That circuit only works if the positive current equals the negative current. For example if you try to draw slightly more positive current than negative current, there's no place for the excess current to flow from the ground to the 15V supply.The 2SC1384 and 2SA684 are 1A a pair of bjt, if you could find some similar or bigger than 1A then you could use them.
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Here's a circuit that will properly work with unbalanced loads.