unbalanced xlr input (a24) to mytek balanced output

Sometimes an XLR input is actually not differential, but there for convenience. The A23 is an example. The (-) pin on the XLR input is grounded.

In the A21 however the (+) and (-) pins are not grounded, each has a 33k impedance to ground and the difference between them is used to determine the output.

In my setup between true-balanced Bat42se and a21 there is no 6db increase via XLR connection, but between my two separate Bat components and other true-balanced devices the increase in volume  is obvious. I doubt the a21 is a true-balanced amp.

Thanks a lot for the responses. So what I gather is they are in fact true balanced connections, the signal path however is not a "true-balanced" signal path completely like hasmartos Bat42se. I gather there are very nice benefits to use XLR regardless whether they are balanced from beginning to end or not. Impedance being an obvious one. So much to learn so little time

Erik_Squires 3-13-2019
The A23 is an example. The (-) pin on the XLR input is grounded.

Erik, are you sure about that? From the manual for the A23:

The Input Stage:

The A 23’s input stage uses matched pairs of discrete JFETs arranged in a differential configuration. JFETs are ideal for the input stage because their inherently high impedance is unaffected by the impedance of source components. Differential configuration provides superior noise reduction. These precision input JFETs are also cascoded to produce the current necessary to drive the MOSFET drivers in the following stage.

Also, while grounding pin 3 of an XLR input connector (the inverted signal pin) would be appropriate in many cases if that input were driven by a balanced output that is transformer coupled, or is actively driven but is "floating" with respect to ground, it could potentially cause performance problems, or conceivably even damage over the long-term, to some components having actively driven balanced outputs. (See this thread for an example of a CD player that buzzed as a result of pin 3 being grounded by an adapter cable). Yet the manual for the A23 provides no cautions about the potential for any such issues.

Best regards,
-- Al

P.S:  Perhaps pin 3 is grounded when and only when the switch on the rear panel that selects between balanced and unbalanced inputs is set to "unbalanced."  That would make much more sense.

Best regards
-- Al