I N S T A L L A T I O N I N S T R U C T I O N S
4.31
13.5 Use of an Isolation Transformer to convert an Unbalanced
Source into a Balanced Source
In some situations, an isolation transformer is required for RF or ground loop isolation where
the source output is unbalanced. The isolation transformer must be impedance matched to
BOTH the source and the console.
To perform the matching, you must refer to the data sheet for the source device and find the
output impedance. That will be Rseries as shown in the diagram. Select an audio isolation
transformer with a specified impedance. The transformer impedance will be (Ztransformer)
(+)
(-)
(+)
(-)
ISOLATION
TRANSFORMER
CONSOLE
INPUT
SHIELD
Zin > 10k
ohms
Console input
matching resistor
(Rconsole)
Signal
Electronic
Ground
ACTIVE
UNBALANCED
AUDIO SOURCE
CHASSIS
GROUND
Source Output
Matching Resistor
(Rseries)
Source Output impedance
(Rsource)
Isolation Transformer
Impedance
(Ztransformer)
Rseries = Ztransformer - Rsource
Rconsole = Ztransformer