This budget-priced ($650) power amplifier has been the center of some controversy over the validity of a nulling test that Hafler devised, wherein an amplifier's output is fed, in reversed phase with its input, to yield an overall signal cancellation. Hafler contended that any amplifier that gave a perfect null must, by definition, be a perfect amplifier, and that, since the Hafler XL-280 gave by far the most nearly perfect nulling, it must be the most nearly perfect amplifier in existence.
The argument sounded…