Just got a new power amp

kijanki

I don't see anything in specs showing fully balanced operation.  

Look here. Big clue:

Input impedance 

Unbalanced 50KΩ
Balanced 100KΩ

After balanced input, there is only one path (one amplifier).

So? You seem to not understand how a balanced amp works.

This amp looks like it's differentially balanced, a perfectly valid approach. This is taken from the data sheet you provided:

Input Stage
The balanced input section provides signal buffering and anti-aliasing filtering. The balanced configuration helps to avoid hum and noise pick- up from poorly shielded cables. An unbalanced input can be obtained by applying a short circuit
between Signal In- and Signal GND ...

Output Stage
The output stage is a full bridge topology with a 2nd order filter, thus the power output on the terminals Vo+ and Vo- is balanced ...
Warning: The balanced speaker outputs are both “hot”  (emphasis added)

@cleeds  It is amplifier with balanced input and not the "Fully Balanced Amplifier".  "Fully Balanced Amplifier" term refers to amplifier consisting of balanced input followed by two separate amplifiers - each driving one terminal of the speaker.

 

kijanki

"Fully Balanced Amplifier" term refers to amplifier consisting of balanced input followed by two separate amplifiers - each driving one terminal of the speaker.

Of course you are free to define terms for yourself anyway you like. But a "fully balanced amplifier" doesn’t require two separate amplifiers. You simply do not know what you’re talking about and your claim conflicts with the manufacturers' published literature.

An amplifier using balanced inputs, balanced circuits and providing balanced outputs is, by definition "fully balanced." It’s as simple as that.

@cleeds   This amplifier has only balanced input.  Circuitry between input and output is not balanced and output is not balanced.  Output is single-ended, with Mosfet bridge to switch "flip" direction of the speaker.

@cleeds   Input stage can be either "balanced" or "true balanced".  "True" refers to inputs that are not referenced to GND, like in instrumentation amp or transformer.
When pre output and amp input are both "true" balanced signal to shield capacitance in cable disappears, since signal is not referenced to GND.  Example of such configuration is output transformer to input transformer.

Amplifier can have balanced inputs or balanced outputs (to increase power), but "Fully Balanced Amplifier" means that balanced input section (instrumentation amp or transformer) is followed by two separate amplifiers, each driving one speaker terminal.  Such configuration helps to improve common mode noise rejection and reduces even harmonics.

That is at least how I understand it.  Other terms like "fully balanced input" are also used, not to mention "rms power".  Most of the time I understand what they mean.