General purpose audio transformers

Applications:
•Splitting
•Galvanic isolation
•Balanced-unbalanced conversion

Properties:
Flexible, with many different connection alternatives possible
Moderate copper resistance (50 Ω per section typically)
Medium signal level capability (Max 10 dBU at 50 Hz per section typically)
Excellent magnetic and electrostatic shielding
High mu cores (mu metal or amorphous strip core)

Discussion:
General purpose audio isolation transformers, as far as
impedance is concerned, can be considered as hybrids between
input transformers and output transformer.
Input transformers are used at dedicated input situations and
should present a very high impedance to the source.
They should also accept high line level signals.
Output transformers are used to drive long cable length and should
combine low copper resistance with high signal level capability.
General purpose transformers are often used in applications which
are not clearly input OR output, and where dedicated input or
output transformers are less well suited.

The most obvious applications for 1:1 general purpose transformers are audio ground isolation and balanced-to-unbalanced conversion.  This type of general purpose transformer is also used for audio splitting 1 direct + 1 isolated.

For successfully splitting 1 direct + 2 isolated, 1 direct + 3 isolated, and for MS encoding/decoding, a more complex internal winding structure is required, with separated Faraday shields and with transformer housing and core galvanically separated.  Because splitting transformers are also in-between impedance-wise they belong to the general purpose transformer category.