbalanced) signal must be converted into a balanced one. This is done by splitting the
signal in two, passing one half through the hot wire while the other is phase reversed into a negative mirror
image before being sent through the cold wire. After passing through the balanced cable, the balanced signal
is converted back using a CMR circuit. This reverses the phase of the cold (-ve) signal back to normal (+ve)
before being mixed with the hot (+ve) signal. Since any noise picked up by the cable will have the same
polarity in both the hot and cold signal wires, it will cancel itself out when the cold signal is phase reversed
back and mixed with the hot.