No, dual mono and balanced isn't the same at all.
Dual mono refers to two separate and unrelated signals, for example two mono microphone outputs from different locations. Stereo is two microphone outputs at the same location. I don't think you should refer to an amplifier as being dual mono although in the sense that the left and right hand channels are handled separately, all stereo amplifiers are dual mono as well.
Balanced/unbalanced refers to how the signal at the input or output on each channel is referenced to earth. You could think of this as meaning that in the balanced case on each channel the signal on one wire goes positive from earth while at the same time the signal on the other wire goes negative to earth. In the unbalanced case on each channel one wire is earth and the other carries a signal which goes both positive or negative from earth. Balanced connections are usually used where there is a need to exclude heavy interference, for example on a long cable run.
In any case, as has been said already, the 252 isn't a balanced amplifier.
Best
David
