No problem, Sfall. Explanations stated from a second perspective can only add clarity.
As Sfall said, if my hypothesis is correct the use of the INA134 can be thought of as an adapter. And it could be viewed as analogous to the many designs having unbalanced internal signal paths in which a balanced pair of output signals is created by means of an op amp configured as an inverter. Is that an ideal approach? No. But it is a simple and inexpensive way of providing a feature that can be useful in some systems.
Regards,
-- Al
Georgehifi 3-12-2017Some fully balanced architectures will not work properly unless they are provided with a balanced pair of signals. For example, some or all ARC Reference series power amplifiers, which do not provide RCA connectors, are designed such that only half of their balanced signal path will see a signal if their XLR connector is provided with a signal on pin 2 but pin 3 is grounded. In that situation the result would be a drastic reduction in power capability, as well as various adverse sonic consequences. So in this case there may be a more important reason for the approach I’ve envisioned than just adding gain for the RCA input.
Why sacrifice sound quality of the rca for the sake of the same gain.
As Sfall said, if my hypothesis is correct the use of the INA134 can be thought of as an adapter. And it could be viewed as analogous to the many designs having unbalanced internal signal paths in which a balanced pair of output signals is created by means of an op amp configured as an inverter. Is that an ideal approach? No. But it is a simple and inexpensive way of providing a feature that can be useful in some systems.
Regards,
-- Al